Don't abort signin in SigninManager after onSystemAccountsChanged

It doesn't make much sense to abort sign-in if some other account was
updated. Moreover, SigninManager doesn't expect sign-in to be aborted at
random moments, so it might be left in an unconsistent state. This cl
removes onSystemAccountsChanged() method altogether as it just calls the
abortSignIn() method inside it.

Bug: 1059422
Change-Id: I1320ca10e93879665493473f2eb74148f30c580b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2094298Reviewed-by: Alice Wang <aliceywang@chromium.org>
Reviewed-by: Boris Sazonov <bsazonov@chromium.org>
Commit-Queue: Tanmoy Mollik <triploblastic@chromium.org>
Cr-Commit-Position: refs/heads/master@{#750933}

chrome/android/java/src/org/chromium/chrome/browser/signin/SigninManager.java

@@ -351,16 +351,6 @@ public class SigninManager
         }
     }
 
-    /**
-    * Clear pending sign in when system accounts in AccountTrackerService were refreshed.
-    */
-    @Override
-    public void onSystemAccountsChanged() {
-        if (mSignInState != null) {
-            abortSignIn();
-        }
-    }
-
     /**
      * Starts the sign-in flow, and executes the callback when finished.
      *