Revert "Bug 975992 - Keep keyboard2 state in Gecko rather than Gaia"

This reverts commit 5ffd3aefddeb628ff27405e6d07281b108b5dec9.
Merge pull request #16575 from comoyo/revert_new_keyboard_promisify

Revert "Bug 975992 - Keep keyboard2 state in Gecko rather than Gaia"