Add a small JS parser to ease the building of ASTs

sdk/lib/_internal/compiler/implementation/js_backend/constant_emitter.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.
 
 part of js_backend;
 
 class ConstantEmitter  {
   ConstantReferenceEmitter _referenceEmitter;
   ConstantInitializerEmitter _initializerEmitter;
 
@@ skipping 80 matching lines @@
     } else if (value == -double.INFINITY) {
       return new jsAst.LiteralNumber("(-1/0)");
     } else {
       return new jsAst.LiteralNumber("$value");
     }
   }
 
   jsAst.Expression visitTrue(TrueConstant constant) {
     if (compiler.enableMinification) {
       // Use !0 for true.
-      return new jsAst.Prefix("!", new jsAst.LiteralNumber("0"));
+      return js["!0"];
     } else {
       return new jsAst.LiteralBool(true);
     }
-
   }
 
   jsAst.Expression visitFalse(FalseConstant constant) {
     if (compiler.enableMinification) {
       // Use !1 for false.
-      return new jsAst.Prefix("!", new jsAst.LiteralNumber("1"));
+      return js["!1"];
     } else {
       return new jsAst.LiteralBool(false);
     }
   }
 
   /**
    * Write the contents of the quoted string to a [CodeBuffer] in
    * a form that is valid as JavaScript string literal content.
    * The string is assumed quoted by double quote characters.
    */
@@ skipping 193 matching lines @@
   }
 
   List<jsAst.Expression> _array(List<Constant> values) {
     List<jsAst.Expression> valueList = <jsAst.Expression>[];
     for (int i = 0; i < values.length; i++) {
       valueList.add(_reference(values[i]));
     }
     return valueList;
   }
 }