IDL: Use Nullable for union type return value

Source/core/dom/Document.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2008, 2009, 2011, 2012 Google Inc. All rights reserved.
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) Research In Motion Limited 2010-2011. All rights reserved.
@@ skipping 4930 matching lines @@
     m_ranges.add(range);
 }
 
 void Document::detachRange(Range* range)
 {
     // We don't ASSERT m_ranges.contains(range) to allow us to call this
     // unconditionally to fix: https://bugs.webkit.org/show_bug.cgi?id=26044
     m_ranges.remove(range);
 }
 
-void Document::getCSSCanvasContext(const String& type, const String& name, int width, int height, bool& is2d, RefPtrWillBeRawPtr<CanvasRenderingContext2D>& context2d, bool& is3d, RefPtrWillBeRawPtr<WebGLRenderingContext>& context3d)
+void Document::getCSSCanvasContext(const String& type, const String& name, int width, int height, Nullable<RefPtrWillBeRawPtr<CanvasRenderingContext2D> >& context2d, Nullable<RefPtrWillBeRawPtr<WebGLRenderingContext> >& context3d)
 {
     HTMLCanvasElement& element = getCSSCanvasElement(name);
     element.setSize(IntSize(width, height));
     CanvasRenderingContext* context = element.getContext(type);
     if (!context)
         return;
 
     if (context->is2d()) {
-        is2d = true;
-        context2d = toCanvasRenderingContext2D(context);
+        context2d.set(toCanvasRenderingContext2D(context));
     } else if (context->is3d()) {
-        is3d = true;
-        context3d = toWebGLRenderingContext(context);
+        context3d.set(toWebGLRenderingContext(context));
     }
 }
 
 HTMLCanvasElement& Document::getCSSCanvasElement(const String& name)
 {
     RefPtrWillBeMember<HTMLCanvasElement>& element = m_cssCanvasElements.add(name, nullptr).storedValue->value;
     if (!element) {
         element = HTMLCanvasElement::create(*this);
         element->setAccelerationDisabled(true);
     }
@@ skipping 908 matching lines @@
 using namespace blink;
 void showLiveDocumentInstances()
 {
     WeakDocumentSet& set = liveDocumentSet();
     fprintf(stderr, "There are %u documents currently alive:\n", set.size());
     for (WeakDocumentSet::const_iterator it = set.begin(); it != set.end(); ++it) {
         fprintf(stderr, "- Document %p URL: %s\n", *it, (*it)->url().string().utf8().data());
     }
 }
 #endif