Changing MultiprocessTestClient to use base ChildProcessLauncher.

Now that ChildProcessLauncher has been moved to base, changed the
MultiprocessTestClient to use it instead of duplicating the
functionality.

Bug: 702316
Change-Id: I3828f7cf16d815b45c7aca9925ef4b69866e66f4
Reviewed-on: https://chromium-review.googlesource.com/562519
Commit-Queue: Jay Civelli <jcivelli@chromium.org>
Reviewed-by: Tommy Nyquist <nyquist@chromium.org>
Cr-Commit-Position: refs/heads/master@{#486691}
2 files changed