As a component of allowing arbitrary CCs, we must allow for the Esc key
to be pressed to clear autocomplete suggestions. The default behavior of
gr-autocomplete is to emit a 'cancel' event when Esc is pressed.
This change modifies the behavior of the autocomplete to emit 'cancel'
only when suggestions are empty. The new workflow is to tap Esc once to
clear suggestions, and again to emit the cancel event.
Feature: Issue 5832
Change-Id: I53d4f1485c2e6c013a957f09413c149ae219d2e4
6336284679