[cc] Plumb BeginFrameAcks through SurfaceManager to DisplayScheduler.

cc/surfaces/surface_observer.h

 // Copyright 2016 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_SURFACE_OBSERVER_H_
 #define CC_SURFACES_SURFACE_OBSERVER_H_
 
 namespace cc {
 
+struct BeginFrameAck;
+struct BeginFrameArgs;
+class SurfaceId;
 class SurfaceInfo;
 
 class SurfaceObserver {
  public:
-  // Runs when a CompositorFrame is received for the given SurfaceInfo for the
+  // Runs when a CompositorFrame is activated for the given SurfaceInfo for the
   // first time.
-  virtual void OnSurfaceCreated(const SurfaceInfo& surface_info) = 0;
+  virtual void OnSurfaceCreated(const SurfaceInfo& surface_info) {}

[sunnyps, 2017/05/22 06:46:38]

This should be a pure abstract class otherwise we might end up violating the
style guide (no multiple inheritance except interfaces) for subclasses.

[sunnyps, 2017/05/22 06:46:38]

Should we add the begin frame args and ack to SurfaceInfo to cover the begin
frame when the surface is created?

[Eric Seckler, 2017/05/22 15:32:15]

Done.

[Eric Seckler, 2017/05/22 15:32:15]

We could, but it's not really relevant in that situation, as SurfaceCreated is
only called when a CompositorFrame was submitted (and thus, a newly created
surface is always ready to draw). Let's add it later if we end up needing it?

 
-  // Runs when a Surface is damaged. *changed should be set to true if this
-  // causes a Display to be damaged.
-  virtual void OnSurfaceDamaged(const SurfaceId& surface_id, bool* changed) = 0;
+  // Runs when a Surface was marked to be destroyed.
+  virtual void OnSurfaceDestroyed(const SurfaceId& surface_id) {}
+
+  // Runs when a Surface is damaged (a new CompositorFrame is activated).
+  // *changed should be set to true if this causes a Display to be damaged.
+  virtual void OnSurfaceDamaged(const SurfaceId& surface_id, bool* changed) {}
+
+  // Runs when a Surface's CompositorFrame producer has received a BeginFrame.
+  virtual void OnSurfaceReceivedBeginFrame(const SurfaceId& surface_id,

[sunnyps, 2017/05/22 06:46:38]

bikeshed nit: OnSurfaceBeginFrame 

[Eric Seckler, 2017/05/22 15:32:15]

Done.

+                                           const BeginFrameArgs& args) {}
+
+  // Runs when a Surface's CompositorFrame producer has completed a BeginFrame
+  // either by submitting a CompositorFrame or confirming that it will not
+  // submit one.
+  virtual void OnSurfaceFinishedBeginFrame(const SurfaceId& surface_id,

[sunnyps, 2017/05/22 06:46:38]

bikeshed nit: OnSurfaceBeginFrameAck

[Eric Seckler, 2017/05/22 15:32:15]

Done.

+                                           const BeginFrameAck& ack) {}
 };
 
 }  // namespace cc
 
 #endif  // CC_SURFACES_SURFACE_OBSERVER_H_