Deleted ScrollbarLayerImplBase arg from ScrollbarController methods.

This CL gets rid of the several ScrollbarLayerImplBase references in
the private methods of ScrollbarController. They need not be passed
around because the ScrollbarLayerImplBase can easily be looked up by
calling ScrollbarController::ScrollbarLayer (which retrieves the needed
scrollber layer by using CapturedScrollbarMetadata::scroll_element_id).

Bug: 1077093
Change-Id: I2bb48b4fe61227e6e89c4dff8cef4064a20e3965
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2174809
Commit-Queue: Rahul Arakeri <arakeri@microsoft.com>
Reviewed-by: David Bokan <bokan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#765347}

cc/input/scrollbar_controller.h

@@ -127,16 +127,9 @@ class CC_EXPORT ScrollbarController {
   InputHandlerPointerResult HandlePointerUp(
       const gfx::PointF position_in_widget);
 
-  // "velocity" here is calculated based on the initial scroll delta (See
-  // InitialDeltaToAutoscrollVelocity). This value carries a "sign" which is
-  // needed to determine whether we should set up the autoscrolling in the
-  // forwards or the backwards direction.
-  void StartAutoScrollAnimation(float velocity,
-                                const ScrollbarLayerImplBase* scrollbar,
-                                ScrollbarPart pressed_scrollbar_part);
-  bool ScrollbarScrollIsActive() { return scrollbar_scroll_is_active_; }
+  bool ScrollbarScrollIsActive() const { return scrollbar_scroll_is_active_; }
   void DidUnregisterScrollbar(ElementId element_id);
-  ScrollbarLayerImplBase* ScrollbarLayer();
+  ScrollbarLayerImplBase* ScrollbarLayer() const;
   void WillBeginImplFrame();
   void ResetState();
 
@@ -187,44 +180,42 @@ class CC_EXPORT ScrollbarController {
     ScrollbarOrientation orientation;
   };
 
+  // "velocity" here is calculated based on the initial scroll delta (See
+  // InitialDeltaToAutoscrollVelocity). This value carries a "sign" which is
+  // needed to determine whether we should set up the autoscrolling in the
+  // forwards or the backwards direction.
+  void StartAutoScrollAnimation(float velocity,
+                                ScrollbarPart pressed_scrollbar_part);
+
   // Returns the DSF based on whether use-zoom-for-dsf is enabled.
   float ScreenSpaceScaleFactor() const;
 
   // Helper to convert scroll offset to autoscroll velocity.
-  float InitialDeltaToAutoscrollVelocity(
-      const ScrollbarLayerImplBase* scrollbar,
-      gfx::ScrollOffset scroll_offset) const;
+  float InitialDeltaToAutoscrollVelocity(gfx::ScrollOffset scroll_offset) const;
 
   // Returns the hit tested ScrollbarPart based on the position_in_widget.
   ScrollbarPart GetScrollbarPartFromPointerDown(
-      const ScrollbarLayerImplBase* scrollbar,
-      const gfx::PointF position_in_widget);
+      const gfx::PointF position_in_widget) const;
 
   // Returns scroll offsets based on which ScrollbarPart was hit tested.
   gfx::ScrollOffset GetScrollOffsetForScrollbarPart(
-      const ScrollbarLayerImplBase* scrollbar,
       const ScrollbarPart scrollbar_part,
-      const bool shift_modifier);
+      const bool shift_modifier) const;
 
   // Returns the rect for the ScrollbarPart.
-  gfx::Rect GetRectForScrollbarPart(const ScrollbarLayerImplBase* scrollbar,
-                                    const ScrollbarPart scrollbar_part);
+  gfx::Rect GetRectForScrollbarPart(const ScrollbarPart scrollbar_part) const;
 
-  LayerImpl* GetLayerHitByPoint(const gfx::PointF position_in_widget);
-  int GetScrollDeltaForScrollbarPart(const ScrollbarLayerImplBase* scrollbar,
-                                     const ScrollbarPart scrollbar_part,
-                                     const bool shift_modifier);
+  LayerImpl* GetLayerHitByPoint(const gfx::PointF position_in_widget) const;
+  int GetScrollDeltaForScrollbarPart(const ScrollbarPart scrollbar_part,
+                                     const bool shift_modifier) const;
 
   // Makes position_in_widget relative to the scrollbar.
-  gfx::PointF GetScrollbarRelativePosition(
-      const ScrollbarLayerImplBase* scrollbar,
-      const gfx::PointF position_in_widget,
-      bool* clipped);
+  gfx::PointF GetScrollbarRelativePosition(const gfx::PointF position_in_widget,
+                                           bool* clipped) const;
 
   // Decides if the scroller should snap to the offset that it was originally at
   // (i.e the offset before the thumb drag).
-  bool SnapToDragOrigin(const ScrollbarLayerImplBase* scrollbar,
-                        const gfx::PointF pointer_position_in_widget);
+  bool SnapToDragOrigin(const gfx::PointF pointer_position_in_widget) const;
 
   // Decides whether a track autoscroll should be aborted (or restarted) due to
   // the thumb reaching the pointer or the pointer leaving (or re-entering) the
@@ -233,22 +224,21 @@ class CC_EXPORT ScrollbarController {
 
   // Shift (or "Option" in case of Mac) + click is expected to do a non-animated
   // jump to a certain offset.
-  float GetScrollDeltaForAbsoluteJump(const ScrollbarLayerImplBase* scrollbar);
+  float GetScrollDeltaForAbsoluteJump() const;
 
   // Determines if the delta needs to be animated.
   ui::ScrollGranularity Granularity(const ScrollbarPart scrollbar_part,
-                                    bool shift_modifier);
+                                    bool shift_modifier) const;
 
   // Calculates the delta based on position_in_widget and drag_origin.
   int GetScrollDeltaForDragPosition(
-      const ScrollbarLayerImplBase* scrollbar,
-      const gfx::PointF pointer_position_in_widget);
+      const gfx::PointF pointer_position_in_widget) const;
 
   // Returns the ratio of the scroller length to the scrollbar length. This is
   // needed to scale the scroll delta for thumb drag.
-  float GetScrollerToScrollbarRatio(const ScrollbarLayerImplBase* scrollbar);
+  float GetScrollerToScrollbarRatio() const;
 
-  int GetViewportLength(const ScrollbarLayerImplBase* scrollbar) const;
+  int GetViewportLength() const;
 
   LayerTreeHostImpl* layer_tree_host_impl_;