GitLab

In FindPreviousFocusableViewImpl, in the recursive call to visit the
sibling node, preserves can_go_up, rather than forcing it to true.

Added FocusTraversalNonFocusableTest (test the pathological case
outlined in the bug report).

Also fixed existing comment in test file describing the view hierarchy
to match reality.

BUG=453699
BUG=438425
BUG=451140

Review URL: https://codereview.chromium.org/886033002

Cr-Commit-Position: refs/heads/master@{#314285}