Fix sky include guards to match Chromium style

sky/engine/wtf/dtoa/diy-fp.h

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-#ifndef DOUBLE_CONVERSION_DIY_FP_H_
-#define DOUBLE_CONVERSION_DIY_FP_H_
+#ifndef SKY_ENGINE_WTF_DTOA_DIY-FP_H_
+#define SKY_ENGINE_WTF_DTOA_DIY-FP_H_
 
 #include "sky/engine/wtf/dtoa/utils.h"
 
 namespace WTF {
 
 namespace double_conversion {
 
     // This "Do It Yourself Floating Point" class implements a floating-point number
     // with a uint64 significand and an int exponent. Normalized DiyFp numbers will
     // have the most significant bit of the significand set.
@@ skipping 72 matching lines @@
         static const uint64_t kUint64MSB = UINT64_2PART_C(0x80000000, 00000000);
 
         uint64_t f_;
         int e_;
     };
 
 }  // namespace double_conversion
 
 } // namespace WTF
 
-#endif  // DOUBLE_CONVERSION_DIY_FP_H_
+#endif  // SKY_ENGINE_WTF_DTOA_DIY-FP_H_