Revert of Update build files to use webrtc_overrides in Chromium instead of overrides.

Revert of Update build files to use webrtc_overrides in Chromium instead of overrides. (patchset #2 id:20001 of https://codereview.webrtc.org/1354933002/ )

Reason for revert:
Breaks FYI bots.

ninja: error: '../../third_party/webrtc_overrides/webrtc/base/logging.cc', needed by 'obj/third_party/webrtc_overrides/webrtc/base/rtc_base.logging.o', missing and no known rule to make it

Original issue's description:
> Update build files to use webrtc_overrides in Chromium instead of overrides.
>
> This is a part of moving the overrides to Chromium. See bug comment #65 for all steps.
>
> BUG=chromium:468375
>
> Committed: https://crrev.com/baae0a8a6c873ddf812a5687b84638359b2e7e5b
> Cr-Commit-Position: refs/heads/master@{#9996}

TBR=kjellander@webrtc.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=chromium:468375
Committed: https://crrev.com/40bf49375426132834589263efd1efbb177ef7b2
Cr-Commit-Position: refs/heads/master@{#9998}

[Henrik Grunell WebRTC, 2015-09-21 10:29:18]

Created Revert of Update build files to use webrtc_overrides in Chromium instead
of overrides.

[commit-bot: I haz the power, 2015-09-21 10:29:21]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1352423002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1352423002/1

[commit-bot: I haz the power, 2015-09-21 10:29:28]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-09-21 10:29:37]

Patchset 1 (id:??) landed as
https://crrev.com/40bf49375426132834589263efd1efbb177ef7b2
Cr-Commit-Position: refs/heads/master@{#9998}

[kjellander_webrtc, 2015-09-21 10:35:53]

On 2015/09/21 10:29:37, commit-bot: I haz the power wrote:
> Patchset 1 (id:??) landed as
> https://crrev.com/40bf49375426132834589263efd1efbb177ef7b2
> Cr-Commit-Position: refs/heads/master@{#9998}

We spoke offline, but FTR: you need to land the Chromium CL so webrtc_overrides
exists in Chromium first. Then this should be able to land without breaking our
roll-bots.