Advance to stage 4

[mathiasbynens]

Criteria taken from the TC39 process document minus those from previous stages:

• Test262 acceptance tests have been written for mainline usage scenarios, and merged

PR by @spectranaut: tc39/test262#1246

• Two compatible implementations which pass the acceptance tests

https://github.com/tc39/proposal-string-left-right-trim#implementations

• Significant in-the-field experience with shipping implementations, such as that provided by two independent VMs

https://github.com/tc39/proposal-string-left-right-trim#implementations

• A pull request has been sent to https://github.com/tc39/ecma262 with the integrated spec text

PR by @evilpie: tc39/ecma262#1275

• The ECMAScript editor has signed off on the pull request

[ljharb]

I believe you can check the last box, but you’ll want to add a final box “committee consensus” :-)

[ljharb]

This can be closed; the proposal is stage 4 and in ES2019.