Make Response's `Clone()` method to clone headers.

components/script/dom/response.rs

@@ -5,7 +5,7 @@
 use body::{BodyOperations, BodyType, consume_body, consume_body_with_promise};
 use core::cell::Cell;
 use dom::bindings::cell::DOMRefCell;
-use dom::bindings::codegen::Bindings::HeadersBinding::HeadersMethods;
+use dom::bindings::codegen::Bindings::HeadersBinding::{HeadersInit, HeadersMethods};
 use dom::bindings::codegen::Bindings::ResponseBinding;
 use dom::bindings::codegen::Bindings::ResponseBinding::{ResponseMethods, ResponseType as DOMResponseType};
 use dom::bindings::codegen::Bindings::XMLHttpRequestBinding::BodyInit;
@@ -303,6 +303,7 @@ impl ResponseMethods for Response {
         // Step 2
         let new_response = Response::new(&self.global());
         new_response.Headers().set_guard(self.Headers().get_guard());
+        try!(new_response.Headers().fill(Some(HeadersInit::Headers(self.Headers()))));
 
         // https://fetch.spec.whatwg.org/#concept-response-clone
         // Instead of storing a net_traits::Response internally, we

tests/wpt/metadata/fetch/api/response/response-clone.html.ini

@@ -1,8 +1,5 @@
 [response-clone.html]
   type: testharness
-  [Check Response's clone has the expected attribute values]
-    expected: FAIL
-
   [Check orginal response's body after cloning]
     expected: FAIL