This should load the "src.js":
```
const s = document.createElement('script');
document.getElementsByTagName('body')[0].appendChild(s);
s.src = "src.js"
```
Notice that src is set AFTER the element is added to the DOM. This PR enables
the above, by
1 - skipping dynamically added scripts which don't have a src
2 - trying to load a script whenever `set_src` is called.
(2) is safe because the ScriptManager already prevents scripts from being
processed multiple times.
Additionally, not only can the src be set after the script is added to the DOM,
but onload and onerror can be set after the src:
```
s.src = "src.js"
s.onload = ...;
s.onerror = ...;
```
This PR also delays reading the onload/onerror callbacks until the script is
done loading.
This behavior is seen on reddit.
Previously, the IO loop was doing three things:
1 - Managing timeouts (either from scripts or for our own needs)
2 - Handling browser IO events (page/script/xhr)
3 - Handling CDP events (accept, read, write, timeout)
With the libcurl merge, 1 was moved to an in-process scheduler and 2 was moved
to libcurl's own event loop. That means the entire loop code, including
the dependency on tigerbeetle-io existed for handling a single TCP client.
Not only is that a lot of code, there was also friction between the two loops
(the libcurl one and our IO loop), which would result in latency - while one
loop is waiting for the events, any events on the other loop go un-processed.
This PR removes our IO loop. To accomplish this:
1 - The main accept loop is blocking. This is simpler and works perfectly well,
given we only allow 1 active connection.
2 - The client socket is passed to libcurl - yes, libcurl's loop can take
arbitrary FDs and poll them along with its own.
In addition to having one less dependency, the CDP code is quite a bit simpler,
especially around shutdowns and writes. This also removes _some_ of the latency
caused by the friction between page process and CDP processing. Specifically,
when CDP now blocks for input, http page events (script loading, xhr, ...) will
still be processed.
There's still friction. For one, the reverse isn't true: when the page is
waiting for events, CDP events aren't going to be processed. But the page.wait
already have some sensitivity to this (e.g. the page.request_intercepted flag).
Also, when CDP waits, while we will process network events, page timeouts are
still not processed. Because of both these remaining issues, we still need to
jump between the two loops - but being able to block on CDP (even for a short
time) WITHOUT stopping the page's network I/O, should reduce some latency.
chromedb doesn't support duplicate header names. Although servers _will_ send
this (e.g. Cache-Control: public\r\nCache-Control: max-age=60\r\n), Chrome
seems to join them with a "\n". So we do the same.
A note on curl_easy_nextheader, which this code ultimately uses to iterate
and collect the headers. The documentation says:
Applications must copy the data if they want it to survive subsequent API
calls or the life-time of the easy handle.
As-is, I'd understand this to mean that a given header name/value is only
valid until any API call, including another call to curl_easy_nextheader. So,
from this comment, we _should_ be duping the name/value. But we don't. Why?
Because, despite the note in the documentation, this doesn't appear to be how
it actually works, nor does it really make sense. If it's just a linked list,
there's no reason curl_easy_nextheader should invalidate previous results. I'm
guessing this is just a general lack of guarantee libcurl is willing to make re
lifetimes.
https://github.com/lightpanda-io/browser/issues/966
Minor improvement to correctness of TreeWalker.
Fun fact, this is the first time, that I've run into, where we have to default
null and undefined to different values.
Also, tweaked the WPT test runner. WPT test results use | as a field delimiter.
But a WPT test (and, I assume a message) can contain a |. So we had at least
a few tests that were being reported as failed, only because the result line
was weird / unexpected. No great robust way to parse this, but I changed it
to look explicitly for |Pass or |Fail and use those positions as anchor points.
