Add missing synchronized(mLock) into Autofill onServiceDied

This is an internal fix to avoid merge conflict for AOSP change. The
developer change is aosp/1607953

Bug: 185728458
Test: manual

Change-Id: Ic16ed5e4ac507f02e56f9e9cd94d4b4cfb028d69

services/autofill/java/com/android/server/autofill/Session.java

@@ -1311,7 +1311,9 @@ final class Session implements RemoteFillService.FillServiceCallbacks, ViewState
     @Override
     public void onServiceDied(@NonNull RemoteFillService service) {
         Slog.w(TAG, "removing session because service died");
-        forceRemoveFromServiceLocked();
+        synchronized (mLock) {
+            forceRemoveFromServiceLocked();
+        }
     }
 
     // AutoFillUiCallback