Pipe impl_latency_takes_priority_ to the RenderScheduler.

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/profiler/scoped_tracker.h"
 #include "base/trace_event/trace_event.h"
 #include "cc/debug/benchmark_instrumentation.h"
@@ skipping 592 matching lines @@
   if (layer_tree_host_->output_surface_lost()) {
     RequestNewOutputSurface();
     // RequestNewOutputSurface could have synchronously created an output
     // surface, so check again before returning.
     if (layer_tree_host_->output_surface_lost())
       return;
   }
 
   BeginFrameArgs begin_frame_args(BeginFrameArgs::Create(
       BEGINFRAME_FROM_HERE, frame_begin_time, base::TimeTicks(),
-      BeginFrameArgs::DefaultInterval(), BeginFrameArgs::NORMAL));
+      BeginFrameArgs::DefaultInterval(), BeginFrameArgs::NORMAL,
+      scheduler_on_impl_thread_
+          ? scheduler_on_impl_thread_->MainThreadOnCriticalPath()

[Sami, 2015/06/08 11:47:53]

I think this should default to true when we are using the single threaded
compositor. The compositor can't really do anything before the BeginFrame
completes.

[alex clarke (OOO till 29th), 2015/06/08 16:58:07]

Done.

+          : false));
 
   // Start the impl frame.
   {
     DebugScopedSetImplThread impl(this);
     WillBeginImplFrame(begin_frame_args);
   }
 
   // Run the "main thread" and get it to commit.
   {
 #if DCHECK_IS_ON()
@@ skipping 377 matching lines @@
       << "DidFinishImplFrame called while not inside an impl frame!";
   inside_impl_frame_ = false;
 #endif
 }
 
 void SingleThreadProxy::SendBeginFramesToChildren(const BeginFrameArgs& args) {
   layer_tree_host_->SendBeginFramesToChildren(args);
 }
 
 }  // namespace cc