Fix 23563: double unary- operator unstable for NANs

runtime/lib/double.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 class _Double extends _Num implements double {
   factory _Double.fromInteger(int value)
       native "Double_doubleFromInteger";
 
   Type get runtimeType => double;
 
@@ skipping 33 matching lines @@
 
   double remainder(num other) {
     return _remainder(other.toDouble());
   }
   double _remainder(double other) native "Double_remainder";
   double operator -() {
     if (this == 0.0) {
       // -0.0 is canonicalized by the VM's parser, therefore no cycles.
       return isNegative ? 0.0 : -0.0;
     }
+    if (this.isNaN) {
+      return this._flipNANsign;
+    }
     return 0.0 - this;
   }
+  double get _flipNANsign native "Double_flipNANsign";
+
   bool operator ==(other) {
     if (!(other is num)) return false;
     return _equal(other.toDouble());
   }
   bool _equal(double other)native "Double_equal";
   bool _equalToInteger(int other) native "Double_equalToInteger";
   bool operator <(num other) {
     return other > this;
   }
   bool operator >(num other) {
@@ skipping 198 matching lines @@
         return EQUAL;
       }
     } else if (isNaN) {
       return other.isNaN ? EQUAL : GREATER;
     } else {
       // Other is NaN.
       return LESS;
     }
   }
 }