Provide mutable members of UrlRequestContext via pure-virtual interface

net/url_request/url_request_context_storage.cc

Index: net/url_request/url_request_context_storage.cc
diff --git a/net/url_request/url_request_context_storage.cc b/net/url_request/url_request_context_storage.cc
index 2a75db2f06e3fae334884285f29cb4d4f305a764..b0e9185273819dbcdd0a51f3be6310f957f09d04 100644
--- a/net/url_request/url_request_context_storage.cc
+++ b/net/url_request/url_request_context_storage.cc
@@ -122,4 +122,10 @@ void URLRequestContextStorage::set_throttler_manager(
   throttler_manager_.reset(throttler_manager);
 }
 
+void URLRequestContextStorage::set_http_user_agent_settings(
+    HttpUserAgentSettings* http_user_agent_settings) {
+  context_->set_http_user_agent_settings(http_user_agent_settings);
+  http_user_agent_settings_.reset(http_user_agent_settings);
+}
+
 }  // namespace net