[oilpan] Completely move HTMLFormControlElement's hierarchy to the managed heap

Source/core/rendering/RenderTextControlSingleLine.cpp

 /**
  * Copyright (C) 2006, 2007, 2010 Apple Inc. All rights reserved.
  *           (C) 2008 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/) 
  * Copyright (C) 2010 Google Inc. All rights reserved.
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies).
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
@@ skipping 457 matching lines @@
 }
 
 bool RenderTextControlSingleLine::logicalScroll(ScrollLogicalDirection direction, ScrollGranularity granularity, float multiplier, Node** stopNode)
 {
     RenderLayer* layer = innerTextElement()->renderBox()->layer();
     if (layer && layer->scroll(logicalToPhysical(direction, style()->isHorizontalWritingMode(), style()->isFlippedBlocksWritingMode()), granularity, multiplier))
         return true;
     return RenderBlock::logicalScroll(direction, granularity, multiplier, stopNode);
 }
 
-HTMLInputElement* RenderTextControlSingleLine::inputElement() const
+Result<HTMLInputElement> RenderTextControlSingleLine::inputElement() const
 {
     return node()->toInputElement();
 }
 
 }