Use devtools to set user agent in chromedriver

chrome/test/chromedriver/chrome/web_view_impl.cc

Index: chrome/test/chromedriver/chrome/web_view_impl.cc
diff --git a/chrome/test/chromedriver/chrome/web_view_impl.cc b/chrome/test/chromedriver/chrome/web_view_impl.cc
index c55d72256256000c31a2f3af083e772065a3b9d7..dceae101ee2f49f68cfe905381cf556200a7aeca 100644
--- a/chrome/test/chromedriver/chrome/web_view_impl.cc
+++ b/chrome/test/chromedriver/chrome/web_view_impl.cc
@@ -129,18 +129,22 @@ WebViewImpl::WebViewImpl(const std::string& id,
                          const BrowserInfo* browser_info,
                          std::unique_ptr<DevToolsClient> client,
                          const DeviceMetrics* device_metrics,
-                         std::string page_load_strategy)
+                         std::string page_load_strategy,
+                         std::string user_agent)
     : id_(id),
       w3c_compliant_(w3c_compliant),
       browser_info_(browser_info),
       dom_tracker_(new DomTracker(client.get())),
       frame_tracker_(new FrameTracker(client.get())),
       dialog_manager_(new JavaScriptDialogManager(client.get())),
-      navigation_tracker_(PageLoadStrategy::Create(
-          page_load_strategy, client.get(),
-          browser_info, dialog_manager_.get())),
+      navigation_tracker_(PageLoadStrategy::Create(page_load_strategy,
+                                                   client.get(),
+                                                   browser_info,
+                                                   dialog_manager_.get())),
       mobile_emulation_override_manager_(
-          new MobileEmulationOverrideManager(client.get(), device_metrics)),
+          new MobileEmulationOverrideManager(client.get(),
+                                             device_metrics,
+                                             user_agent)),
       geolocation_override_manager_(
           new GeolocationOverrideManager(client.get())),
       network_conditions_override_manager_(