Update PushEvent and PushMessageData to match the spec.

Source/modules/push_messaging/PushMessageData.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef PushMessageData_h
 #define PushMessageData_h
 
 #include "bindings/core/v8/ScriptValue.h"
 #include "bindings/core/v8/ScriptWrappable.h"
 #include "modules/ModulesExport.h"
 #include "platform/heap/Handle.h"
+#include "wtf/Vector.h"
 #include "wtf/text/WTFString.h"
 
 namespace blink {
 
+class ArrayBufferOrArrayBufferViewOrUSVString;
 class Blob;
 class DOMArrayBuffer;
 class ExceptionState;
 class ScriptState;
 
 class MODULES_EXPORT PushMessageData final : public GarbageCollectedFinalized<PushMessageData>, public ScriptWrappable {
     DEFINE_WRAPPERTYPEINFO();
 
 public:
     static PushMessageData* create()
     {
         return new PushMessageData();
     }
-
-    static PushMessageData* create(const String& messageData)
-    {
-        return new PushMessageData(messageData);
-    }
+    static PushMessageData* create(const String& data);
+    static PushMessageData* create(const ArrayBufferOrArrayBufferViewOrUSVString& data);
 
     virtual ~PushMessageData();
 
     PassRefPtr<DOMArrayBuffer> arrayBuffer() const;
     Blob* blob() const;
     ScriptValue json(ScriptState*, ExceptionState&) const;
-    const String& text() const;
+    String text() const;
 
     DECLARE_TRACE();
 
 private:
     PushMessageData();
-    explicit PushMessageData(const String& messageData);
+    PushMessageData(const char* data, unsigned bytesSize);
 
-    String m_messageData;
+    Vector<char> m_data;
 };
 
 } // namespace blink
 
 #endif // PushMessageData_h