Remove support for operator negate and replace occurrences with unary

runtime/lib/double.dart

 // Copyright (c) 2011, 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 implements double {
   factory Double.fromInteger(int value)
       native "Double_doubleFromInteger";
   int hashCode() {
     try {
       return toInt();
@@ skipping 29 matching lines @@
   double operator %(num other) {
     return modulo_(other.toDouble());
   }
   double modulo_(double other) native "Double_modulo";
 
   double remainder(num other) {
     return remainder_(other.toDouble());
   }
   double remainder_(double other) native "Double_remainder";
 
-  double operator negate() {
+  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;
   }
   bool operator ==(other) {
     if (!(other is num)) return false;
     return equal_(other.toDouble());
   }
@@ skipping 161 matching lines @@
         return EQUAL;
       }
     } else if (isNaN()) {
       return other.isNaN() ? EQUAL : GREATER;
     } else {
       // Other is NaN.
       return LESS;
     }
   }
 }