Fix sky include guards to match Chromium style

sky/viewer/content_handler_impl.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 SKY_VIEWER_CONTENT_HANDLER_H_
-#define SKY_VIEWER_CONTENT_HANDLER_H_
+#ifndef SKY_VIEWER_CONTENT_HANDLER_IMPL_H_
+#define SKY_VIEWER_CONTENT_HANDLER_IMPL_H_
 
 #include "base/message_loop/message_loop.h"
 #include "mojo/public/interfaces/application/shell.mojom.h"
 #include "mojo/services/public/interfaces/content_handler/content_handler.mojom.h"
 
 namespace sky {
 class DocumentView;
 
 class ContentHandlerImpl : public mojo::InterfaceImpl<mojo::ContentHandler> {
  public:
   ContentHandlerImpl(scoped_refptr<base::MessageLoopProxy> compositor_thread);
   virtual ~ContentHandlerImpl();
 
  private:
   // Overridden from ContentHandler:
   virtual void StartApplication(mojo::ShellPtr shell,
                                 mojo::URLResponsePtr response) override;
 
   scoped_refptr<base::MessageLoopProxy> compositor_thread_;
 
   DISALLOW_COPY_AND_ASSIGN(ContentHandlerImpl);
 };
 
 }  // namespace sky
 
-#endif  // SKY_VIEWER_DOCUMENT_VIEW_H_
+#endif  // SKY_VIEWER_CONTENT_HANDLER_IMPL_H_