Mus: Fixes rendering of transparent containers.

components/mus/ws/test_utils.cc

Index: components/mus/ws/test_utils.cc
diff --git a/components/mus/ws/test_utils.cc b/components/mus/ws/test_utils.cc
index b2624d32625a47aff75d7f0b97b5b81fc1aeed63..76b0c6734a0b28584ccf10a3747ee2785c4290ed 100644
--- a/components/mus/ws/test_utils.cc
+++ b/components/mus/ws/test_utils.cc
@@ -108,6 +108,22 @@ PlatformDisplay* TestPlatformDisplayFactory::CreatePlatformDisplay() {
   return new TestPlatformDisplay(cursor_id_storage_);
 }
 
+// TestFrameGeneratorDelegate -------------------------------------------------
+
+TestFrameGeneratorDelegate::TestFrameGeneratorDelegate(
+    std::unique_ptr<ServerWindow> root)
+    : root_(std::move(root)) {}
+
+TestFrameGeneratorDelegate::~TestFrameGeneratorDelegate() {}
+
+ServerWindow* TestFrameGeneratorDelegate::GetRootWindow() {
+  return root_.get();
+}
+
+const ViewportMetrics& TestFrameGeneratorDelegate::GetViewportMetrics() {
+  return metrics_;
+}
+
 // WindowTreeTestApi  ---------------------------------------------------------
 
 WindowTreeTestApi::WindowTreeTestApi(WindowTree* tree) : tree_(tree) {}