[animations] Adds metrics for jank on selected layer animations

ui/compositor/compositor.cc

 // Copyright (c) 2012 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 "ui/compositor/compositor.h"
 
 #include <stddef.h>
 
 #include <algorithm>
 #include <deque>
@@ skipping 65 matching lines @@
                        ui::ContextFactory* context_factory,
                        ui::ContextFactoryPrivate* context_factory_private,
                        scoped_refptr<base::SingleThreadTaskRunner> task_runner)
     : context_factory_(context_factory),
       context_factory_private_(context_factory_private),
       root_layer_(NULL),
       widget_(gfx::kNullAcceleratedWidget),
 #if defined(USE_AURA)
       window_(nullptr),
 #endif
+      submitted_frame_number_(0),
       widget_valid_(false),
       compositor_frame_sink_requested_(false),
       frame_sink_id_(frame_sink_id),
       task_runner_(task_runner),
       vsync_manager_(new CompositorVSyncManager()),
       device_scale_factor_(0.0f),
       locks_will_time_out_(true),
       compositor_lock_(NULL),
       layer_animator_collection_(this),
       weak_ptr_factory_(this) {
@@ skipping 421 matching lines @@
   for (auto& observer : observer_list_)
     observer.OnCompositingDidCommit(this);
 }
 
 void Compositor::DidReceiveCompositorFrameAck() {
   for (auto& observer : observer_list_)
     observer.OnCompositingEnded(this);
 }
 
 void Compositor::DidSubmitCompositorFrame() {
+  ++submitted_frame_number_;

[reveman, 2017/01/21 15:27:39]

This doesn't mean the frame was displayed. If we submit a bad frame (e.g. one
with lots of overdraw) we might still miss vsync and jank. Should these stats be
hooked up to swap acks instead?

[danakj, 2017/01/23 15:52:05]

Depends if we wanna measure the production of frames from the UI compositor or
the whole stack beyond it.

[varkha, 2017/01/24 00:18:57]

Looking at how WaitForSwap() is implemented I think wiring it to
DidReceiveCompositorFrameAck is the right thing to do if we want to measure what
a user actually sees ("whole stack").

   base::TimeTicks start_time = base::TimeTicks::Now();
   for (auto& observer : observer_list_)
     observer.OnCompositingStarted(this, start_time);
 }
 
 void Compositor::SetOutputIsSecure(bool output_is_secure) {
   if (context_factory_private_)
     context_factory_private_->SetOutputIsSecure(this, output_is_secure);
 }
 
@@ skipping 27 matching lines @@
   for (auto& observer : observer_list_)
     observer.OnCompositingLockStateChanged(this);
 }
 
 void Compositor::CancelCompositorLock() {
   if (compositor_lock_)
     compositor_lock_->CancelLock();
 }
 
 }  // namespace ui