Use devtools to set user agent in chromedriver

chrome/test/chromedriver/chrome/mobile_emulation_override_manager.h

 // Copyright 2014 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 CHROME_TEST_CHROMEDRIVER_CHROME_MOBILE_EMULATION_OVERRIDE_MANAGER_H_
 #define CHROME_TEST_CHROMEDRIVER_CHROME_MOBILE_EMULATION_OVERRIDE_MANAGER_H_
 
 #include <memory>
 #include <string>
 
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "chrome/test/chromedriver/chrome/devtools_event_listener.h"
 
 namespace base {
 class DictionaryValue;
 }
 
 class DevToolsClient;
 struct DeviceMetrics;
 class Status;
 
 // Overrides the device metrics, if requested, for the duration of the
 // given |DevToolsClient|'s lifetime.
 class MobileEmulationOverrideManager : public DevToolsEventListener {
  public:
   MobileEmulationOverrideManager(DevToolsClient* client,
-                                 const DeviceMetrics* device_metrics);
+                                 const DeviceMetrics* device_metrics,
+                                 std::string user_agent);
   ~MobileEmulationOverrideManager() override;
 
   // Overridden from DevToolsEventListener:
   Status OnConnected(DevToolsClient* client) override;
   Status OnEvent(DevToolsClient* client,
                  const std::string& method,
                  const base::DictionaryValue& params) override;
 
   bool IsEmulatingTouch();
 
  private:
   Status ApplyOverrideIfNeeded();
 
   DevToolsClient* client_;
   const DeviceMetrics* overridden_device_metrics_;
+  const std::string overridden_user_agent_;
 
   DISALLOW_COPY_AND_ASSIGN(MobileEmulationOverrideManager);
 };
 
 #endif  // CHROME_TEST_CHROMEDRIVER_CHROME_MOBILE_EMULATION_OVERRIDE_MANAGER_H_