diff --git a/android/prebuilt.go b/android/prebuilt.go
index 5087b18..b674153 100644
--- a/android/prebuilt.go
+++ b/android/prebuilt.go
@@ -16,6 +16,7 @@
 
 import (
 	"fmt"
+	"reflect"
 
 	"github.com/google/blueprint"
 	"github.com/google/blueprint/proptools"
@@ -43,7 +44,10 @@
 	properties PrebuiltProperties
 	module     Module
 	srcs       *[]string
-	src        *string
+
+	// Metadata for single source Prebuilt modules.
+	srcProps reflect.Value
+	srcField reflect.StructField
 }
 
 func (p *Prebuilt) Name(name string) string {
@@ -71,11 +75,16 @@
 		// sources.
 		return PathForModuleSrc(ctx, (*p.srcs)[0])
 	} else {
-		if proptools.String(p.src) == "" {
-			ctx.PropertyErrorf("src", "missing prebuilt source file")
+		if !p.srcProps.IsValid() {
+			ctx.ModuleErrorf("prebuilt source was not set")
+		}
+		src := p.getSingleSourceFieldValue()
+		if src == "" {
+			ctx.PropertyErrorf(proptools.FieldNameForProperty(p.srcField.Name),
+				"missing prebuilt source file")
 			return nil
 		}
-		return PathForModuleSrc(ctx, *p.src)
+		return PathForModuleSrc(ctx, src)
 	}
 }
 
@@ -89,10 +98,12 @@
 	p.srcs = srcs
 }
 
-func InitSingleSourcePrebuiltModule(module PrebuiltInterface, src *string) {
+func InitSingleSourcePrebuiltModule(module PrebuiltInterface, srcProps interface{}, srcField string) {
 	p := module.Prebuilt()
 	module.AddProperties(&p.properties)
-	p.src = src
+	p.srcProps = reflect.ValueOf(srcProps).Elem()
+	p.srcField, _ = p.srcProps.Type().FieldByName(srcField)
+	p.checkSingleSourceProperties()
 }
 
 type PrebuiltInterface interface {
@@ -129,7 +140,7 @@
 func PrebuiltSelectModuleMutator(ctx TopDownMutatorContext) {
 	if m, ok := ctx.Module().(PrebuiltInterface); ok && m.Prebuilt() != nil {
 		p := m.Prebuilt()
-		if p.srcs == nil && p.src == nil {
+		if p.srcs == nil && !p.srcProps.IsValid() {
 			panic(fmt.Errorf("prebuilt module did not have InitPrebuiltModule called on it"))
 		}
 		if !p.properties.SourceExists {
@@ -172,7 +183,7 @@
 		return false
 	}
 
-	if p.src != nil && *p.src == "" {
+	if p.srcProps.IsValid() && p.getSingleSourceFieldValue() == "" {
 		return false
 	}
 
@@ -183,3 +194,28 @@
 
 	return source == nil || !source.Enabled()
 }
+
+func (p *Prebuilt) checkSingleSourceProperties() {
+	if !p.srcProps.IsValid() || p.srcField.Name == "" {
+		panic(fmt.Errorf("invalid single source prebuilt %+v", p))
+	}
+
+	if p.srcProps.Kind() != reflect.Struct && p.srcProps.Kind() != reflect.Interface {
+		panic(fmt.Errorf("invalid single source prebuilt %+v", p.srcProps))
+	}
+}
+
+func (p *Prebuilt) getSingleSourceFieldValue() string {
+	value := p.srcProps.FieldByIndex(p.srcField.Index)
+	if value.Kind() == reflect.Ptr {
+		value = value.Elem()
+	}
+	if value.Kind() != reflect.String {
+		panic(fmt.Errorf("prebuilt src field %q should be a string or a pointer to one", p.srcField.Name))
+	}
+	return value.String()
+}
+
+func (p *Prebuilt) SourceExists() bool {
+	return p.properties.SourceExists
+}
diff --git a/android/sh_binary.go b/android/sh_binary.go
index fb7446d..2855aa0 100644
--- a/android/sh_binary.go
+++ b/android/sh_binary.go
@@ -29,6 +29,7 @@
 	RegisterModuleType("sh_binary", ShBinaryFactory)
 	RegisterModuleType("sh_binary_host", ShBinaryHostFactory)
 	RegisterModuleType("sh_test", ShTestFactory)
+	RegisterModuleType("sh_test_host", ShTestHostFactory)
 }
 
