cc: Track BeginMainFrame more precisely in CompositorTimingHistory.

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 734 matching lines @@
   MainThreadTaskRunner()->PostTask(
       FROM_HERE, base::Bind(&SingleThreadProxy::BeginMainFrame,
                             weak_factory_.GetWeakPtr(), begin_frame_args));
 }
 
 void SingleThreadProxy::SendBeginMainFrameNotExpectedSoon() {
   layer_tree_host_->BeginMainFrameNotExpectedSoon();
 }
 
 void SingleThreadProxy::BeginMainFrame(const BeginFrameArgs& begin_frame_args) {
+  if (scheduler_on_impl_thread_) {
+    scheduler_on_impl_thread_->NotifyBeginMainFrameStarted(
+        base::TimeTicks::Now());
+  }
+
   commit_requested_ = false;
   animate_requested_ = false;
 
   if (defer_commits_) {
     TRACE_EVENT_INSTANT0("cc", "EarlyOut_DeferCommit",
                          TRACE_EVENT_SCOPE_THREAD);
     BeginMainFrameAbortedOnImplThread(
         CommitEarlyOutReason::ABORTED_DEFERRED_COMMIT);
     return;
   }
@@ skipping 33 matching lines @@
   layer_tree_host_->Layout();
 
   // New commits requested inside UpdateLayers should be respected.
   commit_requested_ = false;
 
   layer_tree_host_->UpdateLayers();
 
   // TODO(enne): SingleThreadProxy does not support cancelling commits yet,
   // search for CommitEarlyOutReason::FINISHED_NO_UPDATES inside
   // thread_proxy.cc
-  if (scheduler_on_impl_thread_) {
-    scheduler_on_impl_thread_->NotifyBeginMainFrameStarted();
+  if (scheduler_on_impl_thread_)
     scheduler_on_impl_thread_->NotifyReadyToCommit();
-  }
 }
 
 void SingleThreadProxy::BeginMainFrameAbortedOnImplThread(
     CommitEarlyOutReason reason) {
   DebugScopedSetImplThread impl(this);
   DCHECK(scheduler_on_impl_thread_->CommitPending());
   DCHECK(!layer_tree_host_impl_->pending_tree());
 
   layer_tree_host_impl_->BeginMainFrameAborted(reason);
   scheduler_on_impl_thread_->BeginMainFrameAborted(reason);
@@ skipping 63 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