Fix Chrome unit tests when using the audio service.

WebContentsImpl accesses ServiceManagerConnection when we're
toggling muting using the audio service. This is always set
in production, but in tests we need to make sure that it is
initialized.

Tbr: markusheintz
Bug: 843103
Change-Id: Ief7819edbeed6616e9e7defb5860b422f6862f9b
Reviewed-on: https://chromium-review.googlesource.com/1062038
Commit-Queue: Max Morin <maxmorin@chromium.org>
Reviewed-by: Becca Hughes <beccahughes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#559860}
2 files changed