Fix sky include guards to match Chromium style

sky/engine/core/dom/custom/CustomElementObserver.h

 /*
  * Copyright (C) 2013 Google 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.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 10 matching lines @@
  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
-#ifndef CustomElementObserver_h
-#define CustomElementObserver_h
+#ifndef SKY_ENGINE_CORE_DOM_CUSTOM_CUSTOMELEMENTOBSERVER_H_
+#define SKY_ENGINE_CORE_DOM_CUSTOM_CUSTOMELEMENTOBSERVER_H_
 
 #include "sky/engine/platform/heap/Handle.h"
 #include "sky/engine/wtf/HashMap.h"
 
 namespace blink {
 
 class Element;
 
 class CustomElementObserver {
 public:
     virtual ~CustomElementObserver() { }
 
     // API for CustomElement to kick off notifications
 
     static void notifyElementDidFinishParsingChildren(Element*);
     static void notifyElementWasDestroyed(Element*);
 
 protected:
     CustomElementObserver() { }
 
     void observe(Element*);
     void unobserve(Element*);
 
     virtual void elementDidFinishParsingChildren(Element*) = 0;
     virtual void elementWasDestroyed(Element* element) { unobserve(element); }
 };
 
 }
 
-#endif // CustomElementObserver_h
+#endif  // SKY_ENGINE_CORE_DOM_CUSTOM_CUSTOMELEMENTOBSERVER_H_