Introduce bottom controls to CC and let it respond to scrolling

cc/input/top_controls_manager.h

 // 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.
 
 #ifndef CC_INPUT_TOP_CONTROLS_MANAGER_H_
 #define CC_INPUT_TOP_CONTROLS_MANAGER_H_
 
 #include <memory>
 
 #include "base/macros.h"
@@ skipping 18 matching lines @@
     SHOWING_CONTROLS,
     HIDING_CONTROLS
   };
 
   static std::unique_ptr<TopControlsManager> Create(
       TopControlsManagerClient* client,
       float top_controls_show_threshold,
       float top_controls_hide_threshold);
   virtual ~TopControlsManager();
 
+  // The offset from the window top to the top edge of the controls. Runs from 0
+  // (controls fully shown) to negative values (down is positive).
   float ControlsTopOffset() const;
+  // The amount of offset of the web content area. Same as the current shown
+  // height of the top controls.
   float ContentTopOffset() const;
   float TopControlsShownRatio() const;
   float TopControlsHeight() const;
 
+  // The amount of offset to translate the bottom controls. 0 or positive value.
+  float ControlsBottomOffset() const;
+  // The amount of offset of the web content area, calculating from the bottom.
+  // Same as the current shown height of the bottom controls.
+  float ContentBottomOffset() const;
+  // Similar to TopControlsHeight(), this method should return a static value.
+  // The current animated height can be got from ContentBottomOffset().
+  float BottomControlsHeight() const;
+
   bool has_animation() const { return animation_direction_ != NO_ANIMATION; }
   AnimationDirection animation_direction() { return animation_direction_; }
 
   void UpdateTopControlsState(TopControlsState constraints,
                               TopControlsState current,
                               bool animate);
 
   void ScrollBegin();
   gfx::Vector2dF ScrollBy(const gfx::Vector2dF& pending_delta);
   void ScrollEnd();
@@ skipping 45 matching lines @@
   float top_controls_hide_threshold_;
 
   bool pinch_gesture_active_;
 
   DISALLOW_COPY_AND_ASSIGN(TopControlsManager);
 };
 
 }  // namespace cc
 
 #endif  // CC_INPUT_TOP_CONTROLS_MANAGER_H_