Plumb activation time to main

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/memory/ptr_util.h"
 #include "base/profiler/scoped_tracker.h"
 #include "base/trace_event/trace_event.h"
@@ skipping 606 matching lines @@
   task_runner_provider_->MainThreadTaskRunner()->PostTask(
       FROM_HERE, base::Bind(&SingleThreadProxy::BeginMainFrame,
                             weak_factory_.GetWeakPtr(), begin_frame_args));
   layer_tree_host_impl_->DidSendBeginMainFrame();
 }
 
 void SingleThreadProxy::SendBeginMainFrameNotExpectedSoon() {
   layer_tree_host_->BeginMainFrameNotExpectedSoon();
 }
 
+int SingleThreadProxy::SyncTreeSourceFrameNumber() {

[vmpstr, 2017/04/05 19:11:33]

Do we have pending trees in single thread proxy? (I might not know of all the
uses of this :) ).

[brianderson, 2017/04/06 23:43:15]

SingleThreadProxy is only used in the Browser, where we don't need this feature
- so we could just return 0. But it does seem to break the Proxy abstraction to
expose the concept of a SyncTree.

Alternatively, we could pass in the source_frame_number as an argument to
NotifyReadyToActivate. ProxyImpl would pass in the pending tree's number.
SingleThreadProxy would pass in the active_tree's number (since we commit to
active tree).

[panicker, 2017/04/08 00:29:07]

Updated to passing argument to NotifyReadyToActivate and passing pending-tree in
ProxyImpl.
Passing active-tree in SingleThreadProxy triggers a ton of NotifyReadyToActivate
without corresponding BeginMainFrame. 
Are you sure this should be active-tree here? I'll take a closer look.

[panicker, 2017/04/10 22:20:05]

Discussed offline and updated to passing 0 here.

+  if (layer_tree_host_impl_ && layer_tree_host_impl_->pending_tree())
+    return layer_tree_host_impl_->pending_tree()->source_frame_number();
+  else
+    return 0;
+}
+
 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_) {
@@ skipping 151 matching lines @@
 void SingleThreadProxy::DidFinishImplFrame() {
   layer_tree_host_impl_->DidFinishImplFrame();
 #if DCHECK_IS_ON()
   DCHECK(inside_impl_frame_)
       << "DidFinishImplFrame called while not inside an impl frame!";
   inside_impl_frame_ = false;
 #endif
 }
 
 }  // namespace cc