js_ast: Avoid precedence issue with negative numbers as receivers at calls

tests/compiler/dart2js/js_constant_test.dart

 // Copyright (c) 2015, 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.
 
 import 'dart:async';
 import 'package:async_helper/async_helper.dart';
 import 'package:expect/expect.dart';
 import 'compiler_helper.dart';
 
 const String TEST_1 = r"""
   import 'dart:_foreign_helper';
   main() {
-    // present: 'Moose'
-    JS('', 'Moose');
-
-    // absent: 'Phantom' - pure.
-    JS('returns: bool;effects:none;depends:none;throws:never', 'Phantom');
-
-    // present: 'Spider' - unused after constant folding 'is', but unpure.
-    print(JS('returns:bool;effects:none;depends:all', 'Spider') is bool);
-
-    // absent: 'Wasp' - unused after constant folding 'is', and unpure.
-    print(JS('returns:bool;effects:none;depends:all;throws:never', 'Wasp')
-          is bool);
-
-    JS('', 'Array');   // absent: "Array"
+    JS('', '#.toString()', -5);
+    // absent: "5.toString"
+    // present: "(-5).toString"
   }
 """;
 
-const String TEST_2 = r"""
-  import 'dart:_foreign_helper';
-  main() {
-    var w1 = JS('returns:int;depends:none;effects:none;throws:never',
-        'foo(#)', 1);
-    var w2 = JS('returns:int;depends:none;effects:none;throws:never',
-        'foo(#)', 2);
-
-    print([w2, w1]);
-
-    // present: '[foo(2), foo(1)]' - since 'foo' is pure, we expect to generate
-    // code out-of-order.
-  }
-""";
-
-const String TEST_3 = r"""
-  import 'dart:_foreign_helper';
-  main() {
-    var s = JS('String|Null', '"Hello"');
-    var s1 = JS('returns:String;depends:none;effects:none;throws:null(1)',
-        '#.toLowerCase()', s);
-    var s2 = JS('returns:String;depends:none;effects:none;throws:null(1)',
-        '#.toUpperCase()', s);
-    print(s2);
-
-    // absent: 'toLowerCase' - removed since s.toUpperCase() generates the same
-    // noSuchMethod.
-  }
-""";
-
 
 main() {
   RegExp directivePattern = new RegExp(
       //      \1                    \2        \3
       r'''// *(present|absent): (?:"([^"]*)"|'([^'']*)')''',
       multiLine: true);
 
   Future check(String test) {
     Uri uri = new Uri(scheme: 'dart', path: 'test');
     var compiler = compilerFor(test, uri, expectedErrors: 0);
@@ skipping 12 matching lines @@
           assert(directive == 'absent');
           Expect.isFalse(generated.contains(pattern),
               "Must not find '$pattern' in:\n$generated");
         }
       }
     });
   }
 
   asyncTest(() => Future.wait([
     check(TEST_1),
-    check(TEST_2),
-    check(TEST_3),
   ]));
 }