Change classpath for droiddoc

When the module type is SdkLibraryDependency, the classpath has been
gotten from headerJar
Becuase droiddoc uses src files when it builds, we should change to use
ImplementationJars instead of headerJar.

Bug: 77577799
Test: make -j

Change-Id: I1a072be69d7edff5636ea80af700be7796c3b0fc
diff --git a/java/sdk_library.go b/java/sdk_library.go
index e65af65..3bac8f6 100644
--- a/java/sdk_library.go
+++ b/java/sdk_library.go
@@ -129,6 +129,11 @@
 	systemApiStubsPath android.Paths
 	testApiStubsPath   android.Paths
 	implLibPath        android.Paths
+
+	publicApiStubsImplPath android.Paths
+	systemApiStubsImplPath android.Paths
+	testApiStubsImplPath   android.Paths
+	implLibImplPath        android.Paths
 }
 
 func (module *sdkLibrary) DepsMutator(ctx android.BottomUpMutatorContext) {
@@ -151,12 +156,16 @@
 			switch tag {
 			case publicApiStubsTag:
 				module.publicApiStubsPath = lib.HeaderJars()
+				module.publicApiStubsImplPath = lib.ImplementationJars()
 			case systemApiStubsTag:
 				module.systemApiStubsPath = lib.HeaderJars()
+				module.systemApiStubsImplPath = lib.ImplementationJars()
 			case testApiStubsTag:
 				module.testApiStubsPath = lib.HeaderJars()
+				module.testApiStubsImplPath = lib.ImplementationJars()
 			case implLibTag:
 				module.implLibPath = lib.HeaderJars()
+				module.implLibImplPath = lib.ImplementationJars()
 			default:
 				ctx.ModuleErrorf("depends on module %q of unknown tag %q", otherName, tag)
 			}
@@ -557,6 +566,18 @@
 	}
 }
 
+// to satisfy SdkLibraryDependency interface
+func (module *sdkLibrary) ImplementationJars(linkType linkType) android.Paths {
+	// This module is just a wrapper for the stubs.
+	if linkType == javaSystem {
+		return module.systemApiStubsImplPath
+	} else if linkType == javaPlatform {
+		return module.implLibImplPath
+	} else {
+		return module.publicApiStubsImplPath
+	}
+}
+
 func javaSdkLibraries(config android.Config) *[]string {
 	return config.Once("javaSdkLibraries", func() interface{} {
 		return &[]string{}