Move dart2js from sdk/lib/_internal/compiler to pkg/compiler

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 372 matching lines @@
     }
   }
 
   visitContinuation(cps_ir.Continuation c) {
     var old_node = current_block;
     current_block = getBlock(c);
     visit(c.body);
     current_block = old_node;
   }
 }