Adjust maximum scroll bounds on FrameView to account for top controls. (Blink-side)

public/web/WebWidget.h

Index: public/web/WebWidget.h
diff --git a/public/web/WebWidget.h b/public/web/WebWidget.h
index 5a7a80234b8aa97843930d54bc3711b4ab65a968..92178a9c3ac098fd136e999ede7b5c4be213a8e2 100644
--- a/public/web/WebWidget.h
+++ b/public/web/WebWidget.h
@@ -262,6 +262,9 @@ public:
     // but not the select popup.
     virtual WebPagePopup* pagePopup() const { return 0; }
 
+    // Sets the height subtracted from the Widget to accomodate the top controls.
+    virtual void setTopControlsLayoutHeight(float) { }
+
 protected:
     ~WebWidget() { }
 };