dart2js cps: Redundant join elimination.

pkg/compiler/lib/src/cps_ir/cps_ir_tracer.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.ir_tracer;
 
 import 'dart:async' show EventSink;
 import 'cps_ir_nodes.dart' as cps_ir hide Function;
 import '../tracer.dart';
 
@@ skipping 92 matching lines @@
 
   visitLetPrim(cps_ir.LetPrim node) {
     String id = names.name(node.primitive);
     printStmt(id, "LetPrim $id = ${formatPrimitive(node.primitive)}");
     visit(node.body);
   }
 
   visitLetCont(cps_ir.LetCont node) {
     if (IR_TRACE_LET_CONT) {
       String dummy = names.name(node);
-      for (cps_ir.Continuation continuation in node.continuations) {
-        String id = names.name(continuation);
-        printStmt(dummy, "LetCont $id = <$id>");
-      }
+      String ids = node.continuations.map(names.name).join(', ');
+      printStmt(dummy, "LetCont $ids");
     }
     visit(node.body);
   }
 
   visitLetHandler(cps_ir.LetHandler node) {
     if (IR_TRACE_LET_CONT) {
       String dummy = names.name(node);
       String id = names.name(node.handler);
       printStmt(dummy, "LetHandler $id = <$id>");
     }
@@ skipping 534 matching lines @@
     unexpectedNode(node);
   }
 
   @override
   visitForeignCode(cps_ir.ForeignCode node) {
     if (node.continuation != null) {
       addEdgeToContinuation(node.continuation);
     }
   }
 }