 type shBinaryProperties struct {
@@ -195,6 +196,7 @@
 	return module
 }
 
+// sh_test defines a shell script based test module.
 func ShTestFactory() Module {
 	module := &ShTest{}
 	InitShBinaryModule(&module.ShBinary)
@@ -203,3 +205,13 @@
 	InitAndroidArchModule(module, HostAndDeviceSupported, MultilibFirst)
 	return module
 }
+
+// sh_test_host defines a shell script based test module that runs on a host.
+func ShTestHostFactory() Module {
+	module := &ShTest{}
+	InitShBinaryModule(&module.ShBinary)
+	module.AddProperties(&module.testProperties)
+
+	InitAndroidArchModule(module, HostSupported, MultilibFirst)
+	return module
+}
diff --git a/android/sh_binary_test.go b/android/sh_binary_test.go
index c99e18c..9df769c 100644
--- a/android/sh_binary_test.go
+++ b/android/sh_binary_test.go
@@ -10,6 +10,7 @@
 
 	ctx := NewTestArchContext()
 	ctx.RegisterModuleType("sh_test", ModuleFactoryAdaptor(ShTestFactory))
+	ctx.RegisterModuleType("sh_test_host", ModuleFactoryAdaptor(ShTestHostFactory))
 	ctx.Register()
 	mockFiles := map[string][]byte{
 		"Android.bp":         []byte(bp),
@@ -48,3 +49,23 @@
 		t.Errorf("Unexpected test data expected: %q, actual: %q", expected, actual)
 	}
 }
+
+func TestShTestHost(t *testing.T) {
+	ctx, _ := testShBinary(t, `
+		sh_test_host {
+			name: "foo",
+			src: "test.sh",
+			filename: "test.sh",
+			data: [
+				"testdata/data1",
+				"testdata/sub/data2",
+			],
+		}
+	`)
+
+	buildOS := BuildOs.String()
+	mod := ctx.ModuleForTests("foo", buildOS+"_x86_64").Module().(*ShTest)
+	if !mod.Host() {
+		t.Errorf("host bit is not set for a sh_test_host module.")
+	}
+}
diff --git a/apex/apex.go b/apex/apex.go
index f683f96..f7042fc 100644
--- a/apex/apex.go
+++ b/apex/apex.go
@@ -111,6 +111,7 @@
 	testTag        = dependencyTag{name: "test"}
 	keyTag         = dependencyTag{name: "key"}
 	certificateTag = dependencyTag{name: "certificate"}
+	usesTag        = dependencyTag{name: "uses"}
 )
 
 func init() {
@@ -147,6 +148,7 @@
 	android.PostDepsMutators(func(ctx android.RegisterMutatorsContext) {
 		ctx.TopDown("apex_deps", apexDepsMutator)
 		ctx.BottomUp("apex", apexMutator).Parallel()
+		ctx.BottomUp("apex_uses", apexUsesMutator).Parallel()
 	})
 }
 
@@ -187,6 +189,11 @@
 		mctx.CreateVariations(apexBundleName)
 	}
 }
+func apexUsesMutator(mctx android.BottomUpMutatorContext) {
+	if ab, ok := mctx.Module().(*apexBundle); ok {
+		mctx.AddFarVariationDependencies(nil, usesTag, ab.properties.Uses...)
+	}
+}
 
 type apexNativeDependencies struct {
 	// List of native libraries
@@ -272,6 +279,12 @@
 
 	// List of sanitizer names that this APEX is enabled for
 	SanitizerNames []string `blueprint:"mutated"`
+
+	// Indicates this APEX provides C++ shared libaries to other APEXes. Default: false.
+	Provide_cpp_shared_libs *bool
+
+	// List of providing APEXes' names so that this APEX can depend on provided shared libraries.
+	Uses []string
 }
 
 type apexTargetBundleProperties struct {
@@ -643,7 +656,7 @@
 		dirInApex = "lib64"
 	}
 	dirInApex = filepath.Join(dirInApex, cc.RelativeInstallPath())
-	if !cc.Arch().Native {
+	if cc.Target().NativeBridge == android.NativeBridgeEnabled || !cc.Arch().Native {
 		dirInApex = filepath.Join(dirInApex, cc.Arch().ArchType.String())
 	}
 	if handleSpecialLibs {
@@ -668,6 +681,9 @@
 
 func getCopyManifestForExecutable(cc *cc.Module) (fileToCopy android.Path, dirInApex string) {
 	dirInApex = filepath.Join("bin", cc.RelativeInstallPath())
+	if cc.Target().NativeBridge == android.NativeBridgeEnabled || !cc.Arch().Native {
+		dirInApex = filepath.Join(dirInApex, cc.Arch().ArchType.String())
+	}
 	fileToCopy = cc.OutputFile().Path()
 	return
 }
@@ -727,6 +743,30 @@
 
 	handleSpecialLibs := !android.Bool(a.properties.Ignore_system_library_special_case)
 
