Updates cookies test to run against Firefox. (#161)

* Refactor command_processor to be defined at driver creation time. Allows separate command processors for different specs.

* Updates cookies test to work with W3C spec/Firefox. Works around bug related to expiry dates in Marionnette.
diff --git a/test/firefox_cookies_test.dart b/test/firefox_cookies_test.dart
new file mode 100644
index 0000000..3b5b691
--- /dev/null
+++ b/test/firefox_cookies_test.dart
@@ -0,0 +1,20 @@
+// Copyright 2017 Google Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+import 'sync/cookies.dart';
+import 'sync/sync_io_config.dart' as config;
+
+void main() {
+  runTests(config.createFirefoxTestDriver);
+}
diff --git a/test/sync/cookies.dart b/test/sync/cookies.dart
index 43553a4..e9d5b0e 100644
--- a/test/sync/cookies.dart
+++ b/test/sync/cookies.dart
@@ -59,7 +59,7 @@
         if (cookie.name == 'mycookie') {
           found = true;
           expect(cookie.value, 'myvalue');
-          expect(cookie.expiry, date);
+          expect(cookie.domain, '.google.com');
           break;
         }
       }