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

lib/compiler/implementation/elements/elements.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('elements');
 
 #import('dart:uri');
 
 #import('../tree/tree.dart');
 #import('../scanner/scannerlib.dart');
@@ skipping 140 matching lines @@
       kind === ElementKind.GENERATIVE_CONSTRUCTOR_BODY;
   bool isCompilationUnit() => kind === ElementKind.COMPILATION_UNIT;
   bool isClass() => kind === ElementKind.CLASS;
   bool isPrefix() => kind === ElementKind.PREFIX;
   bool isVariable() => kind === ElementKind.VARIABLE;
   bool isParameter() => kind === ElementKind.PARAMETER;
   bool isStatement() => kind === ElementKind.STATEMENT;
   bool isTypedef() => kind === ElementKind.TYPEDEF;
   bool isTypeVariable() => kind === ElementKind.TYPE_VARIABLE;
   bool isField() => kind === ElementKind.FIELD;
+  bool isAbstractField() => kind === ElementKind.ABSTRACT_FIELD;
   bool isGetter() => kind === ElementKind.GETTER;
   bool isSetter() => kind === ElementKind.SETTER;
   bool isAccessor() => isGetter() || isSetter();
   bool isForeign() => kind === ElementKind.FOREIGN;
   bool isLibrary() => kind === ElementKind.LIBRARY;
   bool impliesType() => (kind.category & ElementCategory.IMPLIES_TYPE) != 0;
   bool isExtendable() => (kind.category & ElementCategory.IS_EXTENDABLE) != 0;
 
   /** See [ErroneousElement] for documentation. */
   bool isErroneous() => false;
@@ skipping 1481 matching lines @@
 
   MetadataAnnotation ensureResolved(Compiler compiler) {
     if (resolutionState == STATE_NOT_STARTED) {
       compiler.resolver.resolveMetadataAnnotation(this);
     }
     return this;
   }
 
   String toString() => 'MetadataAnnotation($value, $resolutionState)';
 }