Instead of creating an IPC channel for every fetch, allow cancelling
fetches based on the `RequestId` of the original request. This requires
that `RequestId`s be UUIDs so that they are unique between processes
that might communicating with the resource process.
In addition, the resource process loop now keeps a `HashMap` or `Weak`
handles to cancellers and cleans them up.
This allows for creating mutiple `FetchCanceller`s in `script` for a
single fetch request, allowing integration of the media and video
elements to integrate with the `Document` canceller list -- meaning
these fetches also get cancelled when the `Document` unloads.
Signed-off-by: Martin Robinson <mrobinson@igalia.com>
This allows reusing the asynchrnous fetch mechanism that we use for page
resources and is likely a step toward removing the `FetchThread`.
Benefits:
- Reduces IPC traffic during navigation. Now instead of bouncing
between the constellation and the `ScriptThread` responses are sent
directly to the `ScriptThread`.
- Allows cancelling loads after redirects, which was not possible
before.
There is the question of what to do when a redirect is cross-origin
(#23037). This currently isn't handled properly as the `Constellation`
sends data to the same `Pipeline` that initiated the load. This change
doesn't fix this issue, but does make it more possible for the
`ScriptThread` to shut down the pipeline and ask the `Constellation` to
replace it with a new one.
Signed-off-by: Martin Robinson <mrobinson@igalia.com>
