Removed experimental app list flags. Experimental is now the only way.

Removed --enable/disable-experimental-app-list and
--enable-centered-app-list flags. Now always behaves as if experimental
(which was the default). This effectively removes the old
lower-left-corner tall app launcher (although all the code is still
there; it will be removed in a follow-up CL).

This cleans up the tests that set those switches, and removes tests that
test the old app launcher behaviour.

BUG=531059

Review-Url: https://codereview.chromium.org/2342773002
Cr-Commit-Position: refs/heads/master@{#419405}
10 files changed