Chrome Version       : 72 (current trunk)

What steps will reproduce the problem?
1. Load https://rsolomakhin.github.io/autofill/
2. Put a breakpoint in NewPasswordFormManager::Fill
3. Type into the password field

What is the expected result?
The breakpoint should not be hit.

What happens instead of that?
The breakpoint is hit, through the posted task inside ProcessMatches.

The NPFM where the breakpoint is hit is the cloned NPFM which is used for the saving fallback. It has a null driver_ and cannot fill anywhere.

We should probably just abort Fill() on a null driver_. As it is, this causes some confusing calls, such as to NewPasswordFormManager::RecordMetricOnCompareParsingResult (see also bug 910121).