Replace requirePageReconstruction with setCustomUserAgent

ios/web/web_view_creation_util.mm

Index: ios/web/web_view_creation_util.mm
diff --git a/ios/web/web_view_creation_util.mm b/ios/web/web_view_creation_util.mm
index d3023e0624ff7f6a857171e1db30a57eb049eacd..0edd5c4050ce67b11d7fe20701e6f3d1e20a18ee 100644
--- a/ios/web/web_view_creation_util.mm
+++ b/ios/web/web_view_creation_util.mm
@@ -5,6 +5,7 @@
 #import "ios/web/public/web_view_creation_util.h"
 
 #include "base/logging.h"
+#include "ios/web/public/user_agent.h"
 #import "ios/web/web_state/ui/wk_web_view_configuration_provider.h"
 #import "ios/web/web_state/web_view_internal_creation_util.h"
 
@@ -27,7 +28,8 @@
   WKWebViewConfigurationProvider& config_provider =
       WKWebViewConfigurationProvider::FromBrowserState(browser_state);
   return BuildWKWebView(frame, config_provider.GetWebViewConfiguration(),
-                        browser_state, NO, context_menu_delegate);
+                        browser_state, UserAgentType::MOBILE,
+                        context_menu_delegate);
 }
 
 }  // namespace web