Actually fix build.

src/conversions.h

Index: src/conversions.h
diff --git a/src/conversions.h b/src/conversions.h
index d9326e679715a88eee88a463f45c1c8231c01ecb..1fbb5f11821864320cc95843ccfd41bd89c705c2 100644
--- a/src/conversions.h
+++ b/src/conversions.h
@@ -29,7 +29,6 @@
 #define V8_CONVERSIONS_H_
 
 #include "utils.h"
-#include "double.h"
 
 namespace v8 {
 namespace internal {
@@ -53,11 +52,6 @@ inline bool isDigit(int x, int radix) {
 }
 
 
-inline double SignedZero(bool negative) {
-  return negative ? BitCast<double, uint64_t>(Double::kSignMask) : 0.0;
-}
-
-
 // The fast double-to-(unsigned-)int conversion routine does not guarantee
 // rounding towards zero.
 // For NaN and values outside the int range, return INT_MIN or INT_MAX.