Add ClassDeclaration/ClassTypeAlias.isAbstract() and use them.

editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/internal/verifier/ErrorVerifier.java

 /*
  * Copyright (c) 2013, the Dart project authors.
  * 
  * Licensed under the Eclipse Public License v1.0 (the "License"); you may not use this file except
  * in compliance with the License. You may obtain a copy of the License at
  * 
  * http://www.eclipse.org/legal/epl-v10.html
  * 
  * Unless required by applicable law or agreed to in writing, software distributed under the License
  * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
@@ skipping 5363 matching lines @@
   }
 
   /**
    * This verifies that if the given class declaration implements the class Function that it has a
    * concrete implementation of the call method.
    * 
    * @return {@code true} if and only if an error code is generated on the passed node
    * @see StaticWarningCode#FUNCTION_WITHOUT_CALL
    */
   private boolean checkImplementsFunctionWithoutCall(ClassDeclaration node) {
-    if (node.getAbstractKeyword() != null) {
+    if (node.isAbstract()) {
       return false;
     }
     ClassElement classElement = node.getElement();
     if (classElement == null) {
       return false;
     }
     if (!classElement.getType().isSubtypeOf(typeProvider.getFunctionType())) {
       return false;
     }
     // If there is a noSuchMethod method, then don't report the warning, see dartbug.com/16078
@@ skipping 529 matching lines @@
     InterfaceType[] interfaceTypes = classElt.getInterfaces();
     for (InterfaceType interfaceType : interfaceTypes) {
       if (safeCheckForRecursiveInterfaceInheritance(interfaceType.getElement(), path)) {
         return true;
       }
     }
     path.remove(path.size() - 1);
     return false;
   }
 }