PPAPI: Add an API for setting a custom user agent for URL requests.

ppapi/shared_impl/ppb_url_request_info_shared.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 PPAPI_SHARED_IMPL_PPB_URL_REQUEST_INFO_SHARED_H_
 #define PPAPI_SHARED_IMPL_PPB_URL_REQUEST_INFO_SHARED_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 55 matching lines @@
   // set (or has been set to an Undefined Var) and the default referrer should
   // be used. (Setting the custom referrer to an empty string indicates that no
   // referrer header should be generated.)
   bool has_custom_referrer_url;
   std::string custom_referrer_url;
 
   bool allow_cross_origin_requests;
   bool allow_credentials;
 
   // Similar to the custom referrer (above), but for custom content transfer
-  // encoding.
+  // encoding and custom user agent, respectively.
   bool has_custom_content_transfer_encoding;
   std::string custom_content_transfer_encoding;
+  bool has_custom_user_agent;
+  std::string custom_user_agent;
 
   int32_t prefetch_buffer_upper_threshold;
   int32_t prefetch_buffer_lower_threshold;
 
   std::vector<BodyItem> body;
 
   // If you add more stuff here, be sure to modify the serialization rules in
   // ppapi_messages.h
 };
 
@@ skipping 36 matching lines @@
 
  private:
   PPB_URLRequestInfo_Data data_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(PPB_URLRequestInfo_Shared);
 };
 
 }  // namespace ppapi
 
 #endif  // PPAPI_SHARED_IMPL_PPB_URL_REQUEST_INFO_SHARED_H_