Ensure that a navigation to the same URL is aborted. Fixes #10952.

[emilio]

Thank you for contributing to Servo! Please replace each [ ] by [X] when the step is complete, and replace __ with appropriate data:

• ./mach build -d does not report any errors
• ./mach test-tidy --faster does not report any errors
• These changes fix #10952 (github issue number if applicable).

Either:

• There are tests for these changes.

Pull requests that do not address these steps are welcome, but they will require additional verification as part of the review process.

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Rebase of #10954

r? @jdm for the rebase (r=me for the original changes)

@jdm: Should this test still live in wpt? I'm tempted to move it to mozilla/ until whatwg/html#1177 is resolved.

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This change is

[highfive]

Heads up! This PR modifies the following files:

• @KiChjang: components/script/script_thread.rs

[jdm]

I agree, we should keep it as a local test until we achieve consensus.

[jdm]

I'm tempted to fix this in the same manner as Gecko instead. Location::SetHash can check for an empty string and pass "#" instead, which will set the fragment to Some("") rather than None, which means the existing navigation short-circuit code will Just Work.

[jdm]

whatwg/html#1318 agrees with me.

[bors-servo]

☔ The latest upstream changes (presumably #11434) made this pull request unmergeable. Please resolve the merge conflicts.

[jdm]

Closed in favour of #11934.

[KiChjang]

#11934 is about a special case location hash string, whereas this is about preventing navigation to the same URL. Should this be reopened?

[emilio]

@KiChjang: I don't think so, this was a way to tackle the same underlying problem, but the spec resolution was to take the approach of #11934 :)