Support single-threaded impl-side painting

cc/BUILD.gn

 # 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.
 
 component("cc") {
   sources = [
     "animation/animation.cc",
     "animation/animation.h",
     "animation/animation_curve.cc",
     "animation/animation_curve.h",
@@ skipping 734 matching lines @@
     "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_pixeltest_synchronous.cc",
     "trees/layer_tree_host_unittest.cc",
     "trees/layer_tree_host_unittest_animation.cc",
     "trees/layer_tree_host_unittest_context.cc",
     "trees/layer_tree_host_unittest_copyrequest.cc",
     "trees/layer_tree_host_unittest_damage.cc",
     "trees/layer_tree_host_unittest_delegated.cc",
     "trees/layer_tree_host_unittest_occlusion.cc",
     "trees/layer_tree_host_unittest_no_message_loop.cc",
     "trees/layer_tree_host_unittest_picture.cc",
     "trees/layer_tree_host_unittest_proxy.cc",
@@ skipping 59 matching lines @@
     "//gpu/command_buffer/common:gles2_utils",
     "//media",
     "//skia",
     "//testing/gmock",
     "//testing/gtest",
     "//testing/perf",
     "//ui/gfx",
     "//ui/gfx/geometry",
   ]
 }