Go through style::hash for the TransitionProperty set

[bholley]

In #18604, emilio switched us from hash::HashSet to std::collections::HashSet for the TransitionProperty set. In turn, this means that Manishearth's change in #18712 didn't catch this use of DefaultHasher. This means that we still have usage of RandomState in stylo, which means that we'll still have crashes on the systems where RandomState breaks.

Mentions moved to a comment to avoid email spam down the road.

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This change is 

[highfive]

Heads up! This PR modifies the following files:

• @canaltinova: components/style/gecko/wrapper.rs
• @emilio: components/style/gecko/wrapper.rs

[highfive]

Warning

• These commits modify style code, but no tests are modified. Please consider adding a test!

[bholley]

Also note that I fixed this in the beta uplift in [1], which is actually how I noticed it, since #18604 is not on beta.

[1] https://bugzilla.mozilla.org/show_bug.cgi?id=1385971

[bholley]

CC various other style/ people to be aware that we should avoid any usage of DefaultHasher and that all usage should go through style::hash @SimonSapin @nox @upsuper @hiikezoe @birtles @heycam @Manishearth @emilio

[upsuper]

@bors-servo r+

You should probably remove the @ to manish and emilio as well.

[bors-servo]

📌 Commit db6bfe9 has been approved by upsuper

[bholley]

@bors-servo p=1

[upsuper]

We still have several usage of std::collections for build script and custom derive code. I guess those are fine, since they are not built into the final code.

[emilio]

@bors-servo r-

• The fix for https://bugzilla.mozilla.org/show_bug.cgi?id=1406111 will make this no longer a HashSet.

[emilio]

That fix is #18763

[hiikezoe]

Just to clarify, both this and #18763 don't need to be uplifted to 57, right?

[hiikezoe]

Oops, I missed Bobby's comment, this has been already uplifted to 57.

[bors-servo]

☔ The latest upstream changes (presumably #18763) made this pull request unmergeable. Please resolve the merge conflicts.

[emilio]

That hash is no more.