cc: Get rid of SurfaceDestroyed and use SurfaceDiscarded instead

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 <queue>
@@ skipping 100 matching lines @@
   surfaces_to_destroy_.erase(it);
   surface->set_destroyed(false);
   DCHECK_EQ(compositor_frame_sink_support.get(),
             surface->compositor_frame_sink_support().get());
   return surface;
 }
 
 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::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;
@@ skipping 426 matching lines @@
     std::vector<SurfaceId> children(iter->second.begin(), iter->second.end());
     std::sort(children.begin(), children.end());
 
     for (const SurfaceId& child_id : children)
       SurfaceReferencesToStringImpl(child_id, indent + "  ", str);
   }
 }
 #endif  // DCHECK_IS_ON()
 
 }  // namespace cc