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

editor/tools/plugins/com.google.dart.engine_test/src/com/google/dart/engine/ast/ClassDeclarationTest.java

Index: editor/tools/plugins/com.google.dart.engine_test/src/com/google/dart/engine/ast/ClassDeclarationTest.java
diff --git a/editor/tools/plugins/com.google.dart.engine_test/src/com/google/dart/engine/ast/ClassDeclarationTest.java b/editor/tools/plugins/com.google.dart.engine_test/src/com/google/dart/engine/ast/ClassDeclarationTest.java
index 74779433c2254e87817dc03276e695f001970f1f..6f15500d58c2b1f8ebedff9debff0b395f68fdf3 100644
--- a/editor/tools/plugins/com.google.dart.engine_test/src/com/google/dart/engine/ast/ClassDeclarationTest.java
+++ b/editor/tools/plugins/com.google.dart.engine_test/src/com/google/dart/engine/ast/ClassDeclarationTest.java
@@ -14,6 +14,7 @@
 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;
@@ -106,4 +107,9 @@ public class ClassDeclarationTest extends ParserTestCase {
     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());
+  }
 }