Revert of Remove indirection: setup scrollbar scroll layers in the scrollbar constructor

third_party/WebKit/Source/platform/testing/TestingPlatformSupport.cpp

 /*
  * Copyright (C) 2014 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 102 matching lines @@
 }
 
 std::unique_ptr<WebImageLayer> TestingCompositorSupport::createImageLayer() {
   return nullptr;
 }
 
 std::unique_ptr<WebScrollbarLayer>
 TestingCompositorSupport::createScrollbarLayer(
     std::unique_ptr<WebScrollbar>,
     WebScrollbarThemePainter,
-    std::unique_ptr<WebScrollbarThemeGeometry>,
-    WebLayer* scrollLayer) {
+    std::unique_ptr<WebScrollbarThemeGeometry>) {
   return nullptr;
 }
 
 std::unique_ptr<WebScrollbarLayer>
 TestingCompositorSupport::createOverlayScrollbarLayer(
     std::unique_ptr<WebScrollbar>,
     WebScrollbarThemePainter,
-    std::unique_ptr<WebScrollbarThemeGeometry>,
-    WebLayer* scrollLayer) {
+    std::unique_ptr<WebScrollbarThemeGeometry>) {
   return nullptr;
 }
 
 std::unique_ptr<WebScrollbarLayer>
 TestingCompositorSupport::createSolidColorScrollbarLayer(
     WebScrollbar::Orientation,
     int thumbThickness,
     int trackStart,
-    bool isLeftSideVerticalScrollbar,
-    WebLayer* scrollLayer) {
+    bool isLeftSideVerticalScrollbar) {
   return nullptr;
 }
 
 TestingPlatformSupport::TestingPlatformSupport()
     : TestingPlatformSupport(TestingPlatformSupport::Config()) {}
 
 TestingPlatformSupport::TestingPlatformSupport(const Config& config)
     : m_config(config),
       m_oldPlatform(Platform::current()),
       m_interfaceProvider(new TestingInterfaceProvider) {
@@ skipping 199 matching lines @@
   ThreadState::attachMainThread();
   ThreadState::current()->registerTraceDOMWrappers(nullptr, nullptr, nullptr,
                                                    nullptr);
   HTTPNames::init();
   FetchInitiatorTypeNames::init();
 }
 
 ScopedUnittestsEnvironmentSetup::~ScopedUnittestsEnvironmentSetup() {}
 
 }  // namespace blink