Add srcjar output for platform_bootclasspath

This output contains all the transitive sources that are contained in
the bootclasspath.

It's currently limited to source-built bootclasspath components. Future
work will make this deal with sdk_library prebuilts.

Bug: 151360309
Test: unit test, as well as manual inspection of platform-bootclasspath
Change-Id: Ie05d8125e19736d8b4b9ebafb70b88a0a40069d5
diff --git a/java/platform_bootclasspath.go b/java/platform_bootclasspath.go
index ade7395..bab0bf6 100644
--- a/java/platform_bootclasspath.go
+++ b/java/platform_bootclasspath.go
@@ -173,6 +173,18 @@
 	allModules = append(allModules, apexModules...)
 	b.configuredModules = allModules
 
+	var transitiveSrcFiles android.Paths
+	for _, module := range allModules {
+		depInfo := ctx.OtherModuleProvider(module, JavaInfoProvider).(JavaInfo)
+		if depInfo.TransitiveSrcFiles != nil {
+			transitiveSrcFiles = append(transitiveSrcFiles, depInfo.TransitiveSrcFiles.ToList()...)
+		}
+	}
+	jarArgs := resourcePathsToJarArgs(transitiveSrcFiles)
+	jarArgs = append(jarArgs, "-srcjar") // Move srcfiles to the right package
+	transitiveSrcJar := android.PathForModuleOut(ctx, ctx.ModuleName()+"-transitive.srcjar")
+	TransformResourcesToJar(ctx, transitiveSrcJar, jarArgs, transitiveSrcFiles)
+
 	// Gather all the fragments dependencies.
 	b.fragments = gatherApexModulePairDepsWithTag(ctx, bootclasspathFragmentDepTag)