cc: Use correct message loop proxy in BlockingTaskRunner

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 79 matching lines @@
       'resources/texture_uploader_unittest.cc',
       'resources/tile_manager_unittest.cc',
       'resources/tile_priority_unittest.cc',
       'resources/video_resource_updater_unittest.cc',
       'scheduler/delay_based_time_source_unittest.cc',
       'scheduler/scheduler_state_machine_unittest.cc',
       'scheduler/scheduler_unittest.cc',
       'test/layer_tree_json_parser_unittest.cc',
       'test/ordered_simple_task_runner_unittest.cc',
       'test/test_web_graphics_context_3d_unittest.cc',
+      'trees/blocking_task_runner_unittest.cc',
       'trees/damage_tracker_unittest.cc',
       'trees/layer_sorter_unittest.cc',
       'trees/layer_tree_host_common_unittest.cc',
       'trees/layer_tree_host_impl_unittest.cc',
       'trees/layer_tree_host_pixeltest_blending.cc',
       'trees/layer_tree_host_pixeltest_filters.cc',
       'trees/layer_tree_host_pixeltest_masks.cc',
       'trees/layer_tree_host_pixeltest_on_demand_raster.cc',
       'trees/layer_tree_host_pixeltest_readback.cc',
       'trees/layer_tree_host_unittest.cc',
@@ skipping 306 matching lines @@
             'variables': {
               'test_suite_name': 'cc_perftests',
             },
             'includes': [ '../build/apk_test.gypi' ],
           },
         ],
       }
     ]
   ],
 }