Fix sky include guards to match Chromium style

sky/engine/wtf/dtoa/double.h

Index: sky/engine/wtf/dtoa/double.h
diff --git a/sky/engine/wtf/dtoa/double.h b/sky/engine/wtf/dtoa/double.h
index d0f449d20f0669586ef7c5ea48918b9223cde83c..92ac041218717e0af1b5ac9a06aad221f4b4bacf 100644
--- a/sky/engine/wtf/dtoa/double.h
+++ b/sky/engine/wtf/dtoa/double.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_DOUBLE_H_
-#define DOUBLE_CONVERSION_DOUBLE_H_
+#ifndef SKY_ENGINE_WTF_DTOA_DOUBLE_H_
+#define SKY_ENGINE_WTF_DTOA_DOUBLE_H_
 
 #include "diy-fp.h"
 
@@ -246,4 +246,4 @@ namespace double_conversion {
 
 } // namespace WTF
 
-#endif  // DOUBLE_CONVERSION_DOUBLE_H_
+#endif  // SKY_ENGINE_WTF_DTOA_DOUBLE_H_