child user: Show error state on ParentAccessView

Error state is shown after unsuccessful access code validation
and cleared when user changes input (deletes or updates input
field content).

Backspace behavior was updated accordingly. Pressing backspace
when input field has text deletes the text but does not move
focus to the previous field. Pressing backspace on empty input
field moves focus to the previous field.

Bug: 911326
Test: ParentAccessViewTest
Change-Id: I2860c0d02dee6f7aba95fcdaaa3271b98a25c07c
Reviewed-on: https://chromium-review.googlesource.com/c/1477878
Commit-Queue: Aga Wronska <agawronska@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Reviewed-by: Michael Giuffrida <michaelpg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#635751}
5 files changed