+	// Check if "uses" requirements are met with dependent apexBundles
+	var providedNativeSharedLibs []string
+	useVendor := proptools.Bool(a.properties.Use_vendor)
+	ctx.VisitDirectDepsBlueprint(func(m blueprint.Module) {
+		if ctx.OtherModuleDependencyTag(m) != usesTag {
+			return
+		}
+		otherName := ctx.OtherModuleName(m)
+		other, ok := m.(*apexBundle)
+		if !ok {
+			ctx.PropertyErrorf("uses", "%q is not a provider", otherName)
+			return
+		}
+		if proptools.Bool(other.properties.Use_vendor) != useVendor {
+			ctx.PropertyErrorf("use_vendor", "%q has different value of use_vendor", otherName)
+			return
+		}
+		if !proptools.Bool(other.properties.Provide_cpp_shared_libs) {
+			ctx.PropertyErrorf("uses", "%q does not provide native_shared_libs", otherName)
+			return
+		}
+		providedNativeSharedLibs = append(providedNativeSharedLibs, other.properties.Native_shared_libs...)
+	})
+
 	ctx.WalkDepsBlueprint(func(child, parent blueprint.Module) bool {
 		if _, ok := parent.(*apexBundle); ok {
 			// direct dependencies
@@ -743,11 +783,6 @@
 				}
 			case executableTag:
 				if cc, ok := child.(*cc.Module); ok {
-					if !cc.Arch().Native {
-						// There is only one 'bin' directory so we shouldn't bother copying in
-						// native-bridge'd binaries and only use main ones.
-						return true
-					}
 					fileToCopy, dirInApex := getCopyManifestForExecutable(cc)
 					filesInfo = append(filesInfo, apexFile{fileToCopy, depName, dirInApex, nativeExecutable, cc, cc.Symlinks()})
 					return true
@@ -815,6 +850,11 @@
 			// indirect dependencies
 			if am, ok := child.(android.ApexModule); ok && am.CanHaveApexVariants() && am.IsInstallableToApex() {
 				if cc, ok := child.(*cc.Module); ok {
+					if android.InList(cc.Name(), providedNativeSharedLibs) {
+						// If we're using a shared library which is provided from other APEX,
+						// don't include it in this APEX
+						return false
+					}
 					if !a.Host() && (cc.IsStubs() || cc.HasStubsVariants()) {
 						// If the dependency is a stubs lib, don't include it in this APEX,
 						// but make sure that the lib is installed on the device.
@@ -1363,7 +1403,8 @@
 
 type PrebuiltProperties struct {
 	// the path to the prebuilt .apex file to import.
-	Source string `blueprint:"mutated"`
+	Source       string `blueprint:"mutated"`
+	ForceDisable bool   `blueprint:"mutated"`
 
 	Src  *string
 	Arch struct {
@@ -1392,6 +1433,14 @@
 }
 
 func (p *Prebuilt) DepsMutator(ctx android.BottomUpMutatorContext) {
+	if ctx.Config().FlattenApex() && !ctx.Config().UnbundledBuild() && p.prebuilt.SourceExists() {
+		// If the device is configured to use flattened APEX, don't set
+		// p.properties.Source so that the prebuilt module (which is
+		// a non-flattened APEX) is not used.
+		p.properties.ForceDisable = true
+		return
+	}
+
 	// This is called before prebuilt_select and prebuilt_postdeps mutators
 	// The mutators requires that src to be set correctly for each arch so that
 	// arch variants are disabled when src is not provided for the arch.
@@ -1433,6 +1482,10 @@
 }
 
 func (p *Prebuilt) GenerateAndroidBuildActions(ctx android.ModuleContext) {
+	if p.properties.ForceDisable {
+		return
+	}
+
 	// TODO(jungjw): Check the key validity.
 	p.inputApex = p.Prebuilt().SingleSourcePath(ctx)
 	p.installDir = android.PathForModuleInstall(ctx, "apex")
@@ -1478,7 +1531,7 @@
 func PrebuiltFactory() android.Module {
 	module := &Prebuilt{}
 	module.AddProperties(&module.properties)
-	android.InitSingleSourcePrebuiltModule(module, &module.properties.Source)
+	android.InitSingleSourcePrebuiltModule(module, &module.properties, "Source")
 	android.InitAndroidMultiTargetsArchModule(module, android.DeviceSupported, android.MultilibCommon)
 	return module
 }
diff --git a/apex/apex_test.go b/apex/apex_test.go
index b410425..94cf19d 100644
--- a/apex/apex_test.go
+++ b/apex/apex_test.go
@@ -29,7 +29,32 @@
 
