[Chromecast] Populate HTTP info for extension reqests, required for overlays

Bug: b/72506886
Test: load browser sample as an overlay
Change-Id: I69fd1e69e80f1c624508f77f745327acdb26e19c
Reviewed-on: https://chromium-review.googlesource.com/926970Reviewed-by: Luke Halliwell <halliwell@chromium.org>
Commit-Queue: Albert Chaulk <achaulk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#537896}

chromecast/browser/extension_request_protocol_handler.cc

@@ -155,7 +155,9 @@ bool CastExtensionURLRequestJob::GetCharset(std::string* charset) {
   return true;
 }
 
-void CastExtensionURLRequestJob::GetResponseInfo(net::HttpResponseInfo* info) {}
+void CastExtensionURLRequestJob::GetResponseInfo(net::HttpResponseInfo* info) {
+  *info = sub_request_->response_info();
+}
 
 void CastExtensionURLRequestJob::GetLoadTimingInfo(
     net::LoadTimingInfo* load_timing_info) const {