Add pixel tests for rastering painted scrollbars at different scales.

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.
 
 import("//build/config/ui.gni")
 import("//testing/test.gni")
 
 component("cc") {
   sources = [
     "animation/animation.cc",
@@ skipping 900 matching lines @@
     "tiles/tile_manager_unittest.cc",
     "tiles/tile_priority_unittest.cc",
     "trees/blocking_task_runner_unittest.cc",
     "trees/damage_tracker_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_readback.cc",
+    "trees/layer_tree_host_pixeltest_scrollbars.cc",
     "trees/layer_tree_host_pixeltest_synchronous.cc",
     "trees/layer_tree_host_pixeltest_tiles.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_occlusion.cc",
     "trees/layer_tree_host_unittest_picture.cc",
     "trees/layer_tree_host_unittest_proxy.cc",
@@ skipping 105 matching lines @@
     "//ui/gfx/geometry",
     "//ui/gl",
     "//ui/gl:test_support",
   ]
 
   # This target should not require the Chrome executable to run.
   assert_no_deps = [ "//chrome" ]
 }
 # When adding support for isolates, please have a look at run-time dependencies
 # in the cc_unittests_run target in cc_tests.gyp.