Fix insertion location of <template> for declarative shadow roots

[shannonbooth]

Recomputing the adjusted insertion location after <template> was pushed
onto the stack of open elements caused it to be inserted into itself for
two templates in a row. Fix by reusing the location computed before
<template> is created.

NB: though this area was changed around recently in #12624, this issue existed before that.

• At least two implementers are interested (and none opposed):
  • All browsers implement
• Tests are written and can be reviewed and commented upon at:
  • https://github.com/web-platform-tests/wpt/blob/master/shadow-dom/declarative/declarative-shadow-dom-basic.html
  • https://github.com/web-platform-tests/wpt/blob/master/shadow-dom/declarative/declarative-shadow-dom-attachment.html
• Implementation bugs are filed:
  • Chromium: N/A
  • Gecko: N/A
  • WebKit: N/A
• Corresponding HTML AAM & ARIA in HTML issues & PRs: N/A
• MDN issue is filed: N/A
• The top of this comment includes a clear commit message to use.

(See WHATWG Working Mode: Changes for more details.)

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/parsing.html ( diff )

[noamr]

Thanks! Any reason this is marked as a draft?

[shannonbooth]

Thanks! Any reason this is marked as a draft?

Due to: #12666 (comment), I've pushed a commit with what I mean but that, just double checking it now. I think I will need to fill out the template and that type of thing, though I think this is the intent of the spec

[shannonbooth]

ok done!