Move clients of BrowserContextKeyedService to using KeyedService (#3)

This CL moves the following clients of BCKS to using the KeyedService
component:

- //apps
- //chrome/browser/apps
- //chrome/browser/chromeos
- //chrome/browser/managed_mode

BUG=351704
TBR=yoz,jochen

Review URL: https://codereview.chromium.org/197733002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@256756 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 256756