chromeos: updates BrowserWithTestWindowTest for mash

makes it call to AshTestHelper to create MusClient. This also moves
creation slightly earlier as some tests may need MusClient earlier.

BUG=910241
TEST=covered by tests

Change-Id: I434716e8cbdf91a2af27330f53b7ddef331b6c82
Reviewed-on: https://chromium-review.googlesource.com/c/1377721
Reviewed-by: James Cook <jamescook@chromium.org>
Commit-Queue: Scott Violet <sky@chromium.org>
Cr-Commit-Position: refs/heads/master@{#616718}
1 file changed