Use devtools to set user agent in chromedriver

chrome/test/chromedriver/chrome/devtools_http_client.cc

Index: chrome/test/chromedriver/chrome/devtools_http_client.cc
diff --git a/chrome/test/chromedriver/chrome/devtools_http_client.cc b/chrome/test/chromedriver/chrome/devtools_http_client.cc
index b9c47087f3abf4dd1c8bf5cbcf8e20712e6d273c..c11e86d7461ec16bb310382da2dafdbe5a3ca0e2 100644
--- a/chrome/test/chromedriver/chrome/devtools_http_client.cc
+++ b/chrome/test/chromedriver/chrome/devtools_http_client.cc
@@ -71,7 +71,8 @@ DevToolsHttpClient::DevToolsHttpClient(
     const SyncWebSocketFactory& socket_factory,
     std::unique_ptr<DeviceMetrics> device_metrics,
     std::unique_ptr<std::set<WebViewInfo::Type>> window_types,
-    std::string page_load_strategy)
+    std::string page_load_strategy,
+    std::string user_agent)
     : context_getter_(context_getter),
       socket_factory_(socket_factory),
       server_url_("http://" + address.ToString()),
@@ -79,7 +80,8 @@ DevToolsHttpClient::DevToolsHttpClient(
                                                 address.ToString().c_str())),
       device_metrics_(std::move(device_metrics)),
       window_types_(std::move(window_types)),
-      page_load_strategy_(page_load_strategy) {
+      page_load_strategy_(page_load_strategy),
+      user_agent_(user_agent) {
   window_types_->insert(WebViewInfo::kPage);
   window_types_->insert(WebViewInfo::kApp);
 }
@@ -157,6 +159,10 @@ const DeviceMetrics* DevToolsHttpClient::device_metrics() {
   return device_metrics_.get();
 }
 
+const std::string& DevToolsHttpClient::user_agent() const {
+  return user_agent_;
+}
+
 bool DevToolsHttpClient::IsBrowserWindow(const WebViewInfo& view) const {
   return base::ContainsKey(*window_types_, view.type) ||
          (view.type == WebViewInfo::kOther &&
@@ -204,7 +210,7 @@ Status DevToolsHttpClient::CloseFrontends(const std::string& for_client_id) {
         socket_factory_, web_socket_url_prefix_ + *it, *it));
     std::unique_ptr<WebViewImpl> web_view(
         new WebViewImpl(*it, false, &browser_info_, std::move(client), NULL,
-                        page_load_strategy_));
+                        page_load_strategy_, user_agent_));
 
     status = web_view->ConnectIfNecessary();
     // Ignore disconnected error, because the debugger might have closed when