Merge 106476 - Source/WebCore: preventDefault() in a mousedown in a subframe should not

Source/WebCore/page/EventHandler.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  *
  * 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.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 1443 matching lines @@
             m_resizeLayer = layer;
             m_offsetFromResizeCorner = layer->offsetFromResizeCorner(p);
             invalidateClick();
             return true;
         }
     }
 
     m_frame->selection()->setCaretBlinkingSuspended(true);
 
     bool swallowEvent = dispatchMouseEvent(eventNames().mousedownEvent, targetNode(mev), true, m_clickCount, mouseEvent, true);
-    m_capturesDragging = !swallowEvent;
+    m_capturesDragging = !swallowEvent || mev.scrollbar();
 
     // If the hit testing originally determined the event was in a scrollbar, refetch the MouseEventWithHitTestResults
     // in case the scrollbar widget was destroyed when the mouse event was handled.
     if (mev.scrollbar()) {
         const bool wasLastScrollBar = mev.scrollbar() == m_lastScrollbarUnderMouse.get();
         HitTestRequest request(HitTestRequest::ReadOnly | HitTestRequest::Active);
         mev = m_frame->document()->prepareMouseEvent(request, documentPoint, mouseEvent);
         if (wasLastScrollBar && mev.scrollbar() != m_lastScrollbarUnderMouse.get())
             m_lastScrollbarUnderMouse = 0;
     }
@@ skipping 1881 matching lines @@
     }
 
     return defaultPrevented;
 }
 
 
 
 #endif
 
 }