dart2js cps: Use definitions by default, not references.

pkg/compiler/lib/src/cps_ir/loop_hierarchy.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.loop_hierarchy;
 
 import 'cps_ir_nodes.dart';
 import 'cps_fragment.dart';
 
 /// Determines the effective nesting of loops.
@@ skipping 100 matching lines @@
         for (Continuation cont in node.continuations) {
           _processContinuation(cont, catchLoop);
         }
       } else if (node is LetHandler) {
         catchLoop = _processContinuation(node.handler, catchLoop);
       }
     }
     Continuation target;
     if (node is InvokeContinuation) {
       if (node.isRecursive) {
-        target = node.continuation.definition;
+        target = node.continuation;
       } else {
-        target = loopTarget[node.continuation.definition];
+        target = loopTarget[node.continuation];
       }
     } else if (node is Branch) {
       target = _markInnerLoop(
-          loopTarget[node.trueContinuation.definition],
-          loopTarget[node.falseContinuation.definition]);
+          loopTarget[node.trueContinuation],
+          loopTarget[node.falseContinuation]);
     } else if (node == null) {
       // If the code ends abruptly, use the exit loop provided in [update].
       target = _exitLoop;
     } else {
       assert(node is Unreachable || node is Throw || node == null);
     }
     return _markInnerLoop(target, catchLoop);
   }
 
   /// Returns the the innermost loop that effectively encloses both
@@ skipping 29 matching lines @@
   void update(CpsFragment fragment,
               {Continuation exitLoop,
                Continuation catchLoop}) {
     if (fragment.isEmpty) return;
     _exitLoop = exitLoop;
     _currentDepth = getDepth(exitLoop);
     _processBlock(fragment.root, catchLoop);
     _exitLoop = null;
   }
 }