Fix a bug in dart2js's shrinking reductions.

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

 // Copyright (c) 2014, 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.shrinking_reductions;
 
 import 'cps_ir_nodes.dart';
 import 'optimizers.dart';
 
 /**
@@ skipping 260 matching lines @@
     return false;
   }
 
   if (cont.firstRef.parent is! InvokeContinuation) return false;
 
   InvokeContinuation invoke = cont.firstRef.parent;
   if (cont != invoke.continuation.definition) return false;
 
   // Beta-reduction will move the continuation's body to its unique invocation
   // site.  This is not safe if the body is moved into an exception handler
-  // binding.
+  // binding.  Search from the invocation to the continuation binding to
+  // make sure that there is no binding for a handler.
   Node current = invoke.parent;
   while (current != cont.parent) {
+    // There is no need to reduce a beta-redex inside a deleted subterm.
+    if (current == ShrinkingReducer._DELETED) return false;
     if (current is LetHandler) return false;
     current = current.parent;
   }
   return true;
 }
 
 /// Returns true iff the continuation consists of a continuation
 /// invocation, passing on all parameters. Special cases exist (see below).
 bool _isEtaCont(Continuation cont) {
   if (cont.isReturnContinuation || cont.body is! InvokeContinuation) {
@@ skipping 428 matching lines @@
   }
 
   String toString() => "$kind: $node";
 }
 
 /// A dummy class used solely to mark nodes as deleted once they are removed
 /// from a term.
 class _DeletedNode extends Node {
   accept(_) => null;
 }