Handle modifiers (abstract) on class nodes.

lib/compiler/implementation/scanner/listener.dart

Index: lib/compiler/implementation/scanner/listener.dart
diff --git a/lib/compiler/implementation/scanner/listener.dart b/lib/compiler/implementation/scanner/listener.dart
index 3298428766a661c10ad6f2cbe62d4ec997f1dd80..5c5d00e245621ca8841ea0d5bf77a80c1fe213a0 100644
--- a/lib/compiler/implementation/scanner/listener.dart
+++ b/lib/compiler/implementation/scanner/listener.dart
@@ -1071,8 +1071,10 @@ class NodeListener extends ElementListener {
     TypeAnnotation supertype = popNode();
     NodeList typeParameters = popNode();
     Identifier name = popNode();
-    pushNode(new ClassNode(name, typeParameters, supertype, interfaces, null,
-                           beginToken, extendsKeyword, body, endToken));
+    Modifiers modifiers = popNode();
+    pushNode(new ClassNode(modifiers, name, typeParameters, supertype,
+                           interfaces, null, beginToken, extendsKeyword, body,
+                           endToken));
   }
 
   void endFunctionTypeAlias(Token typedefKeyword, Token endToken) {
@@ -1092,7 +1094,7 @@ class NodeListener extends ElementListener {
                                        null, ',');
     NodeList typeParameters = popNode();
     Identifier name = popNode();
-    pushNode(new ClassNode(name, typeParameters, null, supertypes,
+    pushNode(new ClassNode(null, name, typeParameters, null, supertypes,
                            defaultClause, interfaceKeyword, null, body,
                            endToken));
   }