Gecko has both:
https://github.com/mozilla/gecko-dev/blob/9c9e0b6c604a8bbdca122f3557c600f138438550/dom/webidl/RTCPeerConnection.webidl#L39

Is it acceptable to simply transform `maxRetransmitTime` to `maxPacketLifeTime`, or do these mean fundamentally different things? I ask, because I write a library that intends to paper over this difference between what is currently implemented in Chrome, versus Firefox, versus Safari, versus the spec, etc. webrtc/adapter may also want to implement this.

Answering my own question: based on https://www.w3.org/Bugs/Public/show_bug.cgi?id=25155 these should be the same.

Can you fix this? It results in silent creation of reliable data channels which is bad.

hbos@: Can you take a look?

Chrome status link, to link to in a deprecation notice: https://www.chromestatus.com/feature/5198350873788416

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/035d038b828db503c8a4c597d351f8b5f04b24f8

commit 035d038b828db503c8a4c597d351f8b5f04b24f8
Author: Taylor Brandstetter <deadbeef@chromium.org>
Date: Tue Jun 19 21:55:28 2018

Add support for RTCDataChannelInit.maxPacketLifeTime.

This is just the standardized name for "maxRetransmitTime", which
we've already supported for a while.

Also adding deprecation notice saying that maxRetransmitTime is being
replaced by maxPacketLifeTime and will be removed in M70.

Bug:  chromium:696681 
Change-Id: I14dc14ebc103bb3f6a233fd753d9ffbd1dd734d6
Reviewed-on: https://chromium-review.googlesource.com/1101473
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Commit-Queue: Taylor Brandstetter <deadbeef@chromium.org>
Cr-Commit-Position: refs/heads/master@{#568610}
[modify] https://crrev.com/035d038b828db503c8a4c597d351f8b5f04b24f8/third_party/WebKit/LayoutTests/external/wpt/webrtc/RTCPeerConnection-createDataChannel-expected.txt
[modify] https://crrev.com/035d038b828db503c8a4c597d351f8b5f04b24f8/third_party/WebKit/LayoutTests/fast/peerconnection/RTCPeerConnection-datachannel-expected.txt
[modify] https://crrev.com/035d038b828db503c8a4c597d351f8b5f04b24f8/third_party/blink/public/platform/web_feature.mojom
[modify] https://crrev.com/035d038b828db503c8a4c597d351f8b5f04b24f8/third_party/blink/renderer/core/frame/deprecation.cc
[modify] https://crrev.com/035d038b828db503c8a4c597d351f8b5f04b24f8/third_party/blink/renderer/modules/peerconnection/rtc_data_channel_init.idl
[modify] https://crrev.com/035d038b828db503c8a4c597d351f8b5f04b24f8/third_party/blink/renderer/modules/peerconnection/rtc_peer_connection.cc
[modify] https://crrev.com/035d038b828db503c8a4c597d351f8b5f04b24f8/tools/metrics/histograms/enums.xml

Created a separate bug for removing maxRetransmitTime: https://bugs.chromium.org/p/chromium/issues/detail?id=854385