Add preventPropagation bit to GestureScrollUpdate event

Source/core/page/EventHandler.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2012 Digia Plc. and/or its subsidiary(-ies)
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
@@ skipping 2447 matching lines @@
         return sendScrollEventToView(gestureEvent, delta);
 
     // Ignore this event if the targeted node does not have a valid renderer.
     RenderObject* renderer = node->renderer();
     if (!renderer)
         return false;
 
     RefPtrWillBeRawPtr<FrameView> protector(m_frame->view());
 
     Node* stopNode = nullptr;
-    bool scrollShouldNotPropagate = gestureEvent.type() == PlatformEvent::GestureScrollUpdateWithoutPropagation;
+    bool scrollShouldNotPropagate = gestureEvent.type() == PlatformEvent::GestureScrollUpdateWithoutPropagation
+        || (gestureEvent.type() == PlatformEvent::GestureScrollUpdate && gestureEvent.preventPropagation());
 
     // Try to send the event to the correct view.
     if (passScrollGestureEventToWidget(gestureEvent, renderer)) {
         if(scrollShouldNotPropagate)
               m_previousGestureScrolledNode = m_scrollGestureHandlingNode;
 
         return true;
     }
 
     if (scrollShouldNotPropagate)
@@ skipping 1388 matching lines @@
 unsigned EventHandler::accessKeyModifiers()
 {
 #if OS(MACOSX)
     return PlatformEvent::CtrlKey | PlatformEvent::AltKey;
 #else
     return PlatformEvent::AltKey;
 #endif
 }
 
 } // namespace blink