Bug 985331 - [Keyboard UX update][User Story] Long press spacebar to
dismiss keyboard.
 - Remove the swipe-to-dimiss feature and tutorial screen.
 - Add integration test for keyboard dimiss.
Merge pull request #18741 from RudyLu/keyboard/Bug985331-longpress_dismiss_keyboard

Bug 985331 - [Keyboard UX update][User Story] Long press spacebar to
r=timdream.