Introduce bottom controls to CC and let it respond to scrolling

cc/trees/layer_tree.h

 // Copyright 2016 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_TREES_LAYER_TREE_H_
 #define CC_TREES_LAYER_TREE_H_
 
 #include <memory>
 
 #include <unordered_map>
@@ skipping 69 matching lines @@
     return inputs_.event_listener_properties[static_cast<size_t>(event_class)];
   }
 
   void SetViewportSize(const gfx::Size& device_viewport_size);
   gfx::Size device_viewport_size() const {
     return inputs_.device_viewport_size;
   }
 
   void SetTopControlsHeight(float height, bool shrink);
   void SetTopControlsShownRatio(float ratio);
+  void SetBottomControlsHeight(float height);
 
   void SetPageScaleFactorAndLimits(float page_scale_factor,
                                    float min_page_scale_factor,
                                    float max_page_scale_factor);
   float page_scale_factor() const { return inputs_.page_scale_factor; }
 
   void set_background_color(SkColor color) { inputs_.background_color = color; }
   SkColor background_color() const { return inputs_.background_color; }
 
   void set_has_transparent_background(bool transparent) {
@@ skipping 69 matching lines @@
 
     scoped_refptr<Layer> overscroll_elasticity_layer;
     scoped_refptr<Layer> page_scale_layer;
     scoped_refptr<Layer> inner_viewport_scroll_layer;
     scoped_refptr<Layer> outer_viewport_scroll_layer;
 
     float top_controls_height;
     float top_controls_shown_ratio;
     bool top_controls_shrink_blink_size;
 
+    float bottom_controls_height;
+
     float device_scale_factor;
     float painted_device_scale_factor;
     float page_scale_factor;
     float min_page_scale_factor;
     float max_page_scale_factor;
 
     SkColor background_color;
     bool has_transparent_background;
 
     LayerSelection selection;
@@ skipping 28 matching lines @@
 
   std::unique_ptr<AnimationHost> animation_host_;
   LayerTreeHost* layer_tree_host_;
 
   DISALLOW_COPY_AND_ASSIGN(LayerTree);
 };
 
 }  // namespace cc
 
 #endif  // CC_TREES_LAYER_TREE_H_