Move PixelRefMap and its Iterator out from Picture class

cc/cc_tests.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,
     'cc_unit_tests_source_files': [
       'animation/animation_unittest.cc',
       'animation/keyframed_animation_curve_unittest.cc',
@@ skipping 65 matching lines @@
       'quads/draw_quad_unittest.cc',
       'quads/list_container_unittest.cc',
       'quads/render_pass_unittest.cc',
       'resources/display_item_list_unittest.cc',
       'resources/layer_quad_unittest.cc',
       'resources/picture_layer_tiling_set_unittest.cc',
       'resources/picture_layer_tiling_unittest.cc',
       'resources/picture_pile_impl_unittest.cc',
       'resources/picture_pile_unittest.cc',
       'resources/picture_unittest.cc',
+      'resources/pixel_ref_map_unittest.cc',
       'resources/prioritized_resource_unittest.cc',
       'resources/tile_task_worker_pool_unittest.cc',
       'resources/resource_provider_unittest.cc',
       'resources/resource_update_controller_unittest.cc',
       'resources/scoped_gpu_raster_unittest.cc',
       'resources/scoped_resource_unittest.cc',
       'resources/task_graph_runner_unittest.cc',
       'resources/texture_mailbox_deleter_unittest.cc',
       'resources/texture_uploader_unittest.cc',
       'resources/tile_manager_unittest.cc',
@@ skipping 361 matching lines @@
             '../build/isolate.gypi',
           ],
           'sources': [
             'cc_unittests.isolate',
           ],
         },
       ],
     }],
   ],
 }