Revert of Fix HidService lifetime issues.

Revert of Fix HidService lifetime issues. (patchset #3 of https://codereview.chromium.org/464753002/)

Reason for revert:
Caused build failure: http://build.chromium.org/p/chromium/builders/Linux%20x64/builds/69507/steps/compile/logs/stdio

Original issue's description:
> Fix HidService lifetime issues.
> 
> This reverts HidService to a singleton instance, adding two gross
> and presently hard-to-avoid properties:
> 
> 1. Its instance getter takes a UI message loop proxy
> 2. Its lifetime is bound by the message loop of its origin thread
> 
> The purpose of this is to preserve the necessary threading discipline
> required by both the chrome.hid API implementation and the
> permission_broker DBus client while ensuring that the HidService is
> created and destroyed on the same thread.
> 
> BUG=401234
> 
> Committed: https://chromium.googlesource.com/chromium/src/+/13aca592b24cdeb9b558716db71c48961e48066f

TBR=reillyg@chromium.org,rpaquay@chromium.org,rockot@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=401234

[eroman, 2014-08-28 00:15:20]

Created Revert of Fix HidService lifetime issues.

[awong, 2014-08-28 00:21:09]

The CQ bit was unchecked by ajwong@chromium.org