Fix sky include guards to match Chromium style

sky/engine/wtf/text/WTFString.h

Index: sky/engine/wtf/text/WTFString.h
diff --git a/sky/engine/wtf/text/WTFString.h b/sky/engine/wtf/text/WTFString.h
index 71484c4856fa9be73c9515fd941bf9357443ffc0..d229837b3f0312c95768400546e3ac6abd167611 100644
--- a/sky/engine/wtf/text/WTFString.h
+++ b/sky/engine/wtf/text/WTFString.h
@@ -19,8 +19,8 @@
  *
  */
 
-#ifndef WTFString_h
-#define WTFString_h
+#ifndef SKY_ENGINE_WTF_TEXT_WTFSTRING_H_
+#define SKY_ENGINE_WTF_TEXT_WTFSTRING_H_
 
 // This file would be called String.h, but that conflicts with <string.h>
 // on systems without case-sensitive file systems.
@@ -686,4 +686,4 @@ using WTF::isSpaceOrNewline;
 using WTF::reverseFind;
 
 #include "sky/engine/wtf/text/AtomicString.h"
-#endif // WTFString_h
+#endif  // SKY_ENGINE_WTF_TEXT_WTFSTRING_H_