Make CredentialsContainer#get argument options optional to match the spec

third_party/WebKit/LayoutTests/http/tests/credentialmanager/credentialscontainer-get-basics.html

Index: third_party/WebKit/LayoutTests/http/tests/credentialmanager/credentialscontainer-get-basics.html
diff --git a/third_party/WebKit/LayoutTests/http/tests/credentialmanager/credentialscontainer-get-basics.html b/third_party/WebKit/LayoutTests/http/tests/credentialmanager/credentialscontainer-get-basics.html
index 0270a9f4c782d7102ce01a2e252c2f2a4e79c4ef..a4531acd1c997aef56405d5d123eb48a2a2f0e08 100644
--- a/third_party/WebKit/LayoutTests/http/tests/credentialmanager/credentialscontainer-get-basics.html
+++ b/third_party/WebKit/LayoutTests/http/tests/credentialmanager/credentialscontainer-get-basics.html
@@ -19,11 +19,11 @@ add_completion_callback(() => {
 });
 
 (function() {
-    var t = async_test("navigator.credentials.get() (no argument) should throw.");
+    var t = async_test("navigator.credentials.get() with no argument.");
     t.step(function () {
         navigator.credentials.get().then(
-            t.unreached_func(),
-            t.step_func_done());
+            t.step_func(stubResolverUndefinedChecker.bind(t)),
+            t.step_func(stubRejectionChecker.bind(t)));
     });
 }());