IDL: Generate union type containers

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.
  *
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 namespace blink {
 
 class AnimationTimeline;
 class AXObjectCache;
 class Attr;
 class CDATASection;
 class CSSStyleDeclaration;
 class CSSStyleSheet;
 class CanvasRenderingContext2D;
+class CanvasRenderingContext2DOrWebGLRenderingContext;
 class Chrome;
 class Comment;
 class ConsoleMessage;
 class ContextFeatures;
 class CustomElementMicrotaskRunQueue;
 class CustomElementRegistrationContext;
 class DOMImplementation;
 class DocumentFragment;
 class DocumentLifecycleNotifier;
 class DocumentLoader;
@@ skipping 757 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, RefPtrWillBeRawPtr<CanvasRenderingContext2D>&, RefPtrWillBeRawPtr<WebGLRenderingContext>&);
+    void getCSSCanvasContext(const String& type, const String& name, int width, int height, CanvasRenderingContext2DOrWebGLRenderingContext&);
     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 556 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