Use new library/import syntax in dart2js.

sdk/lib/_internal/compiler/implementation/source_file.dart

 // Copyright (c) 2012, 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('source_file');
+library source_file;
 
-#import('dart:math');
+import 'dart:math';
 
-#import('colors.dart', prefix: 'colors');
+import 'colors.dart' as colors;
 
 /**
  * Represents a file of source code.
  */
 class SourceFile {
 
   /** The name of the file. */
   final String filename;
 
   /** The text content of the file. */
@@ skipping 76 matching lines @@
       }
 
       for (; i < toColumn; i++) {
         buf.add(color('^'));
       }
     }
 
     return buf.toString();
   }
 }