Add SurfaceWillDraw notification

cc/surfaces/surface_manager.cc

 // 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.
 
 #include "cc/surfaces/surface_manager.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 109 matching lines @@
 
 void SurfaceManager::DestroySurface(std::unique_ptr<Surface> surface) {
   DCHECK(thread_checker_.CalledOnValidThread());
   surface->set_destroyed(true);
   for (auto& observer : observer_list_)
     observer.OnSurfaceDestroyed(surface->surface_id());
   surfaces_to_destroy_.push_back(std::move(surface));
   GarbageCollectSurfaces();
 }
 
+void SurfaceManager::SurfaceWillDraw(const SurfaceId& surface_id) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  for (auto& observer : observer_list_)
+    observer.OnSurfaceWillDraw(surface_id);
+}
+
 void SurfaceManager::RequireSequence(const SurfaceId& surface_id,
                                      const SurfaceSequence& sequence) {
   auto* surface = GetSurfaceForId(surface_id);
   if (!surface) {
     DLOG(ERROR) << "Attempting to require callback on nonexistent surface";
     return;
   }
   surface->AddDestructionDependency(sequence);
 }
 
@@ skipping 419 matching lines @@
   *str << "\n";
 
   // If the current surface has references to children, sort children and print
   // references for each child.
   for (const SurfaceId& child_id : GetSurfacesReferencedByParent(surface_id))
     SurfaceReferencesToStringImpl(child_id, indent + "  ", str);
 }
 #endif  // DCHECK_IS_ON()
 
 }  // namespace cc