[credentialsmanager] Remove redundant tests

third_party/WebKit/LayoutTests/http/tests/credentialmanager/federatedcredential-basics.html

Index: third_party/WebKit/LayoutTests/http/tests/credentialmanager/federatedcredential-basics.html
diff --git a/third_party/WebKit/LayoutTests/http/tests/credentialmanager/federatedcredential-basics.html b/third_party/WebKit/LayoutTests/http/tests/credentialmanager/federatedcredential-basics.html
index a1771598a1e7bac8904af95c3a9eace38cea7bea..6754999c164e54899ceebe301df21b668ea3da05 100644
--- a/third_party/WebKit/LayoutTests/http/tests/credentialmanager/federatedcredential-basics.html
+++ b/third_party/WebKit/LayoutTests/http/tests/credentialmanager/federatedcredential-basics.html
@@ -2,7 +2,6 @@
 <title>Credential Manager: FederatedCredential basics.</title>
 <script src="../resources/testharness.js"></script>
 <script src="../resources/testharnessreport.js"></script>
-<script src="resources/interfaces.js"></script>
 <script>
 test(function() {
     var credential = new FederatedCredential({
@@ -12,17 +11,6 @@ test(function() {
         'iconURL': 'https://example.test/icon.png'
     });
 
-    assert_true(credential instanceof Credential);
-    assert_true(credential instanceof FederatedCredential);
-
-    verify_interface('FederatedCredential', credential, {
-        id: 'string',
-        name: 'string',
-        iconURL: 'string',
-        provider: 'string',
-        type: 'string'
-    });
-
     assert_equals(credential.id, 'id');
     assert_equals(credential.name, 'name');
     assert_equals(credential.iconURL, 'https://example.test/icon.png');