IssueTracker

Artifact used: com.android.support:recyclerview-v7:27.1.1
Version used: 27.1.1
Theme used: N/A
Devices/Android versions reproduced on: Any

Regarding the check at the top of `submitList` here: https://android.googlesource.com/platform/frameworks/support/+/9e9830fc8a4fd710b3c3b9c21253f8b31ce32ea2/recyclerview/src/main/java/androidx/recyclerview/widget/AsyncListDiffer.java#214
```
if (newList == mList) {
    // nothing to do
    return;
}
```

There's a race condition -- suppose we have lists A and B, and the differ's `mList` before starting is list A.
1. Submit list B - async diff generation N kicks off
2. Submit list A - `newList` matches `mList` since diff gen N hasn't completed yet, but `mMaxScheduledGeneration` is not incremented and this returns early
3. Async diff gen N is accepted, despite list A being submitted after list B.

Seems this could be fixed by incrementing `mMaxScheduledGeneration`. As a workaround, I am wrapping my lists in a new identity before submitting them to the differ.