Fix sky include guards to match Chromium style

sky/engine/wtf/dtoa/strtod.h

Index: sky/engine/wtf/dtoa/strtod.h
diff --git a/sky/engine/wtf/dtoa/strtod.h b/sky/engine/wtf/dtoa/strtod.h
index b9d794b88c504e2dba07d6c9b71512dcfeea5305..4aa3b1c4f39c3fc68603a7f01e09666cef1061f6 100644
--- a/sky/engine/wtf/dtoa/strtod.h
+++ b/sky/engine/wtf/dtoa/strtod.h
@@ -25,8 +25,8 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-#ifndef DOUBLE_CONVERSION_STRTOD_H_
-#define DOUBLE_CONVERSION_STRTOD_H_
+#ifndef SKY_ENGINE_WTF_DTOA_STRTOD_H_
+#define SKY_ENGINE_WTF_DTOA_STRTOD_H_
 
 #include "sky/engine/wtf/dtoa/utils.h"
 
@@ -42,4 +42,4 @@ namespace double_conversion {
 
 } // namespace WTF
 
-#endif  // DOUBLE_CONVERSION_STRTOD_H_
+#endif  // SKY_ENGINE_WTF_DTOA_STRTOD_H_