Revert "Implement override checks."

lib/compiler/implementation/tree/nodes.dart

Index: lib/compiler/implementation/tree/nodes.dart
diff --git a/lib/compiler/implementation/tree/nodes.dart b/lib/compiler/implementation/tree/nodes.dart
index 4c86235772d4eb3f5a70e8eec204ca0e3d19d59d..fa36ce4cddb9e200eb68fc175d4c662a8f5fed9c 100644
--- a/lib/compiler/implementation/tree/nodes.dart
+++ b/lib/compiler/implementation/tree/nodes.dart
@@ -1075,12 +1075,11 @@ class Modifiers extends Node {
   static final int FLAG_CONST = FLAG_VAR << 1;
   static final int FLAG_FACTORY = FLAG_CONST << 1;
 
-  Modifiers(NodeList nodes) : this.withFlags(nodes, computeFlags(nodes.nodes));
+  Modifiers(NodeList nodes)
+    : this.nodes = nodes, flags = computeFlags(nodes.nodes);
 
   Modifiers.empty() : this(new NodeList.empty());
 
-  Modifiers.withFlags(this.nodes, this.flags);
-
   static int computeFlags(Link<Node> nodes) {
     int flags = 0;
     for (; !nodes.isEmpty(); nodes = nodes.tail) {
@@ -1108,19 +1107,6 @@ class Modifiers extends Node {
   bool isVar() => (flags & FLAG_VAR) != 0;
   bool isConst() => (flags & FLAG_CONST) != 0;
   bool isFactory() => (flags & FLAG_FACTORY) != 0;
-
-  String toString() {
-    LinkBuilder<String> builder = new LinkBuilder<String>();
-    if (isStatic()) builder.addLast('static');
-    if (isAbstract()) builder.addLast('abstract');
-    if (isFinal()) builder.addLast('final');
-    if (isVar()) builder.addLast('var');
-    if (isConst()) builder.addLast('const');
-    if (isFactory()) builder.addLast('factory');
-    StringBuffer buffer = new StringBuffer();
-    builder.toLink().printOn(buffer, ', ');
-    return buffer.toString();
-  }
 }
 
 class StringInterpolation extends StringNode {