Cleanup after talk/media move.
Cleanup after talk/media move.

More work remains, but is less urgent.
webrtc/media/base/mediacommon.h could not be deleted since
the constants are used in multiple places.

BUG=webrtc:5420
TBR=pthatcher@webrtc.org

Review URL: https://codereview.webrtc.org/1688753002 .

Cr-Original-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#11551}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: e2812e74fb46514a31b20a1bd012d82f75ddfdaa

Alkalyne/webrtctrunk,Alkalyne/webrtctrunk,jchavanton/webrtc,Alkalyne/webrtctrunk,jchavanton/webrtc,Alkalyne/webrtctrunk,Alkalyne/webrtctrunk,Alkalyne/webrtctrunk,Alkalyne/webrtctrunk,jchavanton/webrtc,Alkalyne/webrtctrunk,jchavanton/webrtc,jchavanton/webrtc,jchavanton/webrtc,jchavanton/webrtc