Ensure Surface size always matches window size on swap

cc/surfaces/surface_aggregator.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_aggregator.h"
 
 #include <map>
 
 #include "base/bind.h"
 #include "base/containers/hash_tables.h"
@@ skipping 398 matching lines @@
   SurfaceSet::iterator it = referenced_surfaces_.insert(surface_id).first;
 
   dest_resource_list_ = &frame->delegated_frame_data->resource_list;
   dest_pass_list_ = &frame->delegated_frame_data->render_pass_list;
 
   CopyPasses(root_surface_frame->delegated_frame_data.get(), surface);
 
   referenced_surfaces_.erase(it);
   DCHECK(referenced_surfaces_.empty());
 
+  if (dest_pass_list_->empty())
+    return nullptr;
+
   dest_pass_list_ = NULL;
   RemoveUnreferencedChildren();
   contained_surfaces_.swap(previous_contained_surfaces_);
   contained_surfaces_.clear();
 
   for (SurfaceIndexMap::iterator it = previous_contained_surfaces_.begin();
        it != previous_contained_surfaces_.end();
        ++it) {
     Surface* surface = manager_->GetSurfaceForId(it->first);
     if (surface)
       surface->TakeLatencyInfo(&frame->metadata.latency_info);
   }
 
   // TODO(jamesr): Aggregate all resource references into the returned frame's
   // resource list.
 
   return frame.Pass();
 }
 
 }  // namespace cc