Hold references to the pre-patched environment to prevent calling into later-applied polyfills.

[bicknellr]

Most of this PR is leading whitespace changes:
https://github.com/webcomponents/custom-elements/pull/102/files?w=1

[snuggs]

@bicknellr VERY slick! I <3 it.

[bicknellr]

For reference, this JSBin (forked from this one, produced by @robdodson, to force the polyfills) shows a symptom of the current polyfills' layering problems. In particular, the first element should be able to find the second during its connectedCallback because the element construction and insertion is atomic and all the connectedCallback reactions should happen afterwards. Currently, the polyfills call into each other incorrectly in such a way that each individual child node of the constructed result of the set to innerHTML is inserted in its own step, with any connectedCallback reactions being called before moving on to inserting the next child.

[snuggs]

@bicknellr this explains so much! Been through this project a bunch of times and have to understand sometimes things are just the way they are just because!

[bicknellr]

I didn't really include much description for the PR beyond the title; Rob recently ran across the issue being fixed here and showed me that link so I figured I'd add it here since for more context.

things are just the way they are just because!

If you find something that isn't explained well, let me know and I'd be happy to answer questions and/or add docs as needed.

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[dfreedm]

Remaking this PR in the polyfills monorepo!