Shouldn't access LayerTreeTest::layer_tree_host on impl thread

cc/trees/single_thread_proxy.cc

 // Copyright 2011 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 "cc/trees/single_thread_proxy.h"
 
 #include "base/auto_reset.h"
 #include "base/debug/trace_event.h"
 #include "cc/base/thread.h"
 #include "cc/output/context_provider.h"
@@ skipping 79 matching lines @@
   DCHECK(Proxy::IsMainThread());
   return layer_tree_host_impl_;
 }
 
 void SingleThreadProxy::SetLayerTreeHostClientReady() {
   // Scheduling is controlled by the embedder in the single thread case, so
   // nothing to do.
 }
 
 void SingleThreadProxy::SetVisible(bool visible) {
-  DebugScopedSetImplThread impl(this);
+  DebugScopedSetImplThreadAndMainThreadBlocked impl(this);
   layer_tree_host_impl_->SetVisible(visible);
 }
 
 void SingleThreadProxy::CreateAndInitializeOutputSurface() {
   TRACE_EVENT0(
       "cc", "SingleThreadProxy::CreateAndInitializeOutputSurface");
   DCHECK(Proxy::IsMainThread());
 
   scoped_ptr<OutputSurface> output_surface = first_output_surface_.Pass();
   if (!output_surface)
@@ skipping 58 matching lines @@
 
 void SingleThreadProxy::SetNeedsAnimate() {
   // Thread-only feature.
   NOTREACHED();
 }
 
 void SingleThreadProxy::DoCommit(scoped_ptr<ResourceUpdateQueue> queue) {
   DCHECK(Proxy::IsMainThread());
   // Commit immediately.
   {
-    DebugScopedSetMainThreadBlocked mainThreadBlocked(this);
-    DebugScopedSetImplThread impl(this);
-
+    DebugScopedSetImplThreadAndMainThreadBlocked impl_with_main_blocked(this);
     RenderingStatsInstrumentation* stats_instrumentation =
         layer_tree_host_->rendering_stats_instrumentation();
     base::TimeTicks start_time = stats_instrumentation->StartRecording();
 
     layer_tree_host_impl_->BeginCommit();
 
     layer_tree_host_->contents_texture_manager()->
         PushTexturePrioritiesToBackings();
     layer_tree_host_->BeginCommitOnImplThread(layer_tree_host_impl_.get());
 
@@ skipping 286 matching lines @@
 
 bool SingleThreadProxy::CommitPendingForTesting() { return false; }
 
 skia::RefPtr<SkPicture> SingleThreadProxy::CapturePicture() {
   // Impl-side painting only.
   NOTREACHED();
   return skia::RefPtr<SkPicture>();
 }
 
 }  // namespace cc