Fix cc scrollbar layer issues with initialization, and use element ids throughout.

cc/layers/solid_color_scrollbar_layer.cc

 // Copyright 2013 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.
 
 #include "cc/layers/solid_color_scrollbar_layer.h"
 
 #include <memory>
 
 #include "cc/layers/layer_impl.h"
 #include "cc/layers/solid_color_scrollbar_layer_impl.h"
@@ skipping 73 matching lines @@
 }
 
 void SolidColorScrollbarLayer::SetNeedsDisplayRect(const gfx::Rect& rect) {
   // Never needs repaint.
 }
 
 bool SolidColorScrollbarLayer::OpacityCanAnimateOnImplThread() const {
   return true;
 }
 
-bool SolidColorScrollbarLayer::AlwaysUseActiveTreeOpacity() const {
-  return true;
-}
-
 ElementId SolidColorScrollbarLayer::scroll_element_id() const {
   return solid_color_scrollbar_layer_inputs_.scroll_element_id;
 }
 
 void SolidColorScrollbarLayer::SetScrollElementId(ElementId element_id) {
   if (element_id == solid_color_scrollbar_layer_inputs_.scroll_element_id)
     return;
 
   solid_color_scrollbar_layer_inputs_.scroll_element_id = element_id;
   SetNeedsFullTreeSync();
 }
 
 ScrollbarOrientation SolidColorScrollbarLayer::orientation() const {
   return solid_color_scrollbar_layer_inputs_.orientation;
 }
 
 }  // namespace cc