Fix sky include guards to match Chromium style

sky/engine/core/css/CSSAspectRatioValue.h

Index: sky/engine/core/css/CSSAspectRatioValue.h
diff --git a/sky/engine/core/css/CSSAspectRatioValue.h b/sky/engine/core/css/CSSAspectRatioValue.h
index 55f2aa544d2e041dd7dfbfd0e8f40db967445a9e..92b3a94ae85d196cb4f69668db94799e85a7ef1e 100644
--- a/sky/engine/core/css/CSSAspectRatioValue.h
+++ b/sky/engine/core/css/CSSAspectRatioValue.h
@@ -26,8 +26,8 @@
  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
-#ifndef CSSAspectRatioValue_h
-#define CSSAspectRatioValue_h
+#ifndef SKY_ENGINE_CORE_CSS_CSSASPECTRATIOVALUE_H_
+#define SKY_ENGINE_CORE_CSS_CSSASPECTRATIOVALUE_H_
 
 #include "sky/engine/core/css/CSSValue.h"
 
@@ -63,4 +63,4 @@ DEFINE_CSS_VALUE_TYPE_CASTS(CSSAspectRatioValue, isAspectRatioValue());
 
 }
 
-#endif
+#endif  // SKY_ENGINE_CORE_CSS_CSSASPECTRATIOVALUE_H_