Auto merge of #13058 - malisas:malisa-responseAPI, r=Manishearth,jdm

Response API

<!-- Please describe your changes on the following line: -->
This PR adds the [dom::Response](https://fetch.spec.whatwg.org/#response-class) implementation and addresses #11896.

The relevant passing tests` expectations have been updated.

In order to allow non-UTF-8-encoded status messages, `net_traits::response::Response`'s `raw_status` field has been changed from type [`Option<RawStatus>`](https://doc.servo.org/hyper/http/struct.RawStatus.html) to type `Option<(u16, Vec<u8>)>`. As a result, a few other files which rely on the `raw_status` field were affected and updated.

TODOs:
- The `body` and `trailer` methods. Relies on implementation of `ReadableStream` and `Promise`s.
- Similarly, replace the dummy constructor `_body: Option<USVString>` argument with `body: ResponseBodyInit`.
- Currently, whenever `r's response's header list` or `r's Headers object` are mentioned, I always modify the `headers_reflector` field (of type dom::Headers, or `r's Headers object`) and not the corresponding hyper::Headers list in the net_traits::Response field. A completely accurate interpretation of the spec might consider making both of these lists the same thing via a reference. [Discussion](https://github.com/whatwg/fetch/issues/358) was [had](https://github.com/servo/servo/pull/12884).

---
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- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [ ] These changes fix #__ (github issue number if applicable).

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- [X] There are tests for these changes OR
- [ ] These changes do not require tests because _____

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components/net/about_loader.rs

@@ -4,7 +4,6 @@
 
 use file_loader;
 use hyper::header::ContentType;
-use hyper::http::RawStatus;
 use hyper::mime::{Mime, SubLevel, TopLevel};
 use hyper_serde::Serde;
 use mime_classifier::MimeClassifier;
@@ -38,7 +37,7 @@ pub fn factory(mut load_data: LoadData,
                     Some(Serde(ContentType(Mime(TopLevel::Text, SubLevel::Html, vec![])))),
                 charset: Some("utf-8".to_owned()),
                 headers: None,
-                status: Some(Serde(RawStatus(200, "OK".into()))),
+                status: Some((200, b"OK".to_vec())),
                 https_state: HttpsState::None,
                 referrer: None,
             };

components/net/blob_loader.rs

@@ -5,7 +5,6 @@
 use filemanager_thread::{FileManager, UIProvider};
 use hyper::header::{DispositionType, ContentDisposition, DispositionParam};
 use hyper::header::{Headers, ContentType, ContentLength, Charset};
-use hyper::http::RawStatus;
 use hyper_serde::Serde;
 use ipc_channel::ipc;
 use mime::{Mime, Attr};
@@ -72,7 +71,7 @@ fn load_blob<UI: 'static + UIProvider>
                     charset: charset.map(|c| c.as_str().to_string()),
                     headers: Some(Serde(headers)),
                     // https://w3c.github.io/FileAPI/#TwoHundredOK
-                    status: Some(Serde(RawStatus(200, "OK".into()))),
+                    status: Some((200, b"OK".to_vec())),
                     https_state: HttpsState::None,
                     referrer: None,
                 };

components/net/fetch/methods.rs

@@ -973,8 +973,9 @@ fn http_network_fetch(request: Rc<Request>,
         Ok((res, msg)) => {
             response.url = Some(url.clone());
             response.status = Some(res.response.status);
-            response.raw_status = Some(res.response.status_raw().clone());
-            response.headers = res.response.headers.clone();
+            response.raw_status = Some((res.response.status_raw().0,
+                                        res.response.status_raw().1.as_bytes().to_vec()));
+                        response.headers = res.response.headers.clone();
 
             let res_body = response.body.clone();
 
@@ -1001,7 +1002,7 @@ fn http_network_fetch(request: Rc<Request>,
                                 send_response_to_devtools(
                                     &sender, request_id.unwrap(),
                                     meta_headers.map(Serde::into_inner),
-                                    meta_status.map(Serde::into_inner),
+                                    meta_status,
                                     pipeline_id);
                             }
                         }

components/net/http_loader.rs

@@ -629,7 +629,7 @@ pub fn send_request_to_devtools(msg: ChromeToDevtoolsControlMsg,
 pub fn send_response_to_devtools(devtools_chan: &Sender<DevtoolsControlMsg>,
                              request_id: String,
                              headers: Option<Headers>,
-                             status: Option<RawStatus>,
+                             status: Option<(u16, Vec<u8>)>,
                              pipeline_id: PipelineId) {
     let response = DevtoolsHttpResponse { headers: headers, status: status, body: None, pipeline_id: pipeline_id };
     let net_event_response = NetworkEvent::HttpResponse(response);
@@ -1081,7 +1081,8 @@ pub fn load<A, B>(load_data: &LoadData,
             None => None
         });
         metadata.headers = Some(Serde(adjusted_headers));
-        metadata.status = Some(Serde(response.status_raw().clone()));
+        metadata.status = Some((response.status_raw().0,
+                                response.status_raw().1.as_bytes().to_vec()));
         metadata.https_state = if doc_url.scheme() == "https" {
             HttpsState::Modern
         } else {
@@ -1097,7 +1098,7 @@ pub fn load<A, B>(load_data: &LoadData,
                 send_response_to_devtools(
                     &chan, request_id.unwrap(),
                     metadata.headers.clone().map(Serde::into_inner),
-                    metadata.status.clone().map(Serde::into_inner),
+                    metadata.status.clone(),
                     pipeline_id);
             }
         }