Rename Launcher to Shelf.

- move launcher* from launcher to shelf.
- rename to launcher.* to shelf.* and launcher_unittest.cc to
shelf_unittest.cc

- rename LauncherTestAPI to ShelfTestAPI.
- rename to launcher_test_api.* to shelf_test_api.*

BUG=248353
TEST=None, no functional changes
R=jamescook@chromium.org,harrym@chromium.org
TBR=sky

Review URL: https://codereview.chromium.org/115113006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@241794 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 241794