Copy dart2js source into pkg/compiler

pkg/compiler/lib/src/js/template.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.
 
 part of js;
 
 class TemplateManager {
   Map<String, Template> expressionTemplates = new Map<String, Template>();
   Map<String, Template> statementTemplates = new Map<String, Template>();
 
@@ skipping 660 matching lines @@
     if (count != before) containsInterpolatedNode.add(node);
     return null;
   }
 
   visitInterpolatedNode(InterpolatedNode node) {
     interpolatedNodes.add(node);
     containsInterpolatedNode.add(node);
     ++count;
   }
 }