Delay generation of User-Agent header to URLRequestHttpJob and accept custom User-Agent from XHR/Fe…

content/child/request_info.h

Index: content/child/request_info.h
diff --git a/content/child/request_info.h b/content/child/request_info.h
index 4f453801eda8018fe632f0f18a3a39840ffcbb2f..7df4933ec7e06ffb8ab24dcd3b8f0a17a18b00df 100644
--- a/content/child/request_info.h
+++ b/content/child/request_info.h
@@ -58,6 +58,10 @@ struct CONTENT_EXPORT RequestInfo {
   // be null if no extra request headers need to be set.
   std::string headers;
 
+  // The User-Agent string specified by the renderer to send in case |headers|
+  // results to get no entry named "User-Agent".
+  std::string default_user_agent;
+
   // Composed of the values defined in url_request_load_flags.h.
   int load_flags;