Update WebGL tests
There is in fact nothing to update because we use upstream's snapshots from `conformance-suites/`, we should consider syncing with `sdk/tests/` instead.
<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/21507)
<!-- Reviewable:end -->
Update README.md
add `gstreamer` to `dnf install`
<!-- Please describe your changes on the following line: -->
---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data: -->
- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes not fix#21446, but help to compile.
<!-- Either: -->
- [x] There are tests for these changes OR
- [x] These changes do not require tests because it only change README.md
<!-- Also, please make sure that "Allow edits from maintainers" checkbox is checked, so that we can help you if you get stuck somewhere along the way.-->
<!-- Pull requests that do not address these steps are welcome, but they will require additional verification as part of the review process. -->
<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/21499)
<!-- Reviewable:end -->
Replace Servo DL items with WR ones
The Servo internal display list items are already pretty much
equivalent to the WebRender ones. Except that Servo items contain
base information and associated glyphs and gradient stops which are
stored implicitly in WebRender. Remove the display items for
rectangles, text, images, border, gradients and box shadow and
replace them with their WebRender counter parts.
Some more internal items like line, text shadow and iframe can definitively be replaced with WebRender equivalents but I think the PR is already quite huge. If WebRender would expose a quite minimal API which allowed servo to directly push items onto the display list most of webrender_helpers boilerplate code could go away. As WebRender performs normalization of gradients this would need to be called by servo explicitly in this case.
It should be noted that gradient borders don't actually work neither with the old version nor with this PR as the measurements are all set to zero.
Part of #19676
<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/21348)
<!-- Reviewable:end -->
appveyor: Append to LIB variable instead of overwriting it.
- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes fix#21489
- [x] There are tests for these changes
<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/21490)
<!-- Reviewable:end -->
Remove outdated comment in stylist.rs
<!-- Please describe your changes on the following line: -->
This comment on `cascade_style_and_visited` is unclear because it refers to `is_link`, which is not a parameter of that function. It used to refer to a flag in `CascadeFlags` back when there was a `cascade_flags: CascadeFlags` parameter; that parameter was removed in commit cd04664. I don't believe it accurately reflects how the code works anymore, and is best just removed.
---
<!-- 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` does not report any errors
- [ ] These changes fix #__ (github issue number if applicable).
<!-- Either: -->
- [ ] There are tests for these changes OR
- [X] These changes do not require tests because they only touch comments
<!-- Also, please make sure that "Allow edits from maintainers" checkbox is checked, so that we can help you if you get stuck somewhere along the way.-->
<!-- Pull requests that do not address these steps are welcome, but they will require additional verification as part of the review process. -->
<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/21487)
<!-- Reviewable:end -->
Fix zoom keybindings
- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes fix#21457 (github issue number if applicable).
<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/21477)
<!-- Reviewable:end -->
List additional keyboard shortcuts
<!-- Please describe your changes on the following line: -->
---
<!-- 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` does not report any errors
- [ ] These changes fix #__ (github issue number if applicable).
<!-- Either: -->
- [ ] There are tests for these changes OR
- [ ] These changes do not require tests because _____
<!-- Also, please make sure that "Allow edits from maintainers" checkbox is checked, so that we can help you if you get stuck somewhere along the way.-->
<!-- Pull requests that do not address these steps are welcome, but they will require additional verification as part of the review process. -->
<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/21460)
<!-- Reviewable:end -->
Add `autoconf` as required dependency for macOS
Update README
---
- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes fix#21471
- [x] These changes do not require tests
<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/21472)
<!-- Reviewable:end -->
Fix Android back button behavior
Pressing the back button should call mServoView.goBack if possible.
<!-- Please describe your changes on the following line: -->
---
<!-- 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` does not report any errors
- [X] These changes fix#21401 (github issue number if applicable).
<!-- Either: -->
- [ ] There are tests for these changes OR
- [ ] These changes do not require tests because _____
<!-- Also, please make sure that "Allow edits from maintainers" checkbox is checked, so that we can help you if you get stuck somewhere along the way.-->
<!-- Pull requests that do not address these steps are welcome, but they will require additional verification as part of the review process. -->
<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/21439)
<!-- Reviewable:end -->
Upgrade to SM 60
<!-- Please describe your changes on the following line: -->
This is the mozjs_sys smup PR. Depends on https://github.com/servo/mozjs/pull/138 and https://github.com/servo/rust-mozjs/pull/430.
---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data: -->
- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes fix#20585
<!-- Either: -->
- [X] These changes do not require tests because the existing tests will ensure SM is still working
<!-- Also, please make sure that "Allow edits from maintainers" checkbox is checked, so that we can help you if you get stuck somewhere along the way.-->
<!-- Pull requests that do not address these steps are welcome, but they will require additional verification as part of the review process. -->
<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/21029)
<!-- Reviewable:end -->
Revert "build(mach): locate vs via vswhere on win32"
This reverts commit c20efd5e9a. It doesn't work on a new windows builder that only has the build tools installed, where no products are reported present; I would rather put us back in a state that works rather than try to deal with that issue.
<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/21464)
<!-- Reviewable:end -->
Remove warnings about WPT syncing process.
The process is well understood now and they're just annoying to remove every time.
<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/21434)
<!-- Reviewable:end -->
Network: Preserve HEAD on 303 redirect
fixed#21449. This is an update for spec.
This PR just update one step for redirect fetch according to spec. No tests result change, since the whole process is still in development(So many todo).
<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/21454)
<!-- Reviewable:end -->
README: clarify Mac keyboard shortcuts
<!-- Please describe your changes on the following line: -->
Add clarifications to the README's section on keyboard shortcuts for Mac users.
Relatedly, I couldn't get the zoom-related shortcuts to work at all on Mac; I tried each of `Ctrl`, `Opt`, and `Cmd` with `-` and `=` on a couple different webpages. I can file a separate issue for that if it's warranted, or amend this PR to add a note to the README for this as well.
---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data: -->
- [X] `./mach build -d` does not report any errors
- [ ] `./mach test-tidy` does not report any errors
- [ ] These changes fix #__ (github issue number if applicable).
<!-- Either: -->
- [ ] There are tests for these changes OR
- [X] These changes do not require tests because they only touch the README
<!-- Also, please make sure that "Allow edits from maintainers" checkbox is checked, so that we can help you if you get stuck somewhere along the way.-->
<!-- Pull requests that do not address these steps are welcome, but they will require additional verification as part of the review process. -->
<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/21447)
<!-- Reviewable:end -->
