Move PixelRefMap and its Iterator out from Picture class

cc/cc.gyp

 # Copyright (c) 2012 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.
 
 {
   'variables': {
     'chromium_code': 1,
   },
   'targets': [
     {
@@ skipping 399 matching lines @@
         'resources/picture_layer_tiling.cc',
         'resources/picture_layer_tiling.h',
         'resources/picture_layer_tiling_set.cc',
         'resources/picture_layer_tiling_set.h',
         'resources/picture_pile.cc',
         'resources/picture_pile.h',
         'resources/picture_pile_impl.cc',
         'resources/picture_pile_impl.h',
         'resources/pixel_buffer_tile_task_worker_pool.cc',
         'resources/pixel_buffer_tile_task_worker_pool.h',
+        'resources/pixel_ref_map.cc',
+        'resources/pixel_ref_map.h',
         'resources/platform_color.h',
         'resources/prioritized_resource.cc',
         'resources/prioritized_resource.h',
         'resources/prioritized_resource_manager.cc',
         'resources/prioritized_resource_manager.h',
         'resources/priority_calculator.cc',
         'resources/priority_calculator.h',
         'resources/raster_buffer.cc',
         'resources/raster_buffer.h',
         'resources/raster_source.h',
@@ skipping 178 matching lines @@
         'surfaces/surface_resource_holder.cc',
         'surfaces/surface_resource_holder.h',
         'surfaces/surfaces_export.h',
       ],
       'includes': [
         '../build/android/increase_size_for_speed.gypi',
       ],
     },
   ],
 }