Fix wheel event dispatch logic to fallback to document when hit-test fails

Source/core/input/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 1707 matching lines @@
         return false;
 
     RefPtrWillBeRawPtr<FrameView> protector(m_frame->view());
 
     FrameView* view = m_frame->view();
     if (!view)
         return false;
 
     LayoutPoint vPoint = view->rootFrameToContents(event.position());
 
-    HitTestRequest request(HitTestRequest::ReadOnly);
+    // Pass Active to ensure that hit-test result in current document if otherwise empty
+    // TODO(majidvp): Avoid using Active to trigger hit-testing fallback. See http://crbug.com/505825
+    HitTestRequest request(HitTestRequest::ReadOnly | HitTestRequest::Active);

[Rick Byers, 2015/06/30 20:14:49]

I assume you've done a search to verify that this won't trigger other intended 
side effects inside hit testing somewhere, right?

HitTestRequest::Move would be less of a lie if that part of the hack would work
just as well for you (Active really means a mouse button is down).

[majidvp, 2015/06/30 22:48:32]

Yes I have. It shouldn't have any other side effects when used in combination
with ReadOnly. 
The only other effect of Active is to update hover and active state but that
does not kicked in when ReadOnly is present. This is why "ReadOnly | Active" is
used for this in few other places without causing side-effects.

Move may also work but additionally it requires the point to be in the frame
visible area rect. This should be fine for any user input generated events but
may be problematic for script generated events. I have a test case
specifically for mouse events that are outside visible frame rect which fails
when Move is used.

[Rick Byers, 2015/07/01 13:41:03]

Alright, good enough for a temporary hack.  Thanks!

     HitTestResult result(request, vPoint);
     doc->layoutView()->hitTest(result);
 
     Node* node = result.innerNode();
     // Wheel events should not dispatch to text nodes.
     if (node && node->isTextNode())
         node = ComposedTreeTraversal::parent(*node);
 
     bool isOverWidget;
     if (event.useLatchedEventNode()) {
@@ skipping 2022 matching lines @@
 unsigned EventHandler::accessKeyModifiers()
 {
 #if OS(MACOSX)
     return PlatformEvent::CtrlKey | PlatformEvent::AltKey;
 #else
     return PlatformEvent::AltKey;
 #endif
 }
 
 } // namespace blink