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..3692b1c5d812718ad9db584bc509b73f4452c768 100644
--- a/runtime/lib/double.dart
+++ b/runtime/lib/double.dart
@@ -51,8 +51,13 @@ class _Double extends _Num implements double {
       // -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());