cc: Add main frame timing info to frame timing tracker.

cc/trees/thread_proxy.cc

Index: cc/trees/thread_proxy.cc
diff --git a/cc/trees/thread_proxy.cc b/cc/trees/thread_proxy.cc
index 8c766f273da9ab0a291133710fed1a7e10b27968..bd5106f2f395639c0fac4b57f448ee54483b982e 100644
--- a/cc/trees/thread_proxy.cc
+++ b/cc/trees/thread_proxy.cc
@@ -691,6 +691,8 @@ void ThreadProxy::ScheduledActionSendBeginMainFrame() {
       impl().layer_tree_host_impl->memory_allocation_priority_cutoff();
   begin_main_frame_state->evicted_ui_resources =
       impl().layer_tree_host_impl->EvictedUIResourcesExist();
+  impl().layer_tree_host_impl->SetBeginMainFrameTime(
+      impl().scheduler->LastBeginImplFrameTime());

[enne (OOO), 2015/03/06 21:27:55]

I still think this is a little weird, in that a lost context on a previous frame
will make the next frame look long, even if that content hadn't even requested a
begin main frame / needs commit.

If the goal is "time to get content on screen", then maybe it makes sense to
time from SetNeedsCommit on the main thread instead?

Sorry for all the confusion here.  I still feel like maybe I'm just missing
something.

   Proxy::MainThreadTaskRunner()->PostTask(
       FROM_HERE,
       base::Bind(&ThreadProxy::BeginMainFrame,
@@ -1394,4 +1396,9 @@ void ThreadProxy::DidCompletePageScaleAnimationOnImplThread() {
                             main_thread_weak_ptr_));
 }
 
+base::TimeTicks ThreadProxy::GetNextBeginImplFrameTimeIfRequested() const {
+  DCHECK(IsImplThread());
+  return impl().scheduler->NextBeginImplFrameTimeIfRequested();
+}
+
 }  // namespace cc