dart2js cps: Use definitions by default, not references.

pkg/compiler/lib/src/cps_ir/gvn.dart

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library dart2js.cps_ir.gvn;
 
 import 'cps_ir_nodes.dart';
 import '../universe/side_effects.dart';
 import '../elements/elements.dart';
 import 'optimizers.dart' show Pass;
@@ skipping 385 matching lines @@
       });
     } else {
       effectNumbers = effectsAt[cont];
       assert(effectNumbers != null);
     }
 
     return cont.body;
   }
 
   void visitInvokeContinuation(InvokeContinuation node) {
-    Continuation cont = node.continuation.definition;
+    Continuation cont = node.continuation;
     if (cont.isRecursive) return;
     EffectNumbers join = effectsAt[cont];
     if (join == null) {
       effectsAt[cont] = effectNumbers.copy();
     } else {
       join.join(effectNumberer, effectNumbers);
     }
   }
 
   void visitBranch(Branch node) {
-    Continuation trueCont = node.trueContinuation.definition;
-    Continuation falseCont = node.falseContinuation.definition;
+    Continuation trueCont = node.trueContinuation;
+    Continuation falseCont = node.falseContinuation;
     // Copy the effect number vector once, so the analysis of one branch does
     // not influence the other.
     effectsAt[trueCont] = effectNumbers;
     effectsAt[falseCont] = effectNumbers.copy();
   }
 }
 
 /// Maps vectors to numbers, such that two vectors with the same contents
 /// map to the same number.
 class GvnTable {
@@ skipping 180 matching lines @@
 
   @override
   processReference(Reference ref) {
     callback(ref);
   }
 
   static void forEach(Primitive node, ReferenceCallback callback) {
     new InputVisitor(callback).visit(node);
   }
 }