Revert of [oilpan]: Remove support for tracing off-heap hashmaps.

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 219 matching lines @@
 {
 }
 
 EventHandler::~EventHandler()
 {
     ASSERT(!m_fakeMouseMoveEventTimer.isActive());
 }
 
 void EventHandler::trace(Visitor* visitor)
 {
-#if ENABLE(OILPAN)
     visitor->trace(m_mousePressNode);
     visitor->trace(m_capturingMouseEventsNode);
     visitor->trace(m_nodeUnderMouse);
     visitor->trace(m_lastNodeUnderMouse);
     visitor->trace(m_clickNode);
     visitor->trace(m_dragTarget);
     visitor->trace(m_frameSetBeingResized);
     visitor->trace(m_latchedWheelEventNode);
     visitor->trace(m_previousWheelScrolledNode);
     visitor->trace(m_targetForTouchID);
     visitor->trace(m_touchSequenceDocument);
     visitor->trace(m_scrollGestureHandlingNode);
     visitor->trace(m_previousGestureScrolledNode);
     visitor->trace(m_lastDeferredTapElement);
-#endif
 }
 
 DragState& EventHandler::dragState()
 {
     DEFINE_STATIC_LOCAL(OwnPtrWillBePersistent<DragState>, state, (adoptPtrWillBeNoop(new DragState())));
     return *state;
 }
 
 void EventHandler::clear()
 {
@@ skipping 3556 matching lines @@
 unsigned EventHandler::accessKeyModifiers()
 {
 #if OS(MACOSX)
     return PlatformEvent::CtrlKey | PlatformEvent::AltKey;
 #else
     return PlatformEvent::AltKey;
 #endif
 }
 
 } // namespace blink