Revert^4 "add crate_root property to rust modules"

9c64274b275a00d7753bbe1a15945652521b2044

Change-Id: I1c4dad76842cebf18cd82e04e435910f09038d07
diff --git a/rust/library.go b/rust/library.go
index 0357086..f4a2b54 100644
--- a/rust/library.go
+++ b/rust/library.go
@@ -489,7 +489,7 @@
 	var outputFile android.ModuleOutPath
 	var ret buildOutput
 	var fileName string
-	srcPath := library.srcPath(ctx, deps)
+	crateRootPath := library.crateRootPath(ctx, deps)
 
 	if library.sourceProvider != nil {
 		deps.srcProviderFiles = append(deps.srcProviderFiles, library.sourceProvider.Srcs()...)
@@ -536,13 +536,13 @@
 
 	// Call the appropriate builder for this library type
 	if library.rlib() {
-		ret.kytheFile = TransformSrctoRlib(ctx, srcPath, deps, flags, outputFile).kytheFile
+		ret.kytheFile = TransformSrctoRlib(ctx, crateRootPath, deps, flags, outputFile).kytheFile
 	} else if library.dylib() {
-		ret.kytheFile = TransformSrctoDylib(ctx, srcPath, deps, flags, outputFile).kytheFile
+		ret.kytheFile = TransformSrctoDylib(ctx, crateRootPath, deps, flags, outputFile).kytheFile
 	} else if library.static() {
-		ret.kytheFile = TransformSrctoStatic(ctx, srcPath, deps, flags, outputFile).kytheFile
+		ret.kytheFile = TransformSrctoStatic(ctx, crateRootPath, deps, flags, outputFile).kytheFile
 	} else if library.shared() {
-		ret.kytheFile = TransformSrctoShared(ctx, srcPath, deps, flags, outputFile).kytheFile
+		ret.kytheFile = TransformSrctoShared(ctx, crateRootPath, deps, flags, outputFile).kytheFile
 	}
 
 	if library.rlib() || library.dylib() {
@@ -585,13 +585,15 @@
 	return ret
 }
 
-func (library *libraryDecorator) srcPath(ctx ModuleContext, _ PathDeps) android.Path {
+func (library *libraryDecorator) crateRootPath(ctx ModuleContext, _ PathDeps) android.Path {
 	if library.sourceProvider != nil {
 		// Assume the first source from the source provider is the library entry point.
 		return library.sourceProvider.Srcs()[0]
-	} else {
+	} else if library.baseCompiler.Properties.Crate_root == nil {
 		path, _ := srcPathFromModuleSrcs(ctx, library.baseCompiler.Properties.Srcs)
 		return path
+	} else {
+		return android.PathForModuleSrc(ctx, *library.baseCompiler.Properties.Crate_root)
 	}
 }
 
@@ -606,7 +608,7 @@
 		return android.OptionalPath{}
 	}
 
-	return android.OptionalPathForPath(Rustdoc(ctx, library.srcPath(ctx, deps),
+	return android.OptionalPathForPath(Rustdoc(ctx, library.crateRootPath(ctx, deps),
 		deps, flags))
 }