Remove unused IsNan function

src/double.h

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 112 matching lines @@
     return (d64 & kExponentMask) == 0;
   }
 
   // We consider denormals not to be special.
   // Hence only Infinity and NaN are special.
   bool IsSpecial() const {
     uint64_t d64 = AsUint64();
     return (d64 & kExponentMask) == kExponentMask;
   }
 
-  bool IsNan() const {
-    uint64_t d64 = AsUint64();
-    return ((d64 & kExponentMask) == kExponentMask) &&
-        ((d64 & kSignificandMask) != 0);
-  }
-
   bool IsInfinite() const {
     uint64_t d64 = AsUint64();
     return ((d64 & kExponentMask) == kExponentMask) &&
         ((d64 & kSignificandMask) == 0);
   }
 
   int Sign() const {
     uint64_t d64 = AsUint64();
     return (d64 & kSignMask) == 0? 1: -1;
   }
@@ skipping 80 matching lines @@
       biased_exponent = static_cast<uint64_t>(exponent + kExponentBias);
     }
     return (significand & kSignificandMask) |
         (biased_exponent << kPhysicalSignificandSize);
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_DOUBLE_H_