This is incomplete in several ways:
* It assumes that there's only one constellation (i.e. top level browsing context), ever.
* The session support is very basic indeed (no capabilities)
* Passing channels over channels may not sit well with IPC
* The error handling is mostly missing
<!-- Reviewable:start -->
[<img src="https://reviewable.io/review_button.png" height=40 alt="Review on Reviewable"/>](https://reviewable.io/reviews/servo/servo/5610)
<!-- Reviewable:end -->
This implements a framework for opting in to receiving network events asynchronously. It also converts XMLHttpRequest to use them, and paves the way for better support for synchronous XHR using on-demand, targeted event loops instead of spinning the global event loop. This gives us complete feature parity with the existing XHR implementation, using fewer threads than before in the async case.
<!-- Reviewable:start -->
[<img src="https://reviewable.io/review_button.png" height=40 alt="Review on Reviewable"/>](https://reviewable.io/reviews/servo/servo/5156)
<!-- Reviewable:end -->
This is incomplete in several ways:
* It assumes that there's only one constellation (i.e. top level browsing context), ever.
* The session support is very basic indeed (no capabilities)
* Passing channels over channels may not sit well with IPC
* The error handling is mostly missing
stacking contexts properly.
The code that existed before correctly translated the clips of child
elements, but not those of immediate display items belonging to the flow
itself.
Makes Leaflet.js maps usable.
Supported for Linux & Windows platforms.
If it fails to generate the desktop notification, it simply gives a soft warning on the terminal.
This PR is solving Issue #5582.
<!-- Reviewable:start -->
[<img src="https://reviewable.io/review_button.png" height=40 alt="Review on Reviewable"/>](https://reviewable.io/reviews/servo/servo/5664)
<!-- Reviewable:end -->
Before this change, Servo used one code path that computed the position
of flows with `position: static` or `position: relative` and another
separate code path that computed the position of flows with `position:
absolute` or `position: fixed`. The latter code attempted to duplicate
the former code to determine the static position of hypothetical boxes,
but this was both fragile and incorrect in the case of hypothetical
boxes nested inside floats. In fact, it's impossible to determine the
static position of an absolute flow relative to its containing block at
inline-size assignment time, because that static position could depend
on a float that cannot be placed until block-size assignment!
This patch changes block layout to use the same code path for static
positioning of regular flows and static positioning of absolute flows
where applicable. This both simplifies the code and improves its
efficiency, since it allows the `hypothetical_position` field and
`static_block_offsets` data structure to be removed. Moreover, it
improves correctness in the above case (which the new reftest checks).
This allows the sidebar in Facebook Timeline to be positioned properly.
r? @glennw
<!-- Reviewable:start -->
[<img src="https://reviewable.io/review_button.png" height=40 alt="Review on Reviewable"/>](https://reviewable.io/reviews/servo/servo/5691)
<!-- Reviewable:end -->
Extracted out of #5649
* add more hyperlinks to associated specification for structs/methods
* follow redirects and update links
* replace broken links
* removal of WHATWG multipage page name since the page name is not
guaranteed to be stable
<!-- Reviewable:start -->
[<img src="https://reviewable.io/review_button.png" height=40 alt="Review on Reviewable"/>](https://reviewable.io/reviews/servo/servo/5693)
<!-- Reviewable:end -->
Extracted out of #5649
* add more hyperlinks to associated specification for structs/methods
* follow redirects and update links
* replace broken links
* removal of WHATWG multipage page name since the page name is not
guaranteed to be stable
