Improve merging of header modifications in webRequest.OnHeadersReceived

net/url_request/url_request_http_job.h

Index: net/url_request/url_request_http_job.h
diff --git a/net/url_request/url_request_http_job.h b/net/url_request/url_request_http_job.h
index e84c51d86ad6e43ea05382b8e48ae691dcef2b11..2a0e7aca9bce1e0b09af3e5768b5ecda8f2fcfe5 100644
--- a/net/url_request/url_request_http_job.h
+++ b/net/url_request/url_request_http_job.h
@@ -220,6 +220,9 @@ class URLRequestHttpJob : public URLRequestJob {
 
   OldCompletionCallbackImpl<URLRequestHttpJob> on_headers_received_callback_;
 
+  // We allow the network delegate to modify a copy of the response headers.
+  // This prevents modifications of headers that are shared with the underlying
+  // layers of the network stack.
   scoped_refptr<HttpResponseHeaders> override_response_headers_;
 
   // Flag used to verify that |this| is not deleted while we are awaiting