compositor worker: Use a WebThread for the compositor thread.

components/scheduler/scheduler.gypi

 # Copyright 2015 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': {
     'scheduler_common_sources': [
       'common/scheduler_switches.cc',
       'common/scheduler_switches.h',
     ],
@@ skipping 19 matching lines @@
       'base/work_queue.h',
       'base/work_queue_sets.cc',
       'base/work_queue_sets.h',
       'base/pollable_thread_safe_flag.cc',
       'base/pollable_thread_safe_flag.h',
       'base/virtual_time_domain.cc',
       'base/virtual_time_domain.h',
       'base/enqueue_order.h',
       'base/enqueue_order.cc',
       'child/child_scheduler.h',
+      'child/compositor_worker_scheduler.cc',
+      'child/compositor_worker_scheduler.h',
       'child/idle_helper.cc',
       'child/idle_helper.h',
       'child/scheduler_helper.cc',
       'child/scheduler_helper.h',
       'child/scheduler_tqm_delegate.h',
       'child/scheduler_tqm_delegate_impl.cc',
       'child/scheduler_tqm_delegate_impl.h',
       'child/single_thread_idle_task_runner.cc',
       'child/single_thread_idle_task_runner.h',
       'child/virtual_time_tqm_delegate.cc',
@@ skipping 37 matching lines @@
       'renderer/webthread_impl_for_renderer_scheduler.cc',
       'renderer/webthread_impl_for_renderer_scheduler.h',
       'scheduler_export.h',
     ],
     'scheduler_test_support_sources': [
       'test/lazy_scheduler_message_loop_delegate_for_tests.cc',
       'test/lazy_scheduler_message_loop_delegate_for_tests.h',
     ],
   },
 }