Ignore abort operation for clank

This CL changes the behavior of cancel() as a no-op because the request
cannot be cancelled once sent to gmscore since gmscore does not support
request cancellation yet.

Bug: 999095
Change-Id: I8d6172386191534855ddbd374555c13e088b2561
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1777050Reviewed-by: David Trainor <dtrainor@chromium.org>
Commit-Queue: Suzy Li <suzyli@google.com>
Cr-Commit-Position: refs/heads/master@{#692155}

chrome/android/java/src/org/chromium/chrome/browser/webauth/AuthenticatorImpl.java

@@ -111,7 +111,7 @@ public class AuthenticatorImpl extends HandlerResponseCallback implements Authen
 
     @Override
     public void cancel() {
-        onError(AuthenticatorStatus.NOT_IMPLEMENTED);
+        // Not implemented, ignored because request sent to gmscore fido cannot be cancelled.
         return;
     }