Fix content-type when creating a Request with FormData body (#36194)

When you create a `Request` object with a `FormData` body, the spec
says that the `Content-Type` header should start with
`multipart/form-data; boundary=`. However, in Servo's implementation
it started with `multipart/form-data;boundary=`, without the space.

While all reasonable servers should be able to that headers whether
the space is present or not, this brings Servo closer to the spec, and
also makes some WPT tests pass.

Note that submitting a form with `enctype="multipart/form-data"` does
produce a `Content-Type` header with the space (see
`HTMLFormElement::submit_entity_body`).

Signed-off-by: Andreu Botella <abotella@igalia.com>

components/script/body.rs

@@ -539,7 +539,7 @@ impl Extractable for FormData {
         let bytes = encode_multipart_form_data(&mut self.datums(), boundary.clone(), UTF_8);
         let total_bytes = bytes.len();
         let content_type = Some(DOMString::from(format!(
-            "multipart/form-data;boundary={}",
+            "multipart/form-data; boundary={}",
             boundary
         )));
         let stream = ReadableStream::new_from_bytes(global, bytes, can_gc)?;

tests/wpt/meta/fetch/api/basic/request-headers.any.js.ini

@@ -5,16 +5,10 @@
   expected: ERROR
 
 [request-headers.any.html]
-  [Fetch with POST with FormData body]
-    expected: FAIL
-
   [Fetch with POST with Float16Array body]
     expected: FAIL
 
 
 [request-headers.any.worker.html]
-  [Fetch with POST with FormData body]
-    expected: FAIL
-
   [Fetch with POST with Float16Array body]
     expected: FAIL

tests/wpt/meta/fetch/api/request/request-init-contenttype.any.js.ini

@@ -1,8 +0,0 @@
-[request-init-contenttype.any.worker.html]
-  [Default Content-Type for Request with FormData body]
-    expected: FAIL
-
-
-[request-init-contenttype.any.html]
-  [Default Content-Type for Request with FormData body]
-    expected: FAIL

tests/wpt/meta/fetch/api/response/response-consume.html.ini

@@ -16,3 +16,6 @@
 
   [Consume response's body: from multipart form data blob to formData]
     expected: FAIL
+
+  [Consume response's body: from FormData to blob]
+    expected: FAIL

tests/wpt/meta/fetch/api/response/response-init-contenttype.any.js.ini

@@ -1,8 +0,0 @@
-[response-init-contenttype.any.worker.html]
-  [Default Content-Type for Response with FormData body]
-    expected: FAIL
-
-
-[response-init-contenttype.any.html]
-  [Default Content-Type for Response with FormData body]
-    expected: FAIL

tests/wpt/meta/fetch/content-length/api-and-duplicate-headers.any.js.ini

@@ -6,3 +6,6 @@
 [api-and-duplicate-headers.any.worker.html]
   [XMLHttpRequest and duplicate Content-Length/Content-Type headers]
     expected: FAIL
+
+  [fetch() and duplicate Content-Length/Content-Type headers]
+    expected: FAIL

tests/wpt/meta/xhr/setrequestheader-content-type.htm.ini

@@ -8,8 +8,5 @@
   [HTML Document request keeps setRequestHeader() Content-Type, with charset adjusted to UTF-8]
     expected: FAIL
 
-  [FormData request has correct default Content-Type of "multipart/form-data; boundary=_"]
-    expected: FAIL
-
   [URLSearchParams request keeps setRequestHeader() Content-Type, with charset adjusted to UTF-8]
     expected: FAIL