Revert of Add UMA to track app launcher discoverability.

Revert of Add UMA to track app launcher discoverability. (https://codereview.chromium.org/143683004/)

Reason for revert:
Doesn't compile Google Chrome-branded builds:

src\chrome\browser\ui\views\app_list\win\app_list_service_win.cc(459) : error C2660: 'AppListServiceImpl::EnableAppList' : function does not take 1 arguments

Original issue's description:
> Add UMA to track app launcher discoverability.
> 
> We want to track effectiveness of the app launcher install education
> pages in enabling users to find, and start using, the app launcher when
> it is auto-enabled upon installing the first v2 packaged app. The
> launcher is not auto-shown for the "first" install, to encourage users
> to learn where it is.
> 
> This CL marks "how" the app launcher is enabled (e.g. command line flag,
> webstore, etc.), and when the enable occurs. Then, when the user shows
> the app list, the enable method and time taken to show it is recorded.
> 
> We also need to record users that "never" show the app list, or who see
> the app list show automatically upon installing a _second_ app. One hour
> is chosen as a timeout: if no value is recorded after one hour, a value
> is recorded in the "last" bucket for the time taken.
> 
> BUG=314235
> TBR=xiyuan@chromium.org
> 
> Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=250348

TBR=benwells@chromium.org,xiyuan@chromium.org,tapted@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=314235
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=250467

[grt (UTC plus 2), 2014-02-11 19:15:40]

Created Revert of Add UMA to track app launcher discoverability.

[commit-bot: I haz the power, 2014-02-11 19:17:20]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/grt@chromium.org/134303006/1

[commit-bot: I haz the power, 2014-02-11 19:19:51]

Change committed as 250467