ToStringAsFixed returns now 0 instead of -0.

runtime/vm/double_conversion.cc

Index: runtime/vm/double_conversion.cc
diff --git a/runtime/vm/double_conversion.cc b/runtime/vm/double_conversion.cc
index ae9d82e7246364c023daa51a9a51d5ac84ac8592..41cec22002d9df43d1da768f9391c86c30901a9e 100644
--- a/runtime/vm/double_conversion.cc
+++ b/runtime/vm/double_conversion.cc
@@ -55,8 +55,9 @@ bool DoubleToStringAsFixed(double d, int fraction_digits, String& result) {
   // The boundaries are exclusive.
   static const double kLowerBoundary = -1e21;
   static const double kUpperBoundary = 1e21;
+  // TODO(floitsch): remove the UNIQUE_ZERO flag when the test is updated.
   static const int kConversionFlags =
-      double_conversion::DoubleToStringConverter::NO_FLAGS;
+      double_conversion::DoubleToStringConverter::UNIQUE_ZERO;
   const int kBufferSize = 128;
   // The output contains the sign, at most kMaxDigitsBeforePoint digits,
   // the decimal point followed by at most fraction_digits digits plus the \0.