Fix sky include guards to match Chromium style

sky/engine/core/css/CSSFunctionValue.h

Index: sky/engine/core/css/CSSFunctionValue.h
diff --git a/sky/engine/core/css/CSSFunctionValue.h b/sky/engine/core/css/CSSFunctionValue.h
index 32bd05461b03d394d7368d6c6aacfa5700a12935..111e91a263774df8026350d5a4297894b5a34b37 100644
--- a/sky/engine/core/css/CSSFunctionValue.h
+++ b/sky/engine/core/css/CSSFunctionValue.h
@@ -23,8 +23,8 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
-#ifndef CSSFunctionValue_h
-#define CSSFunctionValue_h
+#ifndef SKY_ENGINE_CORE_CSS_CSSFUNCTIONVALUE_H_
+#define SKY_ENGINE_CORE_CSS_CSSFUNCTIONVALUE_H_
 
 #include "sky/engine/core/css/CSSValue.h"
 
@@ -56,5 +56,5 @@ DEFINE_CSS_VALUE_TYPE_CASTS(CSSFunctionValue, isFunctionValue());
 
 } // namespace blink
 
-#endif
+#endif  // SKY_ENGINE_CORE_CSS_CSSFUNCTIONVALUE_H_