Revert of Cleanup viewport scrolling for future scroll customization work.

cc/layers/viewport.h

 // Copyright 2015 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_LAYERS_VIEWPORT_H_
 #define CC_LAYERS_VIEWPORT_H_
 
 #include "base/memory/scoped_ptr.h"
 #include "cc/layers/layer_impl.h"
 #include "ui/gfx/geometry/vector2d_f.h"
 
 namespace cc {
 
 class LayerTreeHostImpl;
 
 // Encapsulates gesture handling logic on the viewport layers. The "viewport"
 // is made up of two scrolling layers, the inner viewport (visual) and the
 // outer viewport (layout) scroll layers. These layers have different scroll
 // bubbling behavior from the rest of the layer tree which is encoded in this
 // class.
 class CC_EXPORT Viewport {
  public:
   // If the pinch zoom anchor on the first PinchUpdate is within this length
   // of the screen edge, "snap" the zoom to that edge. Experimentally
   // determined.
   static const int kPinchZoomSnapMarginDips = 100;
 
+  struct ScrollResult {
+    gfx::Vector2dF applied_delta;
+    gfx::Vector2dF unused_scroll_delta;
+    gfx::Vector2dF top_controls_applied_delta;
+  };
+
   static scoped_ptr<Viewport> Create(LayerTreeHostImpl* host_impl);
 
   // Differs from scrolling in that only the visual viewport is moved, without
   // affecting the top controls or outer viewport.
   void Pan(const gfx::Vector2dF& delta);
 
   // Scrolls the viewport, applying the unique bubbling between the inner and
   // outer viewport. Scrolls can be consumed by top controls.
-  gfx::Vector2dF ScrollBy(const gfx::Vector2dF& delta,
-                          const gfx::Point& viewport_point,
-                          bool is_direct_manipulation,
-                          bool affect_top_controls);
+  ScrollResult ScrollBy(const gfx::Vector2dF& delta,
+                        const gfx::Point& viewport_point,
+                        bool is_wheel_scroll,
+                        bool affect_top_controls);
 
   void PinchUpdate(float magnify_delta, const gfx::Point& anchor);
   void PinchEnd();
 
  private:
   explicit Viewport(LayerTreeHostImpl* host_impl);
 
   bool ShouldTopControlsConsumeScroll(const gfx::Vector2dF& scroll_delta) const;
   gfx::Vector2dF AdjustOverscroll(const gfx::Vector2dF& delta) const;
 
@@ skipping 15 matching lines @@
   // The pinch zoom anchor point is adjusted by this amount during a pinch. This
   // is used to "snap" a pinch-zoom to the edge of the screen.
   gfx::Vector2d pinch_anchor_adjustment_;
 
   DISALLOW_COPY_AND_ASSIGN(Viewport);
 };
 
 }  // namespace cc
 
 #endif  // CC_LAYERS_VIEWPORT_H_