This makes Fetch rely less on using main_thread_vm().current_realm(),
which relies on the dummy execution context if no JavaScript is
currently running.
The majority of error strings are StringView literals, and it seems
silly to require heap-allocating strings for these.
This idea is stolen from a recent change in fd1fbad :^)
Since BodyInit and Headers are tightly coupled to both Request and
Response, I chose to do all of them at once instead of introducing a
bunch of temporary conversion glue code.
Note that as of this commit, there aren't any such throwers, and the
call site in Heap::allocate will drop exceptions on the floor. This
commit only serves to change the declaration of the overrides, make sure
they return an empty value, and to propagate OOM errors frm their base
initialize invocations.
This needs to happen before prototype/constructor intitialization can be
made lazy. Otherwise, GC could run during the C++ constructor and try to
collect the object currently being created.
Move the macro to LibJS and change it to return a throw completion
instead of a WebIDL exception. This will let us use this macro within
LibJS to handle OOM conditions.
We have a new, improved string type coming up in AK (OOM aware, no null
state), and while it's going to use UTF-8, the name UTF8String is a
mouthful - so let's free up the String name by renaming the existing
class.
Making the old one have an annoying name will hopefully also help with
quick adoption :^)
There will be a lot of different cases where we'll return an error
response, and having a customized Promise rejection message seems quite
useful.
Note that this has to be distinct from the existing 'status message',
which is required to be empty in those cases.
This is the way.
On a more serious note, there's no reason to keep adding ref-counted
classes to LibWeb now that the majority of classes is GC'd - it only
adds the risk of discovering some cycle down the line, and forces us to
use handles as we can't visit().
This allows us to use this:
```cpp
auto header = TRY_OR_RETURN_OOM(realm,
Infrastructure::Header::from_string_pair(name, value));
```
Instead of the somewhat unwieldly:
```cpp
auto header = Infrastructure::Header {
.name = TRY_OR_RETURN_OOM(realm, ByteBuffer::copy(name.bytes())),
.value = TRY_OR_RETURN_OOM(realm, ByteBuffer::copy(value.bytes())),
};
```
With the addition of the 'fetch params' struct, the single ownership
model we had so far falls apart completely.
Additionally, this works nicely for FilteredResponse's internal response
instead of risking a dangling reference.
Replacing the public constructor with a create() function also found a
few instances of a Request being stack-allocated!
