Hook up ui::Compositor to Display's BeginFrameSource

cc/surfaces/display_scheduler.cc

 // Copyright 2015 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/surfaces/display_scheduler.h"
 
 #include <vector>
 
 #include "base/stl_util.h"
 #include "base/trace_event/trace_event.h"
 #include "cc/output/output_surface.h"
 
 namespace cc {
 
 DisplayScheduler::DisplayScheduler(DisplaySchedulerClient* client,
                                    BeginFrameSource* begin_frame_source,
                                    base::SingleThreadTaskRunner* task_runner,
-                                   int max_pending_swaps)
+                                   int max_pending_swaps,
+                                   const RendererSettings& settings)
     : client_(client),
       begin_frame_source_(begin_frame_source),
       task_runner_(task_runner),
       output_surface_lost_(false),
       root_surface_resources_locked_(true),
       inside_begin_frame_deadline_interval_(false),
       needs_draw_(false),
       expecting_root_surface_damage_because_of_resize_(false),
       all_active_child_surfaces_ready_to_draw_(false),
       pending_swaps_(0),
       max_pending_swaps_(max_pending_swaps),
       observing_begin_frame_source_(false),
       root_surface_damaged_(false),
       expect_damage_from_root_surface_(false),
       weak_ptr_factory_(this) {
   begin_frame_deadline_closure_ = base::Bind(
       &DisplayScheduler::OnBeginFrameDeadline, weak_ptr_factory_.GetWeakPtr());
 
-  // TODO(tansell): Set this to something useful.
-  begin_frame_source_for_children_ = SyntheticBeginFrameSource::Create(
-      task_runner, BeginFrameArgs::DefaultInterval());
+  if (settings.disable_display_vsync) {

[enne (OOO), 2016/03/28 21:43:27]

I like the way this worked out, in terms of the DisplayScheduler making the
decision here about BeginFrameSource.

[sunnyps, 2016/03/28 23:09:48]

It feels like Display or BrowserCompositorOutputSurface should decide this. That
way we don't need an UpdateSchedulerBFS method or pass RendererSettings here.
But I'm OK with this approach too.

[enne (OOO), 2016/03/29 20:39:52]

I'll make Display do it, because Display already has the renderer settings.  I
don't know how this change will jive with a future world where DisplayScheduler
throttles slow renderers when vsync is disabled, but it shouldn't be hard to
solve that when we get there.

+    unthrottled_begin_frame_source_ =
+        BackToBackBeginFrameSource::Create(task_runner);
+    begin_frame_source_ = unthrottled_begin_frame_source_.get();
+  }
+
+  // TODO(enne): For now, this is always the same, so just set initially.
+  client_->UpdateSchedulerBeginFrameSource(begin_frame_source_);
 }
 
 DisplayScheduler::~DisplayScheduler() {
   if (observing_begin_frame_source_)
     begin_frame_source_->RemoveObserver(this);
 }
 
 // If we try to draw when the root surface resources are locked, the
 // draw will fail.
 void DisplayScheduler::SetRootSurfaceResourcesLocked(bool locked) {
@@ skipping 253 matching lines @@
 }
 
 void DisplayScheduler::DidSwapBuffersComplete() {
   pending_swaps_--;
   TRACE_EVENT_ASYNC_END1("cc", "DisplayScheduler:pending_swaps", this,
                          "pending_frames", pending_swaps_);
   ScheduleBeginFrameDeadline();
 }
 
 }  // namespace cc