Fix sky include guards to match Chromium style

sky/engine/wtf/DateMath.h

 /*
  * Copyright (C) 1999-2000 Harri Porten (porten@kde.org)
  * Copyright (C) 2006, 2007 Apple Inc. All rights reserved.
  * Copyright (C) 2009 Google Inc. All rights reserved.
  * Copyright (C) 2010 Research In Motion Limited. All rights reserved.
  *
  * Version: MPL 1.1/GPL 2.0/LGPL 2.1
  *
  * The contents of this file are subject to the Mozilla Public License Version
  * 1.1 (the "License"); you may not use this file except in compliance with
@@ skipping 22 matching lines @@
  * of those above. If you wish to allow use of your version of this file only
  * under the terms of either the GPL or the LGPL, and not to allow others to
  * use your version of this file under the terms of the MPL, indicate your
  * decision by deleting the provisions above and replace them with the notice
  * and other provisions required by the GPL or the LGPL. If you do not delete
  * the provisions above, a recipient may use your version of this file under
  * the terms of any one of the MPL, the GPL or the LGPL.
  *
  */
 
-#ifndef DateMath_h
-#define DateMath_h
+#ifndef SKY_ENGINE_WTF_DATEMATH_H_
+#define SKY_ENGINE_WTF_DATEMATH_H_
 
 #include <stdint.h>
 #include <string.h>
 #include "sky/engine/wtf/WTFExport.h"
 #include "sky/engine/wtf/text/WTFString.h"
 
 namespace WTF {
 
 WTF_EXPORT void initializeDates();
 
@@ skipping 37 matching lines @@
 using WTF::msPerDay;
 using WTF::msPerHour;
 using WTF::msPerMinute;
 using WTF::msPerSecond;
 using WTF::msToYear;
 using WTF::secondsPerMinute;
 using WTF::parseDateFromNullTerminatedCharacters;
 using WTF::makeRFC2822DateString;
 using WTF::convertToLocalTime;
 
-#endif // DateMath_h
+#endif  // SKY_ENGINE_WTF_DATEMATH_H_