Change assert implementation to not depend on a top-level function called 'assert'.

lib/compiler/implementation/lib/js_helper.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.
 
 #library('dart:_js_helper');
 
 #import('coreimpl.dart');
 
 #source('constant_map.dart');
 #source('native_helper.dart');
@@ skipping 793 matching lines @@
     if (message is String) {
       if (message.endsWith('is null') ||
           message.endsWith('is undefined') ||
           message.endsWith('is null or undefined')) {
         return new NullPointerException();
       } else if (message.contains(' is not a function') ||
                  (ieErrorCode == 438 && ieFacilityNumber == 10)) {
         // Examples:
         //  x.foo is not a function
         //  'undefined' is not a function (evaluating 'x.foo(1,2,3)')
-        // Object doesn't support property or method 'foo' which sets the error 
+        // Object doesn't support property or method 'foo' which sets the error
         // code 438 in IE.
         // TODO(kasperl): Compute the right name if possible.
         return new NoSuchMethodException('', '<unknown>', []);
       }
     }
 
     // If we cannot determine what kind of error this is, we fall back
     // to reporting this as a generic exception. It's probably better
     // than nothing.
     return new Exception(message is String ? message : '');
@@ skipping 356 matching lines @@
 
 /**
  * Special interface recognized by the compiler and implemented by DOM
  * objects that support integer indexing. This interface is not
  * visible to anyone, and is only injected into special libraries.
  */
 interface JavaScriptIndexingBehavior {
 }
 
 /**
+ * Helper function for implementing asserts. The compiler treats this specially.
+ */
+void assert(condition) {
+  if (condition is Function) condition = condition();
+  if (!condition) throw new AssertionError();
+}
+
+/**
  * Called by generated code when a method that must be statically
  * resolved cannot be found.
  */
 void throwNoSuchMethod(obj, name, arguments) {
   throw new NoSuchMethodException(obj, name, arguments);
 }