Fix Gn untracked headers in webrtc/media BUG=webrtc:7645 Review-Url: https://codereview.webrtc.org/3013063002 Review-Url: https://codereview.webrtc.org/3018473002 Cr-Original-Commit-Position: refs/heads/master@{#19844} Cr-Original-Original-Commit-Position: refs/heads/master@{#19824} Cr-Mirrored-From: https://webrtc.googlesource.com/src Cr-Mirrored-Commit: 6674846b4adc999f69bfdb12080749d4e4ab729d