Roll Observatory packages and add a roll script

packages/which/test/test.dart

Index: packages/which/test/test.dart
diff --git a/packages/which/test/test.dart b/packages/which/test/test.dart
new file mode 100755
index 0000000000000000000000000000000000000000..c7bdd92b5d22da38bb3bb52c9df90bf91831129f
--- /dev/null
+++ b/packages/which/test/test.dart
@@ -0,0 +1,16 @@
+
+library which.test;
+
+import 'candidate_paths_test.dart' as candidate_paths;
+import 'has_permission_test.dart' as has_permission;
+import 'is_executable_test.dart' as is_exe;
+import 'which_test.dart' as which;
+import 'which_impl_test.dart' as which_impl;
+
+main() {
+  candidate_paths.main();
+  has_permission.main();
+  is_exe.main();
+  which.main();
+  which_impl.main();
+}