IDL: Use Nullable for union type return value

Source/core/dom/Document.h

 /*
  * 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, 2010, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
@@ skipping 11 matching lines @@
  * along with this library; see the file COPYING.LIB.  If not, write to
  * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  * Boston, MA 02110-1301, USA.
  *
  */
 
 #ifndef Document_h
 #define Document_h
 
 #include "bindings/core/v8/ExceptionStatePlaceholder.h"
+#include "bindings/core/v8/Nullable.h"
 #include "bindings/core/v8/ScriptValue.h"
 #include "core/animation/AnimationClock.h"
 #include "core/animation/CompositorPendingAnimations.h"
 #include "core/dom/ContainerNode.h"
 #include "core/dom/DocumentEncodingData.h"
 #include "core/dom/DocumentInit.h"
 #include "core/dom/DocumentLifecycle.h"
 #include "core/dom/DocumentSupplementable.h"
 #include "core/dom/DocumentTiming.h"
 #include "core/dom/ExecutionContext.h"
@@ skipping 789 matching lines @@
     // Returns null if there is no such element.
     HTMLLinkElement* linkManifest() const;
 
     void setUseSecureKeyboardEntryWhenActive(bool);
     bool useSecureKeyboardEntryWhenActive() const;
 
     void updateFocusAppearanceSoon(bool restorePreviousSelection);
     void cancelFocusAppearanceUpdate();
 
     // Extension for manipulating canvas drawing contexts for use in CSS
-    void getCSSCanvasContext(const String& type, const String& name, int width, int height, bool&, RefPtrWillBeRawPtr<CanvasRenderingContext2D>&, bool&, RefPtrWillBeRawPtr<WebGLRenderingContext>&);
+    void getCSSCanvasContext(const String& type, const String& name, int width, int height, Nullable<RefPtrWillBeRawPtr<CanvasRenderingContext2D> >&, Nullable<RefPtrWillBeRawPtr<WebGLRenderingContext> >&);
     HTMLCanvasElement& getCSSCanvasElement(const String& name);
 
     bool isDNSPrefetchEnabled() const { return m_isDNSPrefetchEnabled; }
     void parseDNSPrefetchControlHeader(const String&);
 
     // FIXME(crbug.com/305497): This should be removed once LocalDOMWindow is an ExecutionContext.
     virtual void postTask(PassOwnPtr<ExecutionContextTask>) OVERRIDE; // Executes the task on context's thread asynchronously.
     void postInspectorTask(PassOwnPtr<ExecutionContextTask>);
 
     virtual void tasksWereSuspended() OVERRIDE FINAL;
@@ skipping 569 matching lines @@
 Node* eventTargetNodeForDocument(Document*);
 
 } // namespace blink
 
 #ifndef NDEBUG
 // Outside the WebCore namespace for ease of invocation from gdb.
 void showLiveDocumentInstances();
 #endif
 
 #endif // Document_h