Fix sky include guards to match Chromium style

sky/engine/public/platform/WebBlendMode.h

Index: sky/engine/public/platform/WebBlendMode.h
diff --git a/sky/engine/public/platform/WebBlendMode.h b/sky/engine/public/platform/WebBlendMode.h
index 76b71449288b4c9a58eedeffbd2f993ed5207dcf..530557f24081ccbd87be91089fc37e7ebe271a83 100644
--- a/sky/engine/public/platform/WebBlendMode.h
+++ b/sky/engine/public/platform/WebBlendMode.h
@@ -28,8 +28,8 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
-#ifndef WebBlendMode_h
-#define WebBlendMode_h
+#ifndef SKY_ENGINE_PUBLIC_PLATFORM_WEBBLENDMODE_H_
+#define SKY_ENGINE_PUBLIC_PLATFORM_WEBBLENDMODE_H_
 
 #include "sky/engine/public/platform/WebCommon.h"
 
@@ -56,4 +56,4 @@ enum WebBlendMode {
 
 } // namespace blink
 
-#endif
+#endif  // SKY_ENGINE_PUBLIC_PLATFORM_WEBBLENDMODE_H_