image fragments.
This also changes the way the placeholder is handled in the image cache
task to decode it up front instead of each time an image fails to load,
both because it was more convenient to implement that way and because
it saves CPU cycles to do so.
This matches the behavior of Gecko and WebKit. It improves the look of
our cached copy of Wikipedia.
* Simpler image cache API for clients to use.
* Significantly fewer threads.
* One thread for image cache task (multiplexes commands, decoder threads and async resource requests).
* 4 threads for decoder worker tasks.
* Removed ReflowEvent hacks in script and layout tasks.
* Image elements pass a Trusted<T> to image cache, which is used to dirty nodes via script task. Previous use of Untrusted addresses was unsafe.
* Image requests such as background-image on layout / paint threads trigger repaint only rather than full reflow.
* Add reflow batching for when multiple images load quickly.
* Reduces the number of paints loading wikipedia from ~95 to ~35.
* Reasonably simple to add proper prefetch support in a follow up PR.
* Async loaded images always construct Image fragments now, instead of generic.
* Image fragments support the image not being present.
* Simpler implementation of synchronous image loading for reftests.
* Removed image holder.
* image.onload support.
* image NaturalWidth and NaturalHeight support.
* Updated WPT expectations.
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
This exposes some other canvas tests which were marked as PASS before. Two strokeRect related tests are fixed by #5612, and lineCap/lineJoin will have an implementation soon.
For the majority of these cases, `as_slice` can be removed due to
`Deref`. In particular, `Deref` for:
* `String` -> `str`
* `Atom` -> `str`
The latter of those two requires, a bump of the locked `string-cache`
library
http://www.w3.org/html/wg/drafts/2dcontext/html5_canvas_CR/ says
"Except where otherwise specified, for the 2D context interface,
any method call with a numeric argument whose value is infinite or a
NaN value must be ignored."
We might define the annotation to generate this behavior in glue code.
However, at now, I use this workaround way.
