Auto merge of #13882 - jeenalee:response-clone, r=jdm

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

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This patch allows the response clone to have the same headers list as the original's. Previously, only the cloned response's headers guard was set to be the same as the original response's headers guard.

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- [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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1 files changed, 2 insertions, 1 deletions

diff --git a/components/script/dom/response.rs b/components/script/dom/response.rs
index cabbd567b49..a1226204418 100644
--- a/components/script/dom/response.rs
+++ b/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