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

editor/tools/plugins/com.google.dart.engine_test/src/com/google/dart/engine/ast/ClassDeclarationTest.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
  * or implied. See the License for the specific language governing permissions and limitations under
  * the License.
  */
 package com.google.dart.engine.ast;
 
 import com.google.dart.engine.parser.ParserTestCase;
+import com.google.dart.engine.scanner.Keyword;
 
 import static com.google.dart.engine.ast.AstFactory.classDeclaration;
 import static com.google.dart.engine.ast.AstFactory.constructorDeclaration;
 import static com.google.dart.engine.ast.AstFactory.fieldDeclaration;
 import static com.google.dart.engine.ast.AstFactory.formalParameterList;
 import static com.google.dart.engine.ast.AstFactory.identifier;
 import static com.google.dart.engine.ast.AstFactory.methodDeclaration;
 import static com.google.dart.engine.ast.AstFactory.variableDeclaration;
 
 import java.util.ArrayList;
@@ skipping 72 matching lines @@
         null,
         null,
         null,
         null,
         aMethod,
         bMethod);
     assertSame(aMethod, clazz.getMethod("a"));
     assertSame(bMethod, clazz.getMethod("b"));
     assertSame(null, clazz.getMethod("noSuchMethod"));
   }
+
+  public void test_isAbstract() throws Exception {
+    assertFalse(classDeclaration(null, "A", null, null, null, null).isAbstract());
+    assertTrue(classDeclaration(Keyword.ABSTRACT, "B", null, null, null, null).isAbstract());
+  }
 }