Unprefixing was  issue 649331  and  issue 658423 . That Edge has MediaStream but not webkitMediaStream makes the odds for that working out pretty good.

Safari 11 has just shipped WebRTC without these prefixed interfaces, suggesting that it's probably low risk to remove these.

kereliuk@, this won't be on any OKRs explicitly, but if you want to try some web platform cleanup work, this would be a good candidate, that also is relevant to your other work in Q4.

webkitGetUserMedia is issue 692736, so changing title.

Filed https://github.com/webrtc/adapter/issues/712 about a problem with adapter.js that complicates removal.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/a4e071f707e430047f7fc218bd71db44c2216905

commit a4e071f707e430047f7fc218bd71db44c2216905
Author: Philip Jägenstedt <foolip@chromium.org>
Date: Mon Jan 29 08:21:44 2018

Remove internal use of webkitMediaStream and webkitRTCPeerConnection

This is a no-op change that makes it easier to later remove them.

The copyright license is required to pass presubmit.

Bug: 690582
Change-Id: I8f4074102dff3ef87b35d239f06ce2c93246d88d
Reviewed-on: https://chromium-review.googlesource.com/693861
Reviewed-by: Tommi <tommi@chromium.org>
Commit-Queue: Philip Jägenstedt <foolip@chromium.org>
Cr-Commit-Position: refs/heads/master@{#532348}
[modify] https://crrev.com/a4e071f707e430047f7fc218bd71db44c2216905/chrome/test/data/webrtc/adapter.js
[modify] https://crrev.com/a4e071f707e430047f7fc218bd71db44c2216905/chrome/test/data/webrtc/webrtc-simulcast.html

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/cfb13462393288781b461b2d911edfa75311ad06

commit cfb13462393288781b461b2d911edfa75311ad06
Author: Philipp Hancke <philipp.hancke@googlemail.com>
Date: Mon Jan 29 15:51:06 2018

remove unused code from internal webrtc-adapter.js

Removed all code in adapter.js that was not for Chrome, for
very outdated versions of Chrome or not used anywhere.

This file is a very old version of the project now residing on
    https://github.com/webrtc/adapter

Bug: 690582
Change-Id: I21fa60fd86962dadbcec1650201fc13e932b736e
Reviewed-on: https://chromium-review.googlesource.com/889755
Reviewed-by: Harald Alvestrand <hta@chromium.org>
Reviewed-by: Tommi <tommi@chromium.org>
Commit-Queue: Harald Alvestrand <hta@chromium.org>
Cr-Commit-Position: refs/heads/master@{#532441}
[modify] https://crrev.com/cfb13462393288781b461b2d911edfa75311ad06/chrome/test/data/webrtc/adapter.js

adapter.js no longer relies on webkitRTCPeerConnection as of patch release 6.1.1.

It still does rely on webkitGetUserMedia which probably needs a breaking major release.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/7cdabea17270748593b5c693eb46fab03a674c2f

commit 7cdabea17270748593b5c693eb46fab03a674c2f
Author: Philipp Hancke <philipp.hancke@googlemail.com>
Date: Thu Feb 01 10:56:37 2018

webrtc: remove legacy adapter.js from tests

removes the last test dependencies on adapter.js and the file itself.

Bug: 690582
Change-Id: I662be702b4ede801b9175066490e662a1ea41776
Reviewed-on: https://chromium-review.googlesource.com/895302
Commit-Queue: Harald Alvestrand <hta@chromium.org>
Reviewed-by: Harald Alvestrand <hta@chromium.org>
Cr-Commit-Position: refs/heads/master@{#533628}
[delete] https://crrev.com/7faa4aa64e3aea91be3e95bb55506e970742ecfd/chrome/test/data/webrtc/adapter.js
[modify] https://crrev.com/7cdabea17270748593b5c693eb46fab03a674c2f/chrome/test/data/webrtc/getusermedia.js
[modify] https://crrev.com/7cdabea17270748593b5c693eb46fab03a674c2f/chrome/test/data/webrtc/peerconnection.js
[modify] https://crrev.com/7cdabea17270748593b5c693eb46fab03a674c2f/chrome/test/data/webrtc/peerconnection_rtp.js
[modify] https://crrev.com/7cdabea17270748593b5c693eb46fab03a674c2f/chrome/test/data/webrtc/webrtc_audio_quality_test.html
[modify] https://crrev.com/7cdabea17270748593b5c693eb46fab03a674c2f/chrome/test/data/webrtc/webrtc_jsep01_test.html
[modify] https://crrev.com/7cdabea17270748593b5c693eb46fab03a674c2f/chrome/test/data/webrtc/webrtc_video_quality_test.html

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/b6ee724f019226b783cd34cf8afba73d667b9e50

commit b6ee724f019226b783cd34cf8afba73d667b9e50
Author: Harald Alvestrand <hta@chromium.org>
Date: Mon Sep 03 08:30:40 2018

Count usage of webkit-prefixed objects

This counts usage of webkitMediaStream constructor
and of webkitRTCPeerConnection constructor.

Counting is a preliminary to removing them.

Bug: chromium:690582
Change-Id: Iadb41a8d0039c3a1218f87032971598f21ce4e16
Reviewed-on: https://chromium-review.googlesource.com/1199107
Reviewed-by: Guido Urdaneta <guidou@chromium.org>
Reviewed-by: Philip Jägenstedt <foolip@chromium.org>
Commit-Queue: Harald Alvestrand <hta@chromium.org>
Cr-Commit-Position: refs/heads/master@{#588350}
[modify] https://crrev.com/b6ee724f019226b783cd34cf8afba73d667b9e50/third_party/blink/public/platform/web_feature.mojom
[modify] https://crrev.com/b6ee724f019226b783cd34cf8afba73d667b9e50/third_party/blink/renderer/modules/mediastream/window_media_stream.idl
[modify] https://crrev.com/b6ee724f019226b783cd34cf8afba73d667b9e50/tools/metrics/histograms/enums.xml