 var buildDir string
 
+func testApexError(t *testing.T, pattern, bp string) {
+	ctx, config := testApexContext(t, bp)
+	_, errs := ctx.ParseFileList(".", []string{"Android.bp"})
+	if len(errs) > 0 {
+		android.FailIfNoMatchingErrors(t, pattern, errs)
+		return
+	}
+	_, errs = ctx.PrepareBuildActions(config)
+	if len(errs) > 0 {
+		android.FailIfNoMatchingErrors(t, pattern, errs)
+		return
+	}
+
+	t.Fatalf("missing expected error %q (0 errors are returned)", pattern)
+}
+
 func testApex(t *testing.T, bp string) *android.TestContext {
+	ctx, config := testApexContext(t, bp)
+	_, errs := ctx.ParseFileList(".", []string{"Android.bp"})
+	android.FailIfErrored(t, errs)
+	_, errs = ctx.PrepareBuildActions(config)
+	android.FailIfErrored(t, errs)
+	return ctx
+}
+
+func testApexContext(t *testing.T, bp string) (*android.TestContext, android.Config) {
 	config := android.TestArchConfig(buildDir, nil)
 	config.TestProductVariables.DeviceVndkVersion = proptools.StringPtr("current")
 	config.TestProductVariables.DefaultAppCertificate = proptools.StringPtr("vendor/foo/devkeys/test")
@@ -48,6 +73,7 @@
 	ctx.PostDepsMutators(func(ctx android.RegisterMutatorsContext) {
 		ctx.TopDown("apex_deps", apexDepsMutator)
 		ctx.BottomUp("apex", apexMutator)
+		ctx.BottomUp("apex_uses", apexUsesMutator)
 		ctx.TopDown("prebuilt_select", android.PrebuiltSelectModuleMutator).Parallel()
 		ctx.BottomUp("prebuilt_postdeps", android.PrebuiltPostDepsMutator).Parallel()
 	})
@@ -168,8 +194,10 @@
 		"system/sepolicy/apex/myapex-file_contexts":         nil,
 		"system/sepolicy/apex/myapex_keytest-file_contexts": nil,
 		"system/sepolicy/apex/otherapex-file_contexts":      nil,
+		"system/sepolicy/apex/commonapex-file_contexts":     nil,
 		"mylib.cpp":                            nil,
 		"mytest.cpp":                           nil,
+		"mylib_common.cpp":                     nil,
 		"myprebuilt":                           nil,
 		"my_include":                           nil,
 		"vendor/foo/devkeys/test.x509.pem":     nil,
@@ -188,12 +216,8 @@
 		"myapex-arm.apex":                      nil,
 		"frameworks/base/api/current.txt":      nil,
 	})
-	_, errs := ctx.ParseFileList(".", []string{"Android.bp"})
-	android.FailIfErrored(t, errs)
-	_, errs = ctx.PrepareBuildActions(config)
-	android.FailIfErrored(t, errs)
 
-	return ctx
+	return ctx, config
 }
 
 func setUp() {
@@ -210,6 +234,7 @@
 
 // ensure that 'result' contains 'expected'
 func ensureContains(t *testing.T, result string, expected string) {
+	t.Helper()
 	if !strings.Contains(result, expected) {
 		t.Errorf("%q is not found in %q", expected, result)
 	}
@@ -217,18 +242,21 @@
 
 // ensures that 'result' does not contain 'notExpected'
 func ensureNotContains(t *testing.T, result string, notExpected string) {
+	t.Helper()
 	if strings.Contains(result, notExpected) {
 		t.Errorf("%q is found in %q", notExpected, result)
 	}
 }
 
 func ensureListContains(t *testing.T, result []string, expected string) {
+	t.Helper()
 	if !android.InList(expected, result) {
 		t.Errorf("%q is not found in %v", expected, result)
 	}
 }
 
 func ensureListNotContains(t *testing.T, result []string, notExpected string) {
+	t.Helper()
 	if android.InList(notExpected, result) {
 		t.Errorf("%q is found in %v", notExpected, result)
 	}
@@ -789,6 +817,30 @@
 	ensureNotContains(t, inputsString, "android_arm64_armv8-a_core_shared_myapex/mylib2.so")
 }
 
+func TestUseVendorFailsIfNotVendorAvailable(t *testing.T) {
+	testApexError(t, `dependency "mylib" of "myapex" missing variant:\n.*image:vendor`, `
+		apex {
+			name: "myapex",
+			key: "myapex.key",
+			native_shared_libs: ["mylib"],
+			use_vendor: true,
+		}
+
+		apex_key {
+			name: "myapex.key",
+			public_key: "testkey.avbpubkey",
+			private_key: "testkey.pem",
+		}
+
+		cc_library {
+			name: "mylib",
+			srcs: ["mylib.cpp"],
+			system_shared_libs: [],
+			stl: "none",
+		}
+	`)
+}
+
 func TestStaticLinking(t *testing.T) {
 	ctx := testApex(t, `
 		apex {
@@ -1321,6 +1373,122 @@
 	ensureContains(t, copyCmds, "image.apex/bin/test/mytest")
 }
 
