mash-cleanup: Move ime_controller mojo interface to C++ instead.

This will make the code a lot simpler.

We will follow up with a CL that removes the 'caching' code within
ime_controller since the interface is no longer async.

Bug: 1023574
Change-Id: I995ae92d9f8ba9c4de557744443fc44f93ba7de7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1923871
Auto-Submit: Darren Shen <[email protected]>
Reviewed-by: Oliver Chang <[email protected]>
Reviewed-by: Scott Violet <[email protected]>
Commit-Queue: Darren Shen <[email protected]>
Cr-Commit-Position: refs/heads/master@{#723240}
61 files changed