Adding support for launching firefox from webrtc.DEPS.

This is required for the firefox interop test being added in
https://codereview.chromium.org/111383003/.

This is only intended to work for Linux for now. We will need some light
redesign to get this to work on Windows as well.

R=kjellander@chromium.org

Review URL: https://codereview.chromium.org/114293002

git-svn-id: http://src.chromium.org/svn/trunk/deps/third_party/webrtc/webrtc.DEPS@240895 4ff67af0-8c30-449e-8e8b-ad334ec8d88c
3 files changed