Make CredentialsContainer#get argument options optional to match the spec

third_party/WebKit/Source/modules/credentialmanager/CredentialsContainer.idl

Index: third_party/WebKit/Source/modules/credentialmanager/CredentialsContainer.idl
diff --git a/third_party/WebKit/Source/modules/credentialmanager/CredentialsContainer.idl b/third_party/WebKit/Source/modules/credentialmanager/CredentialsContainer.idl
index 7e3cefe86d20755ef1bf0ad36fa71d57627be9e0..f96c6710fe43852c6a90aee20b9ef51954a4c14e 100644
--- a/third_party/WebKit/Source/modules/credentialmanager/CredentialsContainer.idl
+++ b/third_party/WebKit/Source/modules/credentialmanager/CredentialsContainer.idl
@@ -2,10 +2,12 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// https://w3c.github.io/webappsec-credential-management/#credentialscontainer
+
 [
     RuntimeEnabled=CredentialManager,
 ] interface CredentialsContainer {
-    [CallWith=ScriptState, MeasureAs=CredentialManagerGet] Promise get(CredentialRequestOptions options);
+    [CallWith=ScriptState, MeasureAs=CredentialManagerGet] Promise get(optional CredentialRequestOptions options);
     [CallWith=ScriptState, MeasureAs=CredentialManagerStore] Promise store(Credential credential);
     [CallWith=ScriptState, MeasureAs=CredentialManagerRequireUserMediation] Promise requireUserMediation();
 };