Implement MD simple gesture nav

content/browser/web_contents/aura/gesture_nav_simple.h

 // Copyright 2014 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 CONTENT_BROWSER_WEB_CONTENTS_AURA_GESTURE_NAV_SIMPLE_H_
 #define CONTENT_BROWSER_WEB_CONTENTS_AURA_GESTURE_NAV_SIMPLE_H_
 
 #include <memory>
 
 #include "base/macros.h"
 #include "content/browser/renderer_host/overscroll_controller_delegate.h"
 
-namespace gfx {
-class Transform;
-}
-
-namespace ui {
-class Layer;
-}
-
 namespace content {
 
-class ArrowLayerDelegate;
 class WebContentsImpl;
 
 // A simple delegate for the overscroll controller that paints an arrow on top
 // of the web-contents as a hint for pending navigations from overscroll.
 class GestureNavSimple : public OverscrollControllerDelegate {
  public:
   explicit GestureNavSimple(WebContentsImpl* web_contents);
   ~GestureNavSimple() override;
 
  private:
-  void ApplyEffectsAndDestroy(const gfx::Transform& transform, float opacity);
+  class Affordance;
+
   void AbortGestureAnimation();
   void CompleteGestureAnimation();
-  bool ApplyEffectsForDelta(float delta_x);
 
   // OverscrollControllerDelegate:
   gfx::Rect GetVisibleBounds() const override;
-  // Returns true if the scroll update was consumed.
   bool OnOverscrollUpdate(float delta_x, float delta_y) override;
   void OnOverscrollComplete(OverscrollMode overscroll_mode) override;
   void OnOverscrollModeChange(OverscrollMode old_mode,
                               OverscrollMode new_mode) override;
 
   WebContentsImpl* web_contents_;
-  std::unique_ptr<ui::Layer> clip_layer_;
-  std::unique_ptr<ui::Layer> arrow_;
-  std::unique_ptr<ArrowLayerDelegate> arrow_delegate_;
+  std::unique_ptr<Affordance> affordance_;
   float completion_threshold_;
 
   DISALLOW_COPY_AND_ASSIGN(GestureNavSimple);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_WEB_CONTENTS_AURA_GESTURE_NAV_SIMPLE_H_