Merge pull request #15976 from RudyLu/keyboard/Bug963377-keyboard_covers_value_selector

Bug 963377 - [B2G][Keyboard] Keyboard blocks "cancel" / "ok" options, r=timdream(cherry picked from commit 1aa8e778a0368e98eb1b5d534285a47c29068951)
Merge pull request #16028 from RudyLu/keyboard/Bug968729-add_unit_test

Bug 968729 - Add unit test for Bug 963377.
r=timdream(cherry picked from commit 3fc26ae786e3869a7ef1e23afc9807ac1b4741f2)
a=test-only

Conflicts:
	build/jshint/xfail.list