Use new library/import syntax in dart2js.

sdk/lib/_internal/compiler/implementation/source_map_builder.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_map_builder');
+library source_map_builder;
 
-#import('dart:json');
+import 'dart:json';
 
-#import('scanner/scannerlib.dart');
-#import('source_file.dart');
+import 'scanner/scannerlib.dart';
+import 'source_file.dart';
 
 class SourceMapBuilder {
   static const int VLQ_BASE_SHIFT = 5;
   static const int VLQ_BASE_MASK = (1 << 5) - 1;
   static const int VLQ_CONTINUATION_BIT = 1 << 5;
   static const int VLQ_CONTINUATION_MASK = 1 << 5;
   static const String BASE64_DIGITS = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmn'
                                       'opqrstuvwxyz0123456789+/';
 
   List<SourceMapEntry> entries;
@@ skipping 146 matching lines @@
 
   int getColumn() => sourceFile.getColumn(getLine(), token.charOffset);
 
   String getSourceName() {
     if (token.isIdentifier()) return token.slowToString();
     return null;
   }
 
   bool isValid() => token.charOffset < sourceFile.text.length;
 }