Log information for Mixed Builds modules.
Test: Output matches expected. https://paste.googleplex.com/5913495636803584?raw
Performance evaluated: https://docs.google.com/spreadsheets/d/1X7eOVBKEZUwUWl5i8CDfBo9yUeZrDPXWi2JYO4BEZt4/edit?resourcekey=0-co8crIFW9dpiedhCMkhAgw#gid=0

Change-Id: I88780c7cc52a189a72216c5e2e499c96574b3731
diff --git a/android/bazel.go b/android/bazel.go
index 4ef8d78..67002ec 100644
--- a/android/bazel.go
+++ b/android/bazel.go
@@ -338,9 +338,19 @@
 	return false
 }
 
-// MixedBuildsEnabled checks that a module is ready to be replaced by a
+// MixedBuildsEnabled returns true if a module is ready to be replaced by a
+// converted or handcrafted Bazel target. As a side effect, calling this
+// method will also log whether this module is mixed build enabled for
+// metrics reporting.
+func MixedBuildsEnabled(ctx ModuleContext) bool {
+	mixedBuildEnabled := mixedBuildPossible(ctx)
+	ctx.Config().LogMixedBuild(ctx, mixedBuildEnabled)
+	return mixedBuildEnabled
+}
+
+// mixedBuildPossible returns true if a module is ready to be replaced by a
 // converted or handcrafted Bazel target.
-func (b *BazelModuleBase) MixedBuildsEnabled(ctx ModuleContext) bool {
+func mixedBuildPossible(ctx ModuleContext) bool {
 	if ctx.Os() == Windows {
 		// Windows toolchains are not currently supported.
 		return false
diff --git a/android/config.go b/android/config.go
index ee058e8..d695217 100644
--- a/android/config.go
+++ b/android/config.go
@@ -170,6 +170,10 @@
 	ninjaFileDepsSet sync.Map
 
 	OncePer
+
+	mixedBuildsLock           sync.Mutex
+	mixedBuildEnabledModules  map[string]struct{}
+	mixedBuildDisabledModules map[string]struct{}
 }
 
 type deviceConfig struct {
@@ -375,7 +379,9 @@
 		// passed to PathForSource or PathForModuleSrc.
 		TestAllowNonExistentPaths: true,
 
-		BazelContext: noopBazelContext{},
+		BazelContext:              noopBazelContext{},
+		mixedBuildDisabledModules: make(map[string]struct{}),
+		mixedBuildEnabledModules:  make(map[string]struct{}),
 	}
 	config.deviceConfig = &deviceConfig{
 		config: config,
@@ -466,8 +472,10 @@
 		runGoTests:        runGoTests,
 		multilibConflicts: make(map[ArchType]bool),
 
-		moduleListFile: moduleListFile,
-		fs:             pathtools.NewOsFs(absSrcDir),
+		moduleListFile:            moduleListFile,
+		fs:                        pathtools.NewOsFs(absSrcDir),
+		mixedBuildDisabledModules: make(map[string]struct{}),
+		mixedBuildEnabledModules:  make(map[string]struct{}),
 	}
 
 	config.deviceConfig = &deviceConfig{
@@ -2038,3 +2046,14 @@
 func (c *config) UseHostMusl() bool {
 	return Bool(c.productVariables.HostMusl)
 }
+
+func (c *config) LogMixedBuild(ctx ModuleContext, useBazel bool) {
+	moduleName := ctx.Module().Name()
+	c.mixedBuildsLock.Lock()
+	defer c.mixedBuildsLock.Unlock()
+	if useBazel {
+		c.mixedBuildEnabledModules[moduleName] = struct{}{}
+	} else {
+		c.mixedBuildDisabledModules[moduleName] = struct{}{}
+	}
+}
diff --git a/android/filegroup.go b/android/filegroup.go
index 50356d1..1bf5e07 100644
--- a/android/filegroup.go
+++ b/android/filegroup.go
@@ -115,7 +115,7 @@
 }
 
 func (fg *fileGroup) maybeGenerateBazelBuildActions(ctx ModuleContext) {
-	if !fg.MixedBuildsEnabled(ctx) {
+	if !MixedBuildsEnabled(ctx) {
 		return
 	}
 
diff --git a/android/metrics.go b/android/metrics.go
index 9038bde..1580f82 100644
--- a/android/metrics.go
+++ b/android/metrics.go
@@ -17,6 +17,7 @@
 import (
 	"io/ioutil"
 	"runtime"
+	"sort"
 
 	"github.com/google/blueprint/metrics"
 	"google.golang.org/protobuf/proto"
@@ -78,6 +79,23 @@
 		}
 		metrics.Events = append(metrics.Events, &perfInfo)
 	}
+	mixedBuildsInfo := soong_metrics_proto.MixedBuildsInfo{}
+	mixedBuildEnabledModules := make([]string, 0, len(config.mixedBuildEnabledModules))
+	for module, _ := range config.mixedBuildEnabledModules {
+		mixedBuildEnabledModules = append(mixedBuildEnabledModules, module)
+	}
+
+	mixedBuildDisabledModules := make([]string, 0, len(config.mixedBuildDisabledModules))
+	for module, _ := range config.mixedBuildDisabledModules {
+		mixedBuildDisabledModules = append(mixedBuildDisabledModules, module)
+	}
+	// Sorted for deterministic output.
+	sort.Strings(mixedBuildEnabledModules)
+	sort.Strings(mixedBuildDisabledModules)
+
+	mixedBuildsInfo.MixedBuildEnabledModules = mixedBuildEnabledModules
+	mixedBuildsInfo.MixedBuildDisabledModules = mixedBuildDisabledModules
+	metrics.MixedBuildsInfo = &mixedBuildsInfo
 
 	return metrics
 }