GitLab

This CL:
- Fixes EventConverterEvdev::SetAllowedKeys() to block disallowed keys
- Dispatches a synthetic key release event for any blocked pressed keys when
  EventConverterEvdev::SetAllowedKeys() is called instead of waiting till the
  user releases the key.

BUG=465611
TEST=EventConverterEvdevImplTest.*

Review URL: https://codereview.chromium.org/992323004

Cr-Commit-Position: refs/heads/master@{#320170}