Fix sky include guards to match Chromium style

sky/engine/wtf/dtoa/cached-powers.h

 // Copyright 2010 the V8 project authors. All rights reserved.
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-#ifndef DOUBLE_CONVERSION_CACHED_POWERS_H_
-#define DOUBLE_CONVERSION_CACHED_POWERS_H_
+#ifndef SKY_ENGINE_WTF_DTOA_CACHED-POWERS_H_
+#define SKY_ENGINE_WTF_DTOA_CACHED-POWERS_H_
 
 #include "diy-fp.h"
 
 namespace WTF {
 
 namespace double_conversion {
 
     class PowersOfTenCache {
     public:
 
@@ skipping 17 matching lines @@
         //   kMinDecimalExponent <= requested_exponent, and
         //   requested_exponent < kMaxDecimalExponent + kDecimalExponentDistance.
         static void GetCachedPowerForDecimalExponent(int requested_exponent,
                                                      DiyFp* power,
                                                      int* found_exponent);
     };
 }  // namespace double_conversion
 
 } // namespace WTF
 
-#endif  // DOUBLE_CONVERSION_CACHED_POWERS_H_
+#endif  // SKY_ENGINE_WTF_DTOA_CACHED-POWERS_H_