Controls offsets computed if either top or bottom are showing

cc/input/browser_controls_offset_manager.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_INPUT_BROWSER_CONTROLS_OFFSET_MANAGER_H_
 #define CC_INPUT_BROWSER_CONTROLS_OFFSET_MANAGER_H_
 
 #include <memory>
 
 #include "base/macros.h"
@@ skipping 77 matching lines @@
   float animation_start_value_;
   base::TimeTicks animation_stop_time_;
   float animation_stop_value_;
   AnimationDirection animation_direction_;
 
   BrowserControlsState permitted_state_;
 
   // Accumulated scroll delta since last baseline reset
   float accumulated_scroll_delta_;
 
-  // Content offset when last baseline reset occurred
-  float baseline_content_offset_;
+  // Content offset when last baseline reset occurred.
+  float baseline_top_content_offset_;
+  float baseline_bottom_content_offset_;
 
   // The percent height of the visible control such that it must be shown
   // when the user stops the scroll.
   float controls_show_threshold_;
 
   // The percent height of the visible control such that it must be hidden
   // when the user stops the scroll.
   float controls_hide_threshold_;
 
   bool pinch_gesture_active_;
 
   DISALLOW_COPY_AND_ASSIGN(BrowserControlsOffsetManager);
 };
 
 }  // namespace cc
 
 #endif  // CC_INPUT_BROWSER_CONTROLS_OFFSET_MANAGER_H_