A few more fixes for testing in the repo.

test/test_pub.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.
 
 /// Test infrastructure for testing pub.
 ///
 /// Unlike typical unit tests, most pub tests are integration tests that stage
 /// some stuff on the file system, run pub, and then validate the results. This
 /// library provides an API to build tests like that.
 library test_pub;
@@ skipping 555 matching lines @@
   var versionPath = p.join(pubRoot, '.pub', 'pub.version');
   if (fileExists(hashPath) && fileExists(versionPath)) {
     var oldHash = readTextFile(hashPath);
     var oldVersion = readTextFile(versionPath);
 
     if (oldHash == hash && oldVersion == version && fileExists(snapshotPath)) {
       return;
     }
   }
 
-  var dartSnapshot = runProcessSync(Platform.executable, [
-    '--snapshot=$snapshotPath',
-    p.join(pubRoot, 'bin', 'pub.dart')
-  ]);
+  var args = ['--snapshot=$snapshotPath'];
+  if (Platform.packageRoot.isNotEmpty) {
+    args.add('--package-root=${Platform.packageRoot}');
+  }
+  args.add(p.join(pubRoot, 'bin', 'pub.dart'));
+
+  var dartSnapshot = runProcessSync(Platform.executable, args);
   if (dartSnapshot.exitCode != 0) throw "Failed to run dart --snapshot.";
 
   writeTextFile(hashPath, hash);
   writeTextFile(versionPath, version);
 }
 
 /// Returns a hash that encapsulates the current state of the repo.
 String _hashChanges() {
   var hash = new SHA1();
 
@@ skipping 456 matching lines @@
         _lastMatcher.matches(item.last, matchState);
   }
 
   Description describe(Description description) {
     return description.addAll("(", ", ", ")", [_firstMatcher, _lastMatcher]);
   }
 }
 
 /// A [StreamMatcher] that matches multiple lines of output.
 StreamMatcher emitsLines(String output) => inOrder(output.split("\n"));