cc: Plumbing for BeginFrameSource based on Surfaces

cc/surfaces/onscreen_display_client.h

 // Copyright 2014 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.
 
 #ifndef CC_SURFACES_ONSCREEN_DISPLAY_CLIENT_H_
 #define CC_SURFACES_ONSCREEN_DISPLAY_CLIENT_H_
 
 #include "cc/surfaces/display_client.h"
 
 #include "base/compiler_specific.h"
@@ skipping 35 matching lines @@
   // DisplayClient implementation.
   void CommitVSyncParameters(base::TimeTicks timebase,
                              base::TimeDelta interval) override;
   void OutputSurfaceLost() override;
   void SetMemoryPolicy(const ManagedMemoryPolicy& policy) override;
 
   bool output_surface_lost() { return output_surface_lost_; }
 
  protected:
   scoped_ptr<OutputSurface> output_surface_;
-  scoped_ptr<Display> display_;
+  // Be careful of destruction order:
+  // Display depends on DisplayScheduler depends on *BeginFrameSource
+  // depends on TaskRunner.

[mithro-old, 2015/10/01 03:00:23]

Can we use asserts/dchecks to make sure the destruction happens in the right
order?

[brianderson, 2015/10/07 20:54:48]

Trying to think of how to do that, but it's difficult since the classes here are
given non-owning pointers and are not notified that something they depend on is
going to be destroyed.
 
The trybots caught it, so I'm not too worried about this regressing.

+  scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
   scoped_ptr<SyntheticBeginFrameSource> synthetic_frame_source_;
   scoped_ptr<BackToBackBeginFrameSource> unthrottled_frame_source_;
   scoped_ptr<DisplayScheduler> scheduler_;
-  scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
+  scoped_ptr<Display> display_;
   SurfaceDisplayOutputSurface* surface_display_output_surface_;
   bool output_surface_lost_;
   bool disable_display_vsync_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(OnscreenDisplayClient);
 };
 
 }  // namespace cc
 
 #endif  // CC_SURFACES_ONSCREEN_DISPLAY_CLIENT_H_