Fix 23563: double unary- operator unstable for NANs

runtime/lib/double.dart

Index: runtime/lib/double.dart
diff --git a/runtime/lib/double.dart b/runtime/lib/double.dart
index 95f026da931a9b59c3bfdd8f53a1c53869e8d8b4..280bf3b4a470ec0d8a898c2c4ce684c4a2eb2e01 100644
--- a/runtime/lib/double.dart
+++ b/runtime/lib/double.dart
@@ -47,12 +47,11 @@ class _Double extends _Num implements double {
   }
   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;
-    }
-    return 0.0 - this;
+    // Handles properly 0.0, NAN, and other doubles.
+    return this._flipSignBit;
   }
+  double get _flipSignBit native "Double_flipSignBit";
+
   bool operator ==(other) {
     if (!(other is num)) return false;
     return _equal(other.toDouble());