Mus: Fixes rendering of transparent containers.

components/mus/ws/test_utils.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/mus/ws/test_utils.h"
 
 #include "base/memory/ptr_util.h"
 #include "cc/output/copy_output_request.h"
 #include "components/mus/surfaces/surfaces_state.h"
 #include "components/mus/ws/display_binding.h"
@@ skipping 89 matching lines @@
 TestPlatformDisplayFactory::TestPlatformDisplayFactory(
     int32_t* cursor_id_storage)
     : cursor_id_storage_(cursor_id_storage) {}
 
 TestPlatformDisplayFactory::~TestPlatformDisplayFactory() {}
 
 PlatformDisplay* TestPlatformDisplayFactory::CreatePlatformDisplay() {
   return new TestPlatformDisplay(cursor_id_storage_);
 }
 
+// TestPlatformDisplayDelegate -------------------------------------------------
+
+TestPlatformDisplayDelegate::TestPlatformDisplayDelegate(
+    std::unique_ptr<ServerWindow> root)
+    : root_(std::move(root)) {}
+
+TestPlatformDisplayDelegate::~TestPlatformDisplayDelegate() {}
+
+ServerWindow* TestPlatformDisplayDelegate::GetRootWindow() {
+  return root_.get();
+}
+
 // WindowTreeTestApi  ---------------------------------------------------------
 
 WindowTreeTestApi::WindowTreeTestApi(WindowTree* tree) : tree_(tree) {}
 WindowTreeTestApi::~WindowTreeTestApi() {}
 
 void WindowTreeTestApi::SetEventObserver(mojom::EventMatcherPtr matcher,
                                          uint32_t event_observer_id) {
   tree_->SetEventObserver(std::move(matcher), event_observer_id);
 }
 
@@ skipping 363 matching lines @@
     return nullptr;
   if (!tree->AddWindow(parent_client_id, client_window_id))
     return nullptr;
   *client_id = client_window_id;
   return tree->GetWindowByClientId(client_window_id);
 }
 
 }  // namespace test
 }  // namespace ws
 }  // namespace mus