Fix race conditions in window snapshot code.

cc/test/layer_tree_test.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/test/layer_tree_test.h"
 
 #include "base/command_line.h"
 #include "cc/animation/animation.h"
 #include "cc/animation/animation_registrar.h"
 #include "cc/animation/layer_animation_controller.h"
@@ skipping 401 matching lines @@
 }
 
 void LayerTreeTest::PostSetVisibleToMainThread(bool visible) {
   proxy()->MainThreadTaskRunner()->PostTask(
       FROM_HERE,
       base::Bind(&LayerTreeTest::DispatchSetVisible,
                  main_thread_weak_ptr_,
                  visible));
 }
 
+void LayerTreeTest::PostSetNextCommitForcesRedrawToMainThread() {
+  proxy()->MainThreadTaskRunner()->PostTask(
+      FROM_HERE,
+      base::Bind(&LayerTreeTest::DispatchSetNextCommitForcesRedraw,
+                 main_thread_weak_ptr_));
+}
+
 void LayerTreeTest::DoBeginTest() {
   client_ = LayerTreeHostClientForTesting::Create(this);
 
   DCHECK(!impl_thread_ || impl_thread_->message_loop_proxy().get());
   layer_tree_host_ = LayerTreeHostForTesting::Create(
       this,
       client_.get(),
       settings_,
       impl_thread_ ? impl_thread_->message_loop_proxy() : NULL);
   ASSERT_TRUE(layer_tree_host_);
@@ skipping 124 matching lines @@
     return;
 
   layer_tree_host_->SetVisible(visible);
 
   // If the LTH is being made visible and a previous ScheduleComposite() was
   // deferred because the LTH was not visible, re-schedule the composite now.
   if (layer_tree_host_->visible() && schedule_when_set_visible_true_)
     ScheduleComposite();
 }
 
+void LayerTreeTest::DispatchSetNextCommitForcesRedraw() {
+  DCHECK(!proxy() || proxy()->IsMainThread());
+
+  if (layer_tree_host_)
+    layer_tree_host_->SetNextCommitForcesRedraw();
+}
+
 void LayerTreeTest::DispatchComposite() {
   scheduled_ = false;
 
   if (!layer_tree_host_)
     return;
 
   // If the LTH is not visible, defer the composite until the LTH is made
   // visible.
   if (!layer_tree_host_->visible()) {
     schedule_when_set_visible_true_ = true;
@@ skipping 78 matching lines @@
 
 scoped_refptr<cc::ContextProvider> LayerTreeTest::
     OffscreenContextProviderForCompositorThread() {
   if (!compositor_thread_contexts_.get() ||
       compositor_thread_contexts_->DestroyedOnMainThread())
     compositor_thread_contexts_ = TestContextProvider::Create();
   return compositor_thread_contexts_;
 }
 
 }  // namespace cc