Implement the logic to find the correct <link> for Manifest in Document.

Source/core/testing/Internals.h

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  * Copyright (C) 2013 Apple Inc. 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 35 matching lines @@
 class ClientRectList;
 class DOMPoint;
 class DOMStringList;
 class DOMWindow;
 class Document;
 class DocumentMarker;
 class Element;
 class ExceptionState;
 class ExecutionContext;
 class GCObservation;
+class HTMLLinkElement;
 class HTMLMediaElement;
 class InternalProfilers;
 class InternalRuntimeFlags;
 class InternalSettings;
 class LayerRectList;
 class LocalFrame;
 class MallocStatistics;
 class Node;
 class Page;
 class PagePopupController;
@@ skipping 248 matching lines @@
     ScriptPromise createResolvedPromise(ExecutionContext*, ScriptValue);
     ScriptPromise createRejectedPromise(ExecutionContext*, ScriptValue);
     ScriptPromise addOneToPromise(ExecutionContext*, ScriptPromise);
 
     void trace(Visitor*);
 
     void setValueForUser(Element*, const String&);
 
     String textSurroundingNode(Node*, int x, int y, unsigned long maxLength);
 
+    HTMLLinkElement* linkManifest(Document*, ExceptionState&);
+
 private:
     explicit Internals(Document*);
     Document* contextDocument() const;
     LocalFrame* frame() const;
     Vector<String> iconURLs(Document*, int iconTypesMask) const;
     PassRefPtrWillBeRawPtr<ClientRectList> annotatedRegions(Document*, bool draggable, ExceptionState&);
 
     DocumentMarker* markerAt(Node*, const String& markerType, unsigned index, ExceptionState&);
     RefPtrWillBeMember<InternalRuntimeFlags> m_runtimeFlags;
     RefPtrWillBeMember<InternalProfilers> m_profilers;
 };
 
 } // namespace WebCore
 
 #endif