Null image source check for src, srcset and picture parent
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This PR includes a test which checks for empty src only.
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Implement document load cancellation
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script: A couple mutation observer fixes.
I felt like doing Servo stuff while trying to catch Gecko intermittents :)
This fixes most of #21233. I haven't dug into the other test.
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Implement update source set & select image source
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Make fetch() API use same-origin credentials by default
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Allow supported window attributes to be replacable.
As seen in https://github.com/servo/servo/pull/21045 some Window attributes don't support JavaScript from being able to shadow and replace their values.
This PR adds all other attributes I could find that are supported by servo to be replaceable.
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textarea minLength/maxLength
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textarea minLength/maxLength
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Let the popstate and hashchange events not bubble
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fix#21063
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