Process all pending lazy loading intersection observations

[shannonbooth]

Otherwise images outside the viewport can prevent loading of images inside the viewport, depending on DOM order.

Fixes: #10019

• At least two implementers are interested (and none opposed):
  • Chromium/Safari/Firefox all pass the WPT
• Tests are written and can be reviewed and commented upon at:
  • Test lazy loading intersection observations outside viewport web-platform-tests/wpt#59333
• Implementation bugs are filed:
  • Chromium: Already implements
  • Gecko: Already implements
  • WebKit: Already implements
• 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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/media.html ( diff )
/urls-and-fetching.html ( diff )