Reland of Add a webrtc{en,de}coderfactory implementation for VideoToolbox (patchset #1 id:1 of https://codereview.webrtc.org/2483273002/ )

Reason for revert:
Fix gyp build

Original issue's description:
> Revert of Add a webrtc{en,de}coderfactory implementation for VideoToolbox (patchset #2 id:20001 of https://codereview.webrtc.org/2463313002/ )
>
> Reason for revert:
> Broke dependent project because the .gn changes weren't accompanied by corresponding .gyp changes.
>
> Original issue's description:
> > Add a webrtc{en,de}coderfactory implementation for VideoToolbox
> >
> > This CL removes the coupling of the VideoToolbox h264 implementation
> > to the generic h264 code. The files have been moved into sdb/obj/Framework
> > and all dependency on them has been removed from the rest of WebRTC.
> > We now add it as an external encoder via a factory supplied to the
> > CreatePeerConnectionFactory call. This also brings the iOS implementation
> > closer to what we do on Android for MediaCodec.
> >
> > BUG=webrtc:6619
> >
> > Committed: https://crrev.com/6a5047dad31f14f53dd9f8bc1ecde19e1dede2e4
> > Cr-Commit-Position: refs/heads/master@{#14953}
>
> TBR=magjed@webrtc.org,stefan@webrtc.org,kthelgason@webrtc.org
> BUG=webrtc:6619
>
> Committed: https://crrev.com/d69ad84420d9c0e1c11450c352f6c92e7c9583f1
> Cr-Commit-Position: refs/heads/master@{#14985}

R=magjed@webrtc.org
TBR=kwiberg@webrtc.org, magjed@webrtc.org, stefan@webrtc.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=webrtc:6619

Review URL: https://codereview.webrtc.org/2487723004 .

Cr-Original-Commit-Position: refs/heads/master@{#14992}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: cbe743528848dc71e6bc15185002a634b78661c6
diff --git a/sdk/DEPS b/sdk/DEPS
index d6e53d5..137f67a 100644
--- a/sdk/DEPS
+++ b/sdk/DEPS
@@ -2,6 +2,8 @@
   "+WebRTC",
   "+webrtc/api",
   "+webrtc/common_video/include",
+  "+webrtc/common_video/h264",
   "+webrtc/media",
+  "+webrtc/modules/video_coding",
   "+webrtc/system_wrappers",
 ]