Oilpan: address ScrollableArea-induced build breakage from r194957.

Source/core/frame/FrameHost.cpp

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 86 matching lines @@
 
 ConsoleMessageStorage& FrameHost::consoleMessageStorage() const
 {
     return *m_consoleMessageStorage;
 }
 
 DEFINE_TRACE(FrameHost)
 {
     visitor->trace(m_page);
     visitor->trace(m_topControls);
-    visitor->trace(m_pinchViewport);
     visitor->trace(m_eventHandlerRegistry);
     visitor->trace(m_consoleMessageStorage);
 }
 
 #if ENABLE(ASSERT)
 void checkFrameCountConsistency(int expectedFrameCount, Frame* frame)
 {
     ASSERT(expectedFrameCount >= 0);
 
     int actualFrameCount = 0;
     for (; frame; frame = frame->tree().traverseNext())
         ++actualFrameCount;
 
     ASSERT(expectedFrameCount == actualFrameCount);
 }
 #endif
 
 int FrameHost::subframeCount() const
 {
 #if ENABLE(ASSERT)
     checkFrameCountConsistency(m_subframeCount + 1, m_page->mainFrame());
 #endif
     return m_subframeCount;
 }
 
 }