Oilpan: fix build after r355906.

third_party/WebKit/Source/core/html/HTMLCanvasElement.cpp

 /*
  * Copyright (C) 2004, 2006, 2007 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Alp Toker <alp@atoker.com>
  * Copyright (C) 2010 Torch Mobile (Beijing) Co. Ltd. All rights reserved.
  *
  * 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 735 matching lines @@
 }
 
 void HTMLCanvasElement::notifySurfaceInvalid()
 {
     if (m_context && m_context->is2d())
         m_context->loseContext(CanvasRenderingContext::RealLostContext);
 }
 
 DEFINE_TRACE(HTMLCanvasElement)
 {
-#if ENABLE(OILPAN)
-    visitor->trace(m_observers);
     visitor->trace(m_context);
-#endif
     DocumentVisibilityObserver::trace(visitor);
     HTMLElement::trace(visitor);
 }
 
 void HTMLCanvasElement::updateExternallyAllocatedMemory() const
 {
     int bufferCount = 0;
     if (m_imageBuffer) {
         bufferCount++;
         if (m_imageBuffer->isAccelerated()) {
@@ skipping 176 matching lines @@
 {
     return FloatSize(width(), height());
 }
 
 bool HTMLCanvasElement::isOpaque() const
 {
     return m_context && !m_context->hasAlpha();
 }
 
 } // blink