Refactor LayerTreeImpl's scrollbar map to be keyed on element ids

cc/input/scrollbar_animation_controller.h

 // Copyright 2012 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.
 
 #ifndef CC_INPUT_SCROLLBAR_ANIMATION_CONTROLLER_H_
 #define CC_INPUT_SCROLLBAR_ANIMATION_CONTROLLER_H_
 
 #include "base/cancelable_callback.h"
 #include "base/memory/weak_ptr.h"
 #include "base/time/time.h"
 #include "cc/cc_export.h"
 #include "cc/input/single_scrollbar_animation_controller_thinning.h"
 #include "cc/layers/layer_impl.h"
 #include "cc/layers/scrollbar_layer_impl_base.h"
 #include "ui/gfx/geometry/vector2d_f.h"
 
 namespace cc {
 
 class CC_EXPORT ScrollbarAnimationControllerClient {
  public:
   virtual void PostDelayedScrollbarAnimationTask(const base::Closure& task,
                                                  base::TimeDelta delay) = 0;
   virtual void SetNeedsRedrawForScrollbarAnimation() = 0;
   virtual void SetNeedsAnimateForScrollbarAnimation() = 0;
   virtual void DidChangeScrollbarVisibility() = 0;
-  virtual ScrollbarSet ScrollbarsFor(int scroll_layer_id) const = 0;
+  virtual ScrollbarSet ScrollbarsFor(ElementId scroll_element_id) const = 0;
 
  protected:
   virtual ~ScrollbarAnimationControllerClient() {}
 };
 
 // This class show scrollbars when scroll and fade out after an idle delay.
 // The fade animations works on both scrollbars and is controlled in this class
 // This class also passes the mouse state to each
 // SingleScrollbarAnimationControllerThinning. The thinning animations are
 // independent between vertical/horizontal and are managed by the
 // SingleScrollbarAnimationControllerThinnings.
 class CC_EXPORT ScrollbarAnimationController {
  public:
   // ScrollbarAnimationController for Android. It only has show & fade out
   // animation.
   static std::unique_ptr<ScrollbarAnimationController>
   CreateScrollbarAnimationControllerAndroid(
-      int scroll_layer_id,
+      ElementId scroll_element_id,
       ScrollbarAnimationControllerClient* client,
       base::TimeDelta fade_out_delay,
       base::TimeDelta fade_out_resize_delay,
       base::TimeDelta fade_out_duration);
 
   // ScrollbarAnimationController for Desktop Overlay Scrollbar. It has show &
   // fade out animation and thinning animation.
   static std::unique_ptr<ScrollbarAnimationController>
   CreateScrollbarAnimationControllerAuraOverlay(
-      int scroll_layer_id,
+      ElementId scroll_element_id,
       ScrollbarAnimationControllerClient* client,
       base::TimeDelta show_delay,
       base::TimeDelta fade_out_delay,
       base::TimeDelta fade_out_resize_delay,
       base::TimeDelta fade_out_duration,
       base::TimeDelta thinning_duration);
 
   ~ScrollbarAnimationController();
 
   bool ScrollbarsHidden() const;
@@ skipping 24 matching lines @@
   // ScrollableArea::showOverlayScrollbars).
   void DidRequestShowFromMainThread();
 
   bool MouseIsOverScrollbar(ScrollbarOrientation orientation) const;
   bool MouseIsNearScrollbar(ScrollbarOrientation orientation) const;
   bool MouseIsNearAnyScrollbar() const;
 
   static constexpr float kMouseMoveDistanceToTriggerShow = 30.0f;
 
  private:
-  ScrollbarAnimationController(int scroll_layer_id,
+  ScrollbarAnimationController(ElementId scroll_element_id,
                                ScrollbarAnimationControllerClient* client,
                                base::TimeDelta fade_out_delay,
                                base::TimeDelta fade_out_resize_delay,
                                base::TimeDelta fade_out_duration);
 
-  ScrollbarAnimationController(int scroll_layer_id,
+  ScrollbarAnimationController(ElementId scroll_element_id,
                                ScrollbarAnimationControllerClient* client,
                                base::TimeDelta show_delay,
                                base::TimeDelta fade_out_delay,
                                base::TimeDelta fade_out_resize_delay,
                                base::TimeDelta fade_out_duration,
                                base::TimeDelta thinning_duration);
 
   ScrollbarSet Scrollbars() const;
   SingleScrollbarAnimationControllerThinning& GetScrollbarAnimationController(
       ScrollbarOrientation) const;
@@ skipping 25 matching lines @@
   // show_delay_ is only for the case where the mouse hovers near the screen
   // edge.
   base::TimeDelta show_delay_;
   base::TimeDelta fade_out_delay_;
   base::TimeDelta fade_out_resize_delay_;
 
   bool need_trigger_scrollbar_show_;
 
   bool is_animating_;
 
-  const int scroll_layer_id_;
+  const ElementId scroll_element_id_;
   bool currently_scrolling_;
   bool show_in_fast_scroll_;
 
   base::CancelableClosure delayed_scrollbar_show_;
   base::CancelableClosure delayed_scrollbar_fade_out_;
 
   float opacity_;
   base::TimeDelta fade_out_duration_;
 
   const bool show_scrollbars_on_scroll_gesture_;
   const bool need_thinning_animation_;
   std::unique_ptr<SingleScrollbarAnimationControllerThinning>
       vertical_controller_;
   std::unique_ptr<SingleScrollbarAnimationControllerThinning>
       horizontal_controller_;
 
   base::WeakPtrFactory<ScrollbarAnimationController> weak_factory_;
 };
 
 }  // namespace cc
 
 #endif  // CC_INPUT_SCROLLBAR_ANIMATION_CONTROLLER_H_