cc: Replace some instances of unordered_map with base::flat_map.

cc/surfaces/surface_aggregator.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_SURFACE_AGGREGATOR_H_
 #define CC_SURFACES_SURFACE_AGGREGATOR_H_
 
 #include <memory>
+#include <unordered_map>
 
 #include "base/containers/flat_map.h"
 #include "base/containers/flat_set.h"
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
 #include "cc/quads/draw_quad.h"
 #include "cc/quads/render_pass.h"
 #include "cc/resources/transferable_resource.h"
 #include "cc/surfaces/surface_id.h"
 #include "cc/surfaces/surfaces_export.h"
@@ skipping 187 matching lines @@
   SurfaceDrawQuadUmaStats uma_stats_;
 
   base::WeakPtrFactory<SurfaceAggregator> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(SurfaceAggregator);
 };
 
 }  // namespace cc
 
 #endif  // CC_SURFACES_SURFACE_AGGREGATOR_H_