Revert of chromeos: Remove some IME methods from ash::SystemTrayDelegate

Revert of chromeos: Remove some IME methods from ash::SystemTrayDelegate (patchset #5 id:80001 of https://codereview.chromium.org/2891263002/ )

Reason for revert:
I'm going to take a different approach to the IME methods in the system tray delegate. There's a design doc linked from the bug.


Original issue's description:
> chromeos: Remove some IME methods from ash::SystemTrayDelegate
> 
> For the mustash project we're trying to eliminate delegates that call
> from ash back into chrome browser.
> 
> The IME InputMethodManager interfaces live in //ui/base/ime/chromeos, and
> //ash already uses them, so convert some of the system tray code to use
> InputMethodManager directly.
> 
> * Remove InputMethodSwitchRecorder and move histogram recording to //ash
> * Use InputMethodManager directly in the ash keyboard accelerator code
> * Remove ash::ImeControlDelegate and chrome's ImeController.
> * Use MockInputMethodManager in all AcceleratorControllerTests
> 
> BUG=724305
> TEST=ash_unittests, manually switch IMEs when running chrome
> 
> Review-Url: https://codereview.chromium.org/2891263002
> Cr-Commit-Position: refs/heads/master@{#474380}
> Committed: https://chromium.googlesource.com/chromium/src/+/1290776535cfda1fa1cd7867d5a2ae2ded7e92ec

TBR=azurewei@chromium.org,shuchen@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=724305

[James Cook, 2017-06-05 20:03:39]

Created Revert of chromeos: Remove some IME methods from ash::SystemTrayDelegate

[James Cook, 2017-06-05 20:05:52]

On 2017/06/05 20:03:39, James Cook wrote:
> Created Revert of chromeos: Remove some IME methods from
ash::SystemTrayDelegate

Abandoned. I'll revert this by hand because I want to keep parts of the CL.