Build WebRtcMediaEngine2 outside of Chromium.
Build WebRtcMediaEngine2 outside of Chromium.

Removes #ifdef WEBRTC_CHROMIUM_BUILD from
talk/media/webrtc/webrtcmediaengine.cc. WebRtcVideoEngine2 is built on
all platforms so there's no longer any need to guard this code under
ifdefs.

BUG=1788
R=sprang@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/42719004

Cr-Original-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#8679}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: e77c9c8df54d6a14a27e7c5e16bf55fb121426ef

sippet/talk,sippet/talk,sippet/talk,sippet/talk,sippet/talk