Update pub to use new import syntax.

utils/pub/sdk_source.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('sdk_source');
+library sdk_source;
 
-#import('io.dart');
-#import('package.dart');
-#import('pubspec.dart');
-#import('source.dart');
-#import('version.dart');
+import 'io.dart';
+import 'package.dart';
+import 'pubspec.dart';
+import 'source.dart';
+import 'version.dart';
 
 /// A package source that uses libraries from the Dart SDK.
 class SdkSource extends Source {
   final String name = "sdk";
   final bool shouldCache = false;
 
   /// The root directory of the Dart SDK.
   final String _rootDir;
 
   String get rootDir {
@@ skipping 42 matching lines @@
       if (found) return new Future<String>.immediate(pkgPath);
 
       // Not in "pkg", so try "lib".
       // TODO(rnystrom): Get rid of this when all SDK packages are moved from
       // "lib" to "pkg".
       var libPath = join(rootDir, "lib", id.description);
       return exists(libPath).transform((found) => found ? libPath : null);
     });
   }
 }