Prevent overlay scrollbars expand or hover together

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")
 import("//testing/test.gni")
 
 cc_component("cc") {
   sources = [
@@ skipping 77 matching lines @@
     "input/scroll_state.h",
     "input/scroll_state_data.cc",
     "input/scroll_state_data.h",
     "input/scrollbar_animation_controller.cc",
     "input/scrollbar_animation_controller.h",
     "input/scrollbar_animation_controller_linear_fade.cc",
     "input/scrollbar_animation_controller_linear_fade.h",
     "input/scrollbar_animation_controller_thinning.cc",
     "input/scrollbar_animation_controller_thinning.h",
     "input/selection.h",
+    "input/single_scrollbar_animation_controller_thinning.cc",
+    "input/single_scrollbar_animation_controller_thinning.h",
     "layers/append_quads_data.h",
     "layers/content_layer_client.h",
     "layers/draw_properties.cc",
     "layers/draw_properties.h",
     "layers/empty_content_layer_client.cc",
     "layers/empty_content_layer_client.h",
     "layers/heads_up_display_layer.cc",
     "layers/heads_up_display_layer.h",
     "layers/heads_up_display_layer_impl.cc",
     "layers/heads_up_display_layer_impl.h",
@@ skipping 933 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",
   ]
 }