Controls offsets computed if either top or bottom are showing

cc/input/browser_controls_offset_manager.h

Index: cc/input/browser_controls_offset_manager.h
diff --git a/cc/input/browser_controls_offset_manager.h b/cc/input/browser_controls_offset_manager.h
index 401487c7aa2a2c37d65f980341bc2d95906fc090..aa35f52dbb87b9f1025a07d48362a847e90069db 100644
--- a/cc/input/browser_controls_offset_manager.h
+++ b/cc/input/browser_controls_offset_manager.h
@@ -95,8 +95,9 @@ class CC_EXPORT BrowserControlsOffsetManager
   // 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.