Implement top controls show/hide functionality for main thread scrolling

Source/web/PageWidgetDelegate.cpp

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 156 matching lines @@
     case WebInputEvent::GestureLongTap:
         return handler.handleGestureEvent(static_cast<const WebGestureEvent&>(event));
 
     case WebInputEvent::TouchStart:
     case WebInputEvent::TouchMove:
     case WebInputEvent::TouchEnd:
     case WebInputEvent::TouchCancel:
         if (!root || !root->view())
             return false;
         return handler.handleTouchEvent(*root, static_cast<const WebTouchEvent&>(event));
-
     case WebInputEvent::GesturePinchBegin:
     case WebInputEvent::GesturePinchEnd:
     case WebInputEvent::GesturePinchUpdate:
-        // FIXME: Once PlatformGestureEvent is updated to support pinch, this
-        // should call handleGestureEvent, just like it currently does for
-        // gesture scroll.
+        // Touchscreen pinch events are currently not handled in main thread. Once they are,
+        // these should be passed to |handleGestureEvent| similar to gesture scroll events.
         return false;
-
     default:
         return false;
     }
 }
 
 // ----------------------------------------------------------------
 // Default handlers for PageWidgetEventHandler
 
 void PageWidgetEventHandler::handleMouseMove(LocalFrame& mainFrame, const WebMouseEvent& event)
 {
@@ skipping 19 matching lines @@
 {
     return mainFrame.eventHandler().handleWheelEvent(PlatformWheelEventBuilder(mainFrame.view(), event));
 }
 
 bool PageWidgetEventHandler::handleTouchEvent(LocalFrame& mainFrame, const WebTouchEvent& event)
 {
     return mainFrame.eventHandler().handleTouchEvent(PlatformTouchEventBuilder(mainFrame.view(), event));
 }
 
 } // namespace blink