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

net/url_request/url_request.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef NET_URL_REQUEST_URL_REQUEST_H_
 #define NET_URL_REQUEST_URL_REQUEST_H_
 
 #include <stdint.h>
 
 #include <memory>
@@ skipping 338 matching lines @@
 
   // Sets all extra request headers.  Any extra request headers set by other
   // methods are overwritten by this method.  This method may only be called
   // before Start() is called.  It is an error to call it later.
   void SetExtraRequestHeaders(const HttpRequestHeaders& headers);
 
   const HttpRequestHeaders& extra_request_headers() const {
     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;
   // otherwise, returns false and does not modify headers.  (Always returns
   // false for request types that don't have headers, like file requests.)
   //
   // This is guaranteed to succeed if:
   //
   // 1. A redirect or auth callback is currently running.  Once it ends, the
   //    headers may become unavailable as a new request with the new address
@@ skipping 387 matching lines @@
   std::vector<GURL> url_chain_;
   GURL first_party_for_cookies_;
   url::Origin initiator_;
   GURL delegate_redirect_url_;
   std::string method_;  // "GET", "POST", etc. Should be all uppercase.
   std::string referrer_;
   ReferrerPolicy referrer_policy_;
   std::string token_binding_referrer_;
   FirstPartyURLPolicy first_party_url_policy_;
   HttpRequestHeaders extra_request_headers_;
+  bool has_default_user_agent_;

[horo, 2016/08/21 08:39:37]

You can use base::Optional<std::string>.

[mmenke, 2016/08/21 14:37:39]

Given that URLRequest uses empty strings to denote arguments it should ignore,
I'd say just stick with an empty string, for consistency.

+  std::string default_user_agent_;
   int load_flags_;  // Flags indicating the request type for the load;
                     // expected values are LOAD_* enums above.
 
   // Never access methods of the |delegate_| directly. Always use the
   // Notify... methods for this.
   Delegate* delegate_;
 
   // Current error status of the job. When no error has been encountered, this
   // will be SUCCESS. If multiple errors have been encountered, this will be
   // the first non-SUCCESS status seen.
@@ skipping 71 matching lines @@
 
   // The proxy server used for this request, if any.
   HostPortPair proxy_server_;
 
   DISALLOW_COPY_AND_ASSIGN(URLRequest);
 };
 
 }  // namespace net
 
 #endif  // NET_URL_REQUEST_URL_REQUEST_H_