The pipeline id stuff is currently unused. If someone needs it, they can add
an additional trait bound on their css error reporter to get the pipeline id.
Add 5 different task source channels
This is **not** complete. I really need feedback right away since I felt that the direction I'm heading is very wrong.
Partial #7959.
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Also change when pipelines become active.
This makes the constellation activate a pipeline as the current frame
when it is ready to do initial reflow, rather than when it is ready
to paint.
This fixes a number of intermittent failures that could previously occur
if an iframe was not visible - which would mean it was never moved from
a pending frame in the constellation to an active frame.
(It happens that webrender exposes these intermittents as permanent failures).
Opaque DOMString
This patch makes DOMString an opaque wrapper round String (currently it's a transparent wrapper).
The changes are:
* Replacing DOMString(foo) by DOMString::from(foo).
* Replacing foo.0 by String::from(foo).
* Adding functions clear, push_str and extend for in-place mutation of DOMStrings.
* Replacing DOMString by String in other threads (devtools, storage and filereader).
* Making DOMString implement !Send.
* Removing the pub attribute from the contents of DOMString.
This enables experimenting with other string representations in the DOM.
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Functions returning `Root<T>` are prefixed by "root_" and the ones returning
`*const T` by "native_".
Functions taking `*mut JSObject` are now suffixed by "_from_object" and the ones
taking `&T` by "_from_reflector".
Stylesheets for `HTMLLinkElement`s are now loaded by the resource task, triggered by the element in question. Stylesheets are owned by the elements they're associated with, which can be `HTMLStyleElement`, `HTMLLinkElement`, and `HTMLMetaElement` (for `<meta name="viewport">).
Additionally, the quirks mode stylesheet (just as the user and user agent stylesheets a couple of commits ago), is implemented as a lazy static, loaded once per process and shared between all documents.
This all has various nice consequences:
- Stylesheet loading becomes a non-blocking operation.
- Stylesheets are removed when the element they're associated with is removed from the document.
- It'll be possible to implement the CSSOM APIs that require direct access to the stylesheets (i.e., ~ all of them).
- Various subtle correctness issues are fixed.
One piece of interesting follow-up work would be to move parsing of external stylesheets to the resource task, too. Right now, it happens in the link element once loading is complete, so blocks the script task. Moving it to the resource task would probably be fairly straight-forward as it doesn't require access to any external state.
This should make it somewhat easier to experiment with alternative
representations in the future. To reduce churn, this commit leaves the String
field public, though.
Also, this will allow us to use the default String type to represent the IDL
USVString type, which explicitly forbids unpaired surrogates, ans as such is
a better match to the Rust String type.
