Replