Reason for revert:
It breaks a downstream project.
Original issue's description:
> Decoupling rtc_base from Obj-C code
>
> The goal of this CL is to separate Obj-C/Obj-C++ code from targets which have
> also C++ code (see https://bugs.chromium.org/p/webrtc/issues/detail?id=7743
> for more information).
>
> To achieve this we have created 2 targets (rtc_base_objc and rtc_base_generic)
> and rtc_base will act as a proxy between these targets (this way we can avoid a
> circular dependency between rtc_base_generic and rtc_base_objc).
>
> BUG=webrtc:7743
>
> Review-Url: https://codereview.webrtc.org/3001623003
> Cr-Commit-Position: refs/heads/master@{#19661}
> Committed: a0a5b98937
TBR=kjellander@webrtc.org,kwiberg@webrtc.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=webrtc:7743
Review-Url: https://codereview.webrtc.org/3008103002
Cr-Commit-Position: refs/heads/master@{#19664}
Name: WebRTC URL: http://www.webrtc.org Version: 90 License: BSD License File: LICENSE Description: WebRTC provides real time voice and video processing functionality to enable the implementation of PeerConnection/MediaStream. Third party code used in this project is described in the file LICENSE_THIRD_PARTY.