Push version 2.5.7 to trunk....

src/dtoa.h

 // Copyright 2010 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 14 matching lines @@
 // (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 V8_DTOA_H_
 #define V8_DTOA_H_
 
 namespace v8 {
 namespace internal {
 
 enum DtoaMode {
-  // 0.9999999999999999 becomes 0.1
+  // Return the shortest correct representation.
+  // For example the output of 0.299999999999999988897 is (the less accurate but
+  // correct) 0.3.
   DTOA_SHORTEST,
-  // Fixed number of digits after the decimal point.
+  // Return a fixed number of digits after the decimal point.
   // For instance fixed(0.1, 4) becomes 0.1000
   // If the input number is big, the output will be big.
   DTOA_FIXED,
-  // Fixed number of digits (independent of the decimal point).
+  // Return a fixed number of digits, no matter what the exponent is.
   DTOA_PRECISION
 };
 
 // The maximal length of digits a double can have in base 10.
 // Note that DoubleToAscii null-terminates its input. So the given buffer should
 // be at least kBase10MaximalLength + 1 characters long.
 static const int kBase10MaximalLength = 17;
 
 // Converts the given double 'v' to ascii.
 // The result should be interpreted as buffer * 10^(point-length).
@@ skipping 13 matching lines @@
 //   Halfway cases are rounded towards +/-Infinity (away from 0). The call
 //   toFixed(0.15, 2) thus returns buffer="2", point=0.
 //   The returned buffer may contain digits that would be truncated from the
 //   shortest representation of the input.
 //  - PRECISION: produces 'requested_digits' where the first digit is not '0'.
 //   Even though the length of produced digits usually equals
 //   'requested_digits', the function is allowed to return fewer digits, in
 //   which case the caller has to fill the missing digits with '0's.
 //   Halfway cases are again rounded away from 0.
 // 'DoubleToAscii' expects the given buffer to be big enough to hold all digits
-// and a terminating null-character.
-bool DoubleToAscii(double v, DtoaMode mode, int requested_digits,
+// and a terminating null-character. In SHORTEST-mode it expects a buffer of
+// at least kBase10MaximalLength + 1. Otherwise, the size of the output is
+// limited to requested_digits digits plus the null terminator.
+void DoubleToAscii(double v, DtoaMode mode, int requested_digits,
                    Vector<char> buffer, int* sign, int* length, int* point);
 
 } }  // namespace v8::internal
 
 #endif  // V8_DTOA_H_