Add --packages flag when compiling dart2js snapshot

utils/compiler/create_snapshot.dart

 // Copyright (c) 2013, 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.
 
 import 'dart:io';
 
 Future<String> getVersion(var rootPath) {
   var suffix = Platform.operatingSystem == 'windows' ? '.exe' : '';
   var printVersionScript = rootPath.resolve("tools/print_version.py");
   return Process.run("python$suffix",
@@ skipping 45 matching lines @@
 
 void writeSnapshotFile(var path, var content) {
     File file = new File(path);
     var writer = file.openSync(mode: FileMode.WRITE);
     writer.writeStringSync(content);
     writer.close();
 }
 
 Future createSnapshot(var dart_file) {
   return Process.run(Platform.executable,
-                     ["--snapshot=$dart_file.snapshot",
+                     ["--packages=../../.packages",
+                      "--snapshot=$dart_file.snapshot",
                       dart_file])
       .then((result) {
         if (result.exitCode != 0) {
           print("Could not generate snapshot: result code ${result.exitCode}");
           print(result.stdout);
           print(result.stderr);
           throw "Could not generate snapshot";
         }
       });
 }
@@ skipping 26 matching lines @@
     createSnapshot(wrapper);
   });
 
   getDart2jsSnapshotGenerationFile(args, rootPath).then((result) {
     var wrapper = "${args['output_dir']}/dart2js.dart";
     writeSnapshotFile(wrapper, result);
     createSnapshot(wrapper);
   });
 
 }