+func TestApexUsesOtherApex(t *testing.T) {
+	ctx := testApex(t, `
+		apex {
+			name: "myapex",
+			key: "myapex.key",
+			native_shared_libs: ["mylib"],
+			uses: ["commonapex"],
+		}
+
+		apex {
+			name: "commonapex",
+			key: "myapex.key",
+			native_shared_libs: ["libcommon"],
+			provide_cpp_shared_libs: true,
+		}
+
+		apex_key {
+			name: "myapex.key",
+			public_key: "testkey.avbpubkey",
+			private_key: "testkey.pem",
+		}
+
+		cc_library {
+			name: "mylib",
+			srcs: ["mylib.cpp"],
+			shared_libs: ["libcommon"],
+			system_shared_libs: [],
+			stl: "none",
+		}
+
+		cc_library {
+			name: "libcommon",
+			srcs: ["mylib_common.cpp"],
+			system_shared_libs: [],
+			stl: "none",
+		}
+	`)
+
+	module1 := ctx.ModuleForTests("myapex", "android_common_myapex")
+	apexRule1 := module1.Rule("apexRule")
+	copyCmds1 := apexRule1.Args["copy_commands"]
+
+	module2 := ctx.ModuleForTests("commonapex", "android_common_commonapex")
+	apexRule2 := module2.Rule("apexRule")
+	copyCmds2 := apexRule2.Args["copy_commands"]
+
+	ensureListContains(t, ctx.ModuleVariantsForTests("mylib"), "android_arm64_armv8-a_core_shared_myapex")
+	ensureListContains(t, ctx.ModuleVariantsForTests("libcommon"), "android_arm64_armv8-a_core_shared_commonapex")
+	ensureContains(t, copyCmds1, "image.apex/lib64/mylib.so")
+	ensureContains(t, copyCmds2, "image.apex/lib64/libcommon.so")
+	ensureNotContains(t, copyCmds1, "image.apex/lib64/libcommon.so")
+}
+
+func TestApexUsesFailsIfNotProvided(t *testing.T) {
+	testApexError(t, `uses: "commonapex" does not provide native_shared_libs`, `
+		apex {
+			name: "myapex",
+			key: "myapex.key",
+			uses: ["commonapex"],
+		}
+
+		apex {
+			name: "commonapex",
+			key: "myapex.key",
+		}
+
+		apex_key {
+			name: "myapex.key",
+			public_key: "testkey.avbpubkey",
+			private_key: "testkey.pem",
+		}
+	`)
+	testApexError(t, `uses: "commonapex" is not a provider`, `
+		apex {
+			name: "myapex",
+			key: "myapex.key",
+			uses: ["commonapex"],
+		}
+
+		cc_library {
+			name: "commonapex",
+			system_shared_libs: [],
+			stl: "none",
+		}
+
+		apex_key {
+			name: "myapex.key",
+			public_key: "testkey.avbpubkey",
+			private_key: "testkey.pem",
+		}
+	`)
+}
+
+func TestApexUsesFailsIfUseVenderMismatch(t *testing.T) {
+	testApexError(t, `use_vendor: "commonapex" has different value of use_vendor`, `
+		apex {
+			name: "myapex",
+			key: "myapex.key",
+			use_vendor: true,
+			uses: ["commonapex"],
+		}
+
+		apex {
+			name: "commonapex",
+			key: "myapex.key",
+			provide_cpp_shared_libs: true,
+		}
+
+		apex_key {
+			name: "myapex.key",
+			public_key: "testkey.avbpubkey",
+			private_key: "testkey.pem",
+		}
+	`)
+}
+
 func TestMain(m *testing.M) {
 	run := func() int {
 		setUp()
diff --git a/cc/binary.go b/cc/binary.go
index 1757f1c..149a92e 100644
--- a/cc/binary.go
+++ b/cc/binary.go
@@ -444,7 +444,8 @@
 	// Bionic binaries (e.g. linker) is installed to the bootstrap subdirectory.
 	// The original path becomes a symlink to the corresponding file in the
 	// runtime APEX.
-	if installToBootstrap(ctx.baseModuleName(), ctx.Config()) && ctx.Arch().Native && ctx.apexName() == "" && !ctx.inRecovery() {
+	translatedArch := ctx.Target().NativeBridge == android.NativeBridgeEnabled || !ctx.Arch().Native
+	if installToBootstrap(ctx.baseModuleName(), ctx.Config()) && !translatedArch && ctx.apexName() == "" && !ctx.inRecovery() {
 		if ctx.Device() && isBionic(ctx.baseModuleName()) {
 			binary.installSymlinkToRuntimeApex(ctx, file)
 		}
diff --git a/cc/library.go b/cc/library.go
index 6ac0c39..cb31979 100644
--- a/cc/library.go
+++ b/cc/library.go
@@ -952,7 +952,8 @@
 			// Bionic libraries (e.g. libc.so) is installed to the bootstrap subdirectory.
 			// The original path becomes a symlink to the corresponding file in the
 			// runtime APEX.
-			if installToBootstrap(ctx.baseModuleName(), ctx.Config()) && !library.buildStubs() && ctx.Arch().Native && !ctx.inRecovery() {
+			translatedArch := ctx.Target().NativeBridge == android.NativeBridgeEnabled || !ctx.Arch().Native
+			if installToBootstrap(ctx.baseModuleName(), ctx.Config()) && !library.buildStubs() && !translatedArch && !ctx.inRecovery() {
 				if ctx.Device() && isBionic(ctx.baseModuleName()) {
 					library.installSymlinkToRuntimeApex(ctx, file)
 				}
diff --git a/cc/sanitize.go b/cc/sanitize.go
index 0eb9a74..c59f53a 100644
--- a/cc/sanitize.go
+++ b/cc/sanitize.go
@@ -445,7 +445,6 @@
 			// libraries needed with -fsanitize=address. http://b/18650275 (WAI)
 			flags.LdFlags = append(flags.LdFlags, "-Wl,--no-as-needed")
 		} else {
-			flags.CFlags = append(flags.CFlags, "-mllvm", "-asan-globals=0")
 			if ctx.bootstrap() {
 				flags.DynamicLinker = "/system/bin/bootstrap/linker_asan"
 			} else {
diff --git a/java/app.go b/java/app.go
index e12b56c..3442658 100644
--- a/java/app.go
+++ b/java/app.go
@@ -30,8 +30,7 @@
 	"android/soong/tradefed"
 )
 
