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

net/url_request/url_request.h

Index: net/url_request/url_request.h
diff --git a/net/url_request/url_request.h b/net/url_request/url_request.h
index 73e02d99c8710171d0c83c780eafabdcd1097645..aef6ae5729e939249f6d6ca3ca8d8feaa26f11da 100644
--- a/net/url_request/url_request.h
+++ b/net/url_request/url_request.h
@@ -356,6 +356,10 @@ class NET_EXPORT URLRequest : NON_EXPORTED_BASE(public base::NonThreadSafe),
     return extra_request_headers_;
   }
 
+  void set_default_user_agent(const std::string& default_user_agent);
+  const std::string& default_user_agent() const { return default_user_agent_; }
+  bool has_default_user_agent() const;
+
   // Gets the full request headers sent to the server.
   //
   // Return true and overwrites headers if it can get the request headers;
@@ -763,6 +767,8 @@ class NET_EXPORT URLRequest : NON_EXPORTED_BASE(public base::NonThreadSafe),
   std::string token_binding_referrer_;
   FirstPartyURLPolicy first_party_url_policy_;
   HttpRequestHeaders extra_request_headers_;
+  bool has_default_user_agent_;
+  std::string default_user_agent_;
   int load_flags_;  // Flags indicating the request type for the load;
                     // expected values are LOAD_* enums above.