Moves ownership of the cc::Display's BeginFrameSource out of Display.

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/auto_reset.h"
 #include "base/stl_util.h"
 #include "base/trace_event/trace_event.h"
 #include "cc/output/output_surface.h"
 
 namespace cc {
 
-DisplayScheduler::DisplayScheduler(BeginFrameSource* begin_frame_source,
-                                   base::SingleThreadTaskRunner* task_runner,
+DisplayScheduler::DisplayScheduler(base::SingleThreadTaskRunner* task_runner,
                                    int max_pending_swaps)
-    : begin_frame_source_(begin_frame_source),
+    : client_(nullptr),

[brianderson, 2016/12/09 19:01:57]

Thanks for fixing this!

+      begin_frame_source_(nullptr),
       task_runner_(task_runner),
       inside_surface_damaged_(false),
       visible_(false),
       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());
 }
 
 DisplayScheduler::~DisplayScheduler() {
   StopObservingBeginFrames();
 }
 
 void DisplayScheduler::SetClient(DisplaySchedulerClient* client) {
   client_ = client;
 }
 
+void DisplayScheduler::SetBeginFrameSource(

[brianderson, 2016/12/09 19:01:57]

For my understanding, was were the reasons to use SetBeginFrameSource rather
than passing it in to the constructor?

I see that it is:
Clearer from Display that its DisplayScheduler will have the same
BeginFrameSource.
Sets the DisplayScheduler's BeginFrameSource from fewer places.

Any others?

[Eric Seckler, 2016/12/12 09:27:18]

What you said :) Also, it's useful for later wrapping the Display's BFS  (with
something that can keep track of outstanding BeginFrames / observer responses,
see DisplayBeginFrameSource in https://codereview.chromium.org/2527283003/) and
providing the wrapped source to the scheduler.

+    BeginFrameSource* begin_frame_source) {
+  begin_frame_source_ = begin_frame_source;
+}
+
 void DisplayScheduler::SetVisible(bool visible) {
   if (visible_ == visible)
     return;
 
   visible_ = visible;
   // If going invisible, we'll stop observing begin frames once we try
   // to draw and fail.
   StartObservingBeginFrames();
   ScheduleBeginFrameDeadline();
 }
@@ skipping 304 matching lines @@
 }
 
 void DisplayScheduler::DidReceiveSwapBuffersAck() {
   pending_swaps_--;
   TRACE_EVENT_ASYNC_END1("cc", "DisplayScheduler:pending_swaps", this,
                          "pending_frames", pending_swaps_);
   ScheduleBeginFrameDeadline();
 }
 
 }  // namespace cc