-var supportedDpis = [...]string{"Ldpi", "Mdpi", "Hdpi", "Xhdpi", "Xxhdpi", "Xxxhdpi"}
-var dpiVariantsStruct reflect.Type
+var supportedDpis = []string{"ldpi", "mdpi", "hdpi", "xhdpi", "xxhdpi", "xxxhdpi"}
 
 func init() {
 	android.RegisterModuleType("android_app", AndroidAppFactory)
@@ -40,22 +39,6 @@
 	android.RegisterModuleType("android_app_certificate", AndroidAppCertificateFactory)
 	android.RegisterModuleType("override_android_app", OverrideAndroidAppModuleFactory)
 	android.RegisterModuleType("android_app_import", AndroidAppImportFactory)
-
-	// Dynamically construct a struct for the dpi_variants property in android_app_import.
-	perDpiStruct := reflect.StructOf([]reflect.StructField{
-		{
-			Name: "Apk",
-			Type: reflect.TypeOf((*string)(nil)),
-		},
-	})
-	dpiVariantsFields := make([]reflect.StructField, len(supportedDpis))
-	for i, dpi := range supportedDpis {
-		dpiVariantsFields[i] = reflect.StructField{
-			Name: string(dpi),
-			Type: perDpiStruct,
-		}
-	}
-	dpiVariantsStruct = reflect.StructOf(dpiVariantsFields)
 }
 
 // AndroidManifest.xml merging
@@ -744,7 +727,8 @@
 	android.DefaultableModuleBase
 	prebuilt android.Prebuilt
 
-	properties AndroidAppImportProperties
+	properties  AndroidAppImportProperties
+	dpiVariants interface{}
 
 	outputFile  android.Path
 	certificate *Certificate
@@ -756,27 +740,7 @@
 
 type AndroidAppImportProperties struct {
 	// A prebuilt apk to import
-	Apk string
-
-	// Per-DPI settings. This property makes it possible to specify a different source apk path for
-	// each DPI.
-	//
-	// Example:
-	//
-	//     android_app_import {
-	//         name: "example_import",
-	//         apk: "prebuilts/example.apk",
-	//         dpi_variants: {
-	//             mdpi: {
-	//                 apk: "prebuilts/example_mdpi.apk",
-	//             },
-	//             xhdpi: {
-	//                 apk: "prebuilts/example_xhdpi.apk",
-	//             },
-	//         },
-	//         certificate: "PRESIGNED",
-	//     }
-	Dpi_variants interface{}
+	Apk *string
 
 	// The name of a certificate in the default certificate directory, blank to use the default
 	// product certificate, or an android_app_certificate module name in the form ":module".
@@ -799,39 +763,43 @@
 	Overrides []string
 }
 
