Fix race conditions in window snapshot code.

content/renderer/gpu/render_widget_compositor.cc

 // Copyright (c) 2013 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 "content/renderer/gpu/render_widget_compositor.h"
 
 #include <limits>
 #include <string>
 
 #if defined(OS_ANDROID)
@@ skipping 372 matching lines @@
 }
 
 void RenderWidgetCompositor::NotifyInputThrottledUntilCommit() {
   layer_tree_host_->NotifyInputThrottledUntilCommit();
 }
 
 const cc::Layer* RenderWidgetCompositor::GetRootLayer() const {
   return layer_tree_host_->root_layer();
 }
 
+void RenderWidgetCompositor::SetNeedsForcedRedraw() {
+  layer_tree_host_->SetNextCommitForcesRedraw();
+  setNeedsRedraw();
+}
+
 bool RenderWidgetCompositor::initialize(cc::LayerTreeSettings settings) {
   scoped_refptr<base::MessageLoopProxy> compositor_message_loop_proxy =
       RenderThreadImpl::current()->compositor_message_loop_proxy();
   layer_tree_host_ = cc::LayerTreeHost::Create(this,
                                                settings,
                                                compositor_message_loop_proxy);
   return layer_tree_host_;
 }
 
 void RenderWidgetCompositor::setSurfaceReady() {
@@ skipping 223 matching lines @@
   return RenderThreadImpl::current()->OffscreenContextProviderForMainThread();
 }
 
 scoped_refptr<cc::ContextProvider>
 RenderWidgetCompositor::OffscreenContextProviderForCompositorThread() {
   return RenderThreadImpl::current()->
       OffscreenContextProviderForCompositorThread();
 }
 
 }  // namespace content