cc: Unify context losing machinery

cc/layer_tree_host_impl.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/layer_tree_host_impl.h"
 
 #include <algorithm>
 
 #include "base/basictypes.h"
 #include "base/debug/trace_event.h"
@@ skipping 933 matching lines @@
 }
 
 void LayerTreeHostImpl::finishAllRendering()
 {
     if (m_renderer)
         m_renderer->finish();
 }
 
 bool LayerTreeHostImpl::isContextLost()
 {
+    DCHECK(m_proxy->isImplThread());
     return m_renderer && m_renderer->isContextLost();
 }
 
 const RendererCapabilities& LayerTreeHostImpl::rendererCapabilities() const
 {
     return m_renderer->capabilities();
 }
 
 bool LayerTreeHostImpl::swapBuffers()
 {
@@ skipping 793 matching lines @@
     ScrollbarAnimationController* scrollbarController = layer->scrollbarAnimationController();
     double monotonicTime = (time - base::TimeTicks()).InSecondsF();
     if (scrollbarController && scrollbarController->animate(monotonicTime))
         m_client->setNeedsRedrawOnImplThread();
 
     for (size_t i = 0; i < layer->children().size(); ++i)
         animateScrollbarsRecursive(layer->children()[i], time);
 }
 
 }  // namespace cc