Add support for the package: directive in Frog and dart2js.

frog/reader.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.
 
 /**
  * An code reader that abstracts away the distinction between internal and user
  * libraries.
  */
 class LibraryReader {
   Map _specialLibs;
@@ skipping 25 matching lines @@
         'dart:isolate': joinPaths(options.libDir, 'isolate/isolate_frog.dart'),
         'dart:json': joinPaths(options.libDir, 'json/json_frog.dart'),
         'dart:uri': joinPaths(options.libDir, 'uri/uri.dart'),
         'dart:utf': joinPaths(options.libDir, 'utf/utf.dart'),
       };
     } else {
       world.error('Invalid configuration ${options.config}');
     }
   }
 
   SourceFile readFile(String fullname) {

[Bob Nystrom, 2012/04/09 23:54:08]

Should be "fullName".

[nweiz, 2012/04/10 00:16:31]

Done.

-    var filename = _specialLibs[fullname];
+    String filename;
+    if (fullname.startsWith('package:')) {
+      filename = joinPaths(dirname(options.dartScript),
+          joinPaths('packages', fullname.substring('package:'.length)));
+    } else {
+      filename = _specialLibs[fullname];
+    }
+
     if (filename == null) {
       filename = fullname;
     }
 
     if (world.files.fileExists(filename)) {
       // TODO(jimhug): Should we cache these based on time stamps here?
       return new SourceFile(filename, world.files.readAll(filename));
     } else {
       world.error('File not found: $filename', null);
       return new SourceFile(filename, '');
     }
   }
 }