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

pkg/compiler/lib/src/script.dart

 // Copyright (c) 2011, 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 dart2js;
 
 class Script {
   final SourceFile file;
 
   /**
    * The readable URI from which this script was loaded.
    *
    * See [LibraryLoader] for terminology on URIs.
    */
   final Uri readableUri;
 
 
   /**
    * The resource URI from which this script was loaded.
    *
    * See [LibraryLoader] for terminology on URIs.
    */
   final Uri resourceUri;
 
   Script(this.readableUri, this.resourceUri, this.file);
 
   String get text => (file == null) ? null : file.slowText();
   String get name => (file == null) ? null : file.filename;
 }