Auto merge of #26881 - gterzian:fix_streams_and_re-direct, r=jdm

Fix re-extracting stream upon re-direct

<!-- Please describe your changes on the following line: -->

This fixes the logic in `net` regarding re-extracting a stream from the request body as part of a re-direct.

The problem was that the `read_from` flag was never read as `true`, because it would be set on the clone of the original request used in the http fech, and the original request would then be used for the re-direct. So the original request never had a `read_from` flag set to true.

Also, this removes the entire `read_from` concept, and instead uses a spec-compliant hook to re-extract the stream, which doesn't require tracking whether the stream has been read from in another http fetch.

This will unblock https://github.com/servo/servo/pull/26810. I don't expect test changes in this one, although I have verified locally(using the other branch), that this fixes the issue that has emerged as part of that PR.

---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `___` with appropriate data: -->
- [ ] `./mach build -d` does not report any errors
- [ ] `./mach test-tidy` does not report any errors
- [ ] These changes fix #___ (GitHub issue number if applicable)

<!-- Either: -->
- [ ] There are tests for these changes OR
- [ ] These changes do not require tests because ___

<!-- Also, please make sure that "Allow edits from maintainers" checkbox is checked, so that we can help you if you get stuck somewhere along the way.-->

<!-- Pull requests that do not address these steps are welcome, but they will require additional verification as part of the review process. -->

components/net/http_loader.rs

@@ -911,8 +911,8 @@ pub fn http_redirect_fetch(
     }
 
     // Step 12
-    if let Some(_) = request.body {
-        // TODO: extract request's body's source
+    if let Some(body) = request.body.as_mut() {
+        body.extract_source();
     }
 
     // Step 13

components/net_traits/request.rs

@@ -142,8 +142,6 @@ pub struct RequestBody {
     /// Net's channel to communicate with script re this body.
     #[ignore_malloc_size_of = "Channels are hard"]
     chan: IpcSender<BodyChunkRequest>,
-    /// Has the stream been read from already?
-    read_from: bool,
     /// <https://fetch.spec.whatwg.org/#concept-body-source>
     source: BodySource,
     /// <https://fetch.spec.whatwg.org/#concept-body-total-bytes>
@@ -160,25 +158,22 @@ impl RequestBody {
             chan,
             source,
             total_bytes,
-            read_from: false,
+        }
+    }
+
+    /// Step 12 of https://fetch.spec.whatwg.org/#concept-http-redirect-fetch
+    pub fn extract_source(&mut self) {
+        match self.source {
+            BodySource::Null => panic!("Null sources should never be re-directed."),
+            BodySource::Object => {
+                let (chan, port) = ipc::channel().unwrap();
+                let _ = self.chan.send(BodyChunkRequest::Extract(port));
+                self.chan = chan.clone();
+            },
         }
     }
 
     pub fn take_stream(&mut self) -> IpcSender<BodyChunkRequest> {
-        if self.read_from {
-            match self.source {
-                BodySource::Null => panic!(
-                    "Null sources should never be read more than once(no re-direct allowed)."
-                ),
-                BodySource::Object => {
-                    let (chan, port) = ipc::channel().unwrap();
-                    let _ = self.chan.send(BodyChunkRequest::Extract(port));
-                    self.chan = chan.clone();
-                    return chan;
-                },
-            }
-        }
-        self.read_from = true;
         self.chan.clone()
     }