Without this, the rtc_media_unittests target was only an indirect dependency, and compiled without HAVE_WEBRTC_VIDEO. And some testcases, in particular, all tests defined by webrtcvideocapturer_unittest.cc, are excluded from rtc_media_unittests. BUG= Review-Url: https://codereview.webrtc.org/2250433008 Cr-Commit-Position: refs/heads/master@{#13859}