-func getApkPathForDpi(dpiVariantsValue reflect.Value, dpi string) string {
-	dpiField := dpiVariantsValue.FieldByName(proptools.FieldNameForProperty(dpi))
-	if !dpiField.IsValid() {
-		return ""
+// Chooses a source APK path to use based on the module and product specs.
+func (a *AndroidAppImport) updateSrcApkPath(ctx android.LoadHookContext) {
+	config := ctx.Config()
+
+	dpiProps := reflect.ValueOf(a.dpiVariants).Elem().FieldByName("Dpi_variants")
+	// Try DPI variant matches in the reverse-priority order so that the highest priority match
+	// overwrites everything else.
+	// TODO(jungjw): Can we optimize this by making it priority order?
+	for i := len(config.ProductAAPTPrebuiltDPI()) - 1; i >= 0; i-- {
+		dpi := config.ProductAAPTPrebuiltDPI()[i]
+		if inList(dpi, supportedDpis) {
+			MergePropertiesFromVariant(ctx, &a.properties, dpiProps, dpi, "dpi_variants")
+		}
 	}
-	apkValue := dpiField.FieldByName("Apk").Elem()
-	if apkValue.IsValid() {
-		return apkValue.String()
+	if config.ProductAAPTPreferredConfig() != "" {
+		dpi := config.ProductAAPTPreferredConfig()
+		if inList(dpi, supportedDpis) {
+			MergePropertiesFromVariant(ctx, &a.properties, dpiProps, dpi, "dpi_variants")
+		}
 	}
-	return ""
 }
 
-// Chooses a source APK path to use based on the module's per-DPI settings and the product config.
-func (a *AndroidAppImport) getSrcApkPath(ctx android.ModuleContext) string {
-	config := ctx.Config()
-	dpiVariantsValue := reflect.ValueOf(a.properties.Dpi_variants).Elem()
-	if !dpiVariantsValue.IsValid() {
-		return a.properties.Apk
-	}
-	// Match PRODUCT_AAPT_PREF_CONFIG first and then PRODUCT_AAPT_PREBUILT_DPI.
-	if config.ProductAAPTPreferredConfig() != "" {
-		if apk := getApkPathForDpi(dpiVariantsValue, config.ProductAAPTPreferredConfig()); apk != "" {
-			return apk
-		}
-	}
-	for _, dpi := range config.ProductAAPTPrebuiltDPI() {
-		if apk := getApkPathForDpi(dpiVariantsValue, dpi); apk != "" {
-			return apk
-		}
+func MergePropertiesFromVariant(ctx android.BaseModuleContext,
+	dst interface{}, variantGroup reflect.Value, variant, variantGroupPath string) {
+	src := variantGroup.FieldByName(proptools.FieldNameForProperty(variant))
+	if !src.IsValid() {
+		ctx.ModuleErrorf("field %q does not exist", variantGroupPath+"."+variant)
 	}
 
-	// No match. Use the generic one.
-	return a.properties.Apk
+	err := proptools.ExtendMatchingProperties([]interface{}{dst}, src.Interface(), nil, proptools.OrderAppend)
+	if err != nil {
+		if propertyErr, ok := err.(*proptools.ExtendPropertyError); ok {
+			ctx.PropertyErrorf(propertyErr.Property, "%s", propertyErr.Err.Error())
+		} else {
+			panic(err)
+		}
+	}
 }
 
 func (a *AndroidAppImport) DepsMutator(ctx android.BottomUpMutatorContext) {
@@ -896,8 +864,7 @@
 	// TODO: LOCAL_EXTRACT_APK/LOCAL_EXTRACT_DPI_APK
 	// TODO: LOCAL_PACKAGE_SPLITS
 
-	var srcApk android.Path
-	srcApk = android.PathForModuleSrc(ctx, a.getSrcApkPath(ctx))
+	srcApk := a.prebuilt.SingleSourcePath(ctx)
 
 	if a.usesLibrary.enforceUsesLibraries() {
 		srcApk = a.usesLibrary.verifyUsesLibrariesAPK(ctx, srcApk)
@@ -959,16 +926,56 @@
 	return a.prebuilt.Name(a.ModuleBase.Name())
 }
 
+// Populates dpi_variants property and its fields at creation time.
+func (a *AndroidAppImport) addDpiVariants() {
+	// TODO(jungjw): Do we want to do some filtering here?
+	props := reflect.ValueOf(&a.properties).Type()
+
+	dpiFields := make([]reflect.StructField, len(supportedDpis))
+	for i, dpi := range supportedDpis {
+		dpiFields[i] = reflect.StructField{
+			Name: proptools.FieldNameForProperty(dpi),
+			Type: props,
+		}
+	}
+	dpiStruct := reflect.StructOf(dpiFields)
+	a.dpiVariants = reflect.New(reflect.StructOf([]reflect.StructField{
+		{
+			Name: "Dpi_variants",
+			Type: dpiStruct,
+		},
+	})).Interface()
+	a.AddProperties(a.dpiVariants)
+}
+
 // android_app_import imports a prebuilt apk with additional processing specified in the module.
+// DPI-specific apk source files can be specified using dpi_variants. Example:
+//
+//     android_app_import {
+//         name: "example_import",
+//         apk: "prebuilts/example.apk",
+//         dpi_variants: {
+//             mdpi: {
+//                 apk: "prebuilts/example_mdpi.apk",
+//             },
+//             xhdpi: {
+//                 apk: "prebuilts/example_xhdpi.apk",
+//             },
+//         },
+//         certificate: "PRESIGNED",
+//     }
 func AndroidAppImportFactory() android.Module {
 	module := &AndroidAppImport{}
-	module.properties.Dpi_variants = reflect.New(dpiVariantsStruct).Interface()
 	module.AddProperties(&module.properties)
 	module.AddProperties(&module.dexpreoptProperties)
 	module.AddProperties(&module.usesLibrary.usesLibraryProperties)
+	module.addDpiVariants()
+	android.AddLoadHook(module, func(ctx android.LoadHookContext) {
+		module.updateSrcApkPath(ctx)
+	})
 
