GPU process clients can perform a "shallow" finish.

cc/trees/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/trees/layer_tree_host_impl.h"
 
 #include <algorithm>
 
 #include "base/basictypes.h"
 #include "base/json/json_writer.h"
@@ skipping 1201 matching lines @@
   for (size_t i = 0; i < frame.will_draw_layers.size(); ++i)
     frame.will_draw_layers[i]->DidDraw(resource_provider_.get());
 
   // Once all layers have been drawn, pending texture uploads should no
   // longer block future uploads.
   if (resource_provider_)
     resource_provider_->MarkPendingUploadsAsNonBlocking();
 }
 
 void LayerTreeHostImpl::FinishAllRendering() {
-  if (renderer_)
-    renderer_->Finish();
+  // Can this be a flush?

[piman, 2013/06/21 02:31:10]

I believe this was needed at some point on some platforms (was it mac?) to avoid
flashing when switching from composited to non-composited.
Mac switched to --force-compositing-mode, so it may not be needed any more.

+  //if (renderer_)
+  //  renderer_->Finish();
 }
 
 bool LayerTreeHostImpl::IsContextLost() {
   DCHECK(proxy_->IsImplThread());
   return renderer_ && renderer_->IsContextLost();
 }
 
 const RendererCapabilities& LayerTreeHostImpl::GetRendererCapabilities() const {
   return renderer_->Capabilities();
 }
@@ skipping 1103 matching lines @@
 }
 
 void LayerTreeHostImpl::SetDebugState(const LayerTreeDebugState& debug_state) {
   if (debug_state_.continuous_painting != debug_state.continuous_painting)
     paint_time_counter_->ClearHistory();
 
   debug_state_ = debug_state;
 }
 
 }  // namespace cc