Fix event passing to overlay scrollbars when over a plugin

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 1253 matching lines @@
             m_resizeScrollableArea = layer->scrollableArea();
             m_resizeScrollableArea->setInResizeMode(true);
             m_offsetFromResizeCorner = m_resizeScrollableArea->offsetFromResizeCorner(p);
             invalidateClick();
             return true;
         }
     }
 
     m_frame->selection().setCaretBlinkingSuspended(true);
 
+    FrameView* view = m_frame->view();
+    Scrollbar* scrollbar = view ? view->scrollbarAtPoint(mouseEvent.position()) : 0;

[Rick Byers, 2014/05/22 13:53:36]

Shouldn't this already be in mev.scrollbar()?  Seems wrong to hit test this
special case again when we already have a HitTestResults here.

+    if (scrollbar) {
+        updateLastScrollbarUnderMouse(scrollbar, true);
+        if (passMousePressEventToScrollbar(mev, scrollbar))
+            return true;
+    }
+
     bool swallowEvent = !dispatchMouseEvent(EventTypeNames::mousedown, mev.targetNode(), m_clickCount, mouseEvent, true);
     swallowEvent = swallowEvent || !handleMouseFocus(mouseEvent);
     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 | HitTestRequest::ConfusingAndOftenMisusedDisallowShadowContent);
         mev = m_frame->document()->prepareMouseEvent(request, documentPoint, mouseEvent);
         if (wasLastScrollBar && mev.scrollbar() != m_lastScrollbarUnderMouse.get())
             m_lastScrollbarUnderMouse = nullptr;
     }
 
     if (swallowEvent) {
         // scrollbars should get events anyway, even disabled controls might be scrollable
-        Scrollbar* scrollbar = mev.scrollbar();
+        scrollbar = mev.scrollbar();
 
         updateLastScrollbarUnderMouse(scrollbar, true);
 
         if (scrollbar)
             passMousePressEventToScrollbar(mev, scrollbar);
     } else {
         if (shouldRefetchEventTarget(mev)) {
             HitTestRequest request(HitTestRequest::ReadOnly | HitTestRequest::Active | HitTestRequest::ConfusingAndOftenMisusedDisallowShadowContent);
             mev = m_frame->document()->prepareMouseEvent(request, documentPoint, mouseEvent);
         }
 
-        FrameView* view = m_frame->view();
-        Scrollbar* scrollbar = view ? view->scrollbarAtPoint(mouseEvent.position()) : 0;
-        if (!scrollbar)
-            scrollbar = mev.scrollbar();
+        scrollbar = mev.scrollbar();
 
         updateLastScrollbarUnderMouse(scrollbar, true);
 
         if (scrollbar && passMousePressEventToScrollbar(mev, scrollbar))
             swallowEvent = true;
         else
             swallowEvent = handleMousePressEvent(mev);
     }
 
     return swallowEvent;
@@ skipping 2413 matching lines @@
 unsigned EventHandler::accessKeyModifiers()
 {
 #if OS(MACOSX)
     return PlatformEvent::CtrlKey | PlatformEvent::AltKey;
 #else
     return PlatformEvent::AltKey;
 #endif
 }
 
 } // namespace WebCore