 	InitJavaModule(module, android.DeviceSupported)
-	android.InitSingleSourcePrebuiltModule(module, &module.properties.Apk)
+	android.InitSingleSourcePrebuiltModule(module, &module.properties, "Apk")
 
 	return module
 }
diff --git a/java/app_test.go b/java/app_test.go
index 721dd4d..f08969d 100644
--- a/java/app_test.go
+++ b/java/app_test.go
@@ -1138,7 +1138,7 @@
 		{
 			name:                "AAPTPreferredConfig matches",
 			aaptPreferredConfig: proptools.StringPtr("xhdpi"),
-			aaptPrebuiltDPI:     []string{"xxhdpi", "lhdpi"},
+			aaptPrebuiltDPI:     []string{"xxhdpi", "ldpi"},
 			expected:            "prebuilts/apk/app_xhdpi.apk",
 		},
 		{
diff --git a/java/config/config.go b/java/config/config.go
index 6ade649..d017ae6 100644
--- a/java/config/config.go
+++ b/java/config/config.go
@@ -52,7 +52,7 @@
 
 	pctx.StaticVariable("JavacHeapSize", "2048M")
 	pctx.StaticVariable("JavacHeapFlags", "-J-Xmx${JavacHeapSize}")
-	pctx.StaticVariable("DexFlags", "-JXX:+TieredCompilation -JXX:TieredStopAtLevel=1")
+	pctx.StaticVariable("DexFlags", "-JXX:OnError='cat hs_err_pid%p.log' -JXX:CICompilerCount=6 -JXX:+UseDynamicNumberOfGCThreads")
 
 	pctx.StaticVariable("CommonJdkFlags", strings.Join([]string{
 		`-Xmaxerrs 9999999`,
diff --git a/java/sdk_library.go b/java/sdk_library.go
index b4a3f29..1182b96 100644
--- a/java/sdk_library.go
+++ b/java/sdk_library.go
@@ -63,12 +63,6 @@
 	javaSdkLibrariesLock sync.Mutex
 )
 
-// java_sdk_library is to make a Java library that implements optional platform APIs to apps.
-// It is actually a wrapper of several modules: 1) stubs library that clients are linked against
-// to, 2) droiddoc module that internally generates API stubs source files, 3) the real runtime
-// shared library that implements the APIs, and 4) XML file for adding the runtime lib to the
-// classpath at runtime if requested via <uses-library>.
-//
 // TODO: these are big features that are currently missing
 // 1) disallowing linking to the runtime shared lib
 // 2) HTML generation
@@ -746,6 +740,11 @@
 	module.Library.Module.deviceProperties.IsSDKLibrary = true
 }
 
+// java_sdk_library is a special Java library that provides optional platform APIs to apps.
+// In practice, it can be viewed as a combination of several modules: 1) stubs library that clients
+// are linked against to, 2) droiddoc module that internally generates API stubs source files,
+// 3) the real runtime shared library that implements the APIs, and 4) XML file for adding
+// the runtime lib to the classpath at runtime if requested via <uses-library>.
 func SdkLibraryFactory() android.Module {
 	module := &SdkLibrary{}
 	module.InitSdkLibraryProperties()
@@ -787,6 +786,7 @@
 
 var _ SdkLibraryDependency = (*sdkLibraryImport)(nil)
 
+// java_sdk_library_import imports a prebuilt java_sdk_library.
 func sdkLibraryImportFactory() android.Module {
 	module := &sdkLibraryImport{}
 
diff --git a/scripts/system-clang-format b/scripts/system-clang-format
index 14abd93..a7614d2 100644
--- a/scripts/system-clang-format
+++ b/scripts/system-clang-format
@@ -1,4 +1,5 @@
 BasedOnStyle: Google
+Standard: Cpp11
 AccessModifierOffset: -2
 AllowShortFunctionsOnASingleLine: Inline
 ColumnLimit: 100
diff --git a/scripts/system-clang-format-2 b/scripts/system-clang-format-2
index e28b379..a4e23f8 100644
--- a/scripts/system-clang-format-2
+++ b/scripts/system-clang-format-2
@@ -1,4 +1,5 @@
 BasedOnStyle: Google
+Standard: Cpp11
 AllowShortFunctionsOnASingleLine: Inline
 ColumnLimit: 100
 CommentPragmas: NOLINT:.*