Use nine-patch resource for drawing Aura overlay scrollbar thumb.

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("//cc/cc.gni")
 
 cc_component("cc") {
   sources = [
     "blimp/client_picture_cache.h",
@@ skipping 108 matching lines @@
     "layers/layer_position_constraint.cc",
     "layers/layer_position_constraint.h",
     "layers/layer_sticky_position_constraint.cc",
     "layers/layer_sticky_position_constraint.h",
     "layers/layer_utils.cc",
     "layers/layer_utils.h",
     "layers/nine_patch_layer.cc",
     "layers/nine_patch_layer.h",
     "layers/nine_patch_layer_impl.cc",
     "layers/nine_patch_layer_impl.h",
+    "layers/overlay_scrollbar_layer.cc",
+    "layers/overlay_scrollbar_layer.h",
+    "layers/overlay_scrollbar_layer_impl.cc",
+    "layers/overlay_scrollbar_layer_impl.h",
     "layers/paint_properties.h",
     "layers/painted_scrollbar_layer.cc",
     "layers/painted_scrollbar_layer.h",
     "layers/painted_scrollbar_layer_impl.cc",
     "layers/painted_scrollbar_layer_impl.h",
     "layers/picture_image_layer.cc",
     "layers/picture_image_layer.h",
     "layers/picture_layer.cc",
     "layers/picture_layer.h",
     "layers/picture_layer_impl.cc",
@@ skipping 168 matching lines @@
     "quads/content_draw_quad_base.cc",
     "quads/content_draw_quad_base.h",
     "quads/debug_border_draw_quad.cc",
     "quads/debug_border_draw_quad.h",
     "quads/draw_polygon.cc",
     "quads/draw_polygon.h",
     "quads/draw_quad.cc",
     "quads/draw_quad.h",
     "quads/largest_draw_quad.cc",
     "quads/largest_draw_quad.h",
+    "quads/nine_patch_generator.cc",
+    "quads/nine_patch_generator.h",
     "quads/picture_draw_quad.cc",
     "quads/picture_draw_quad.h",
     "quads/render_pass.cc",
     "quads/render_pass.h",
     "quads/render_pass_draw_quad.cc",
     "quads/render_pass_draw_quad.h",
     "quads/shared_quad_state.cc",
     "quads/shared_quad_state.h",
     "quads/solid_color_draw_quad.cc",
     "quads/solid_color_draw_quad.h",
@@ skipping 710 matching lines @@
   data = [
     "test/data/",
 
     # Needed for isolate script to execute.
     "//testing/scripts/common.py",
     "//testing/xvfb.py",
     "//testing/scripts/run_gtest_perf_test.py",
     "//tools/perf/generate_legacy_perf_dashboard_json.py",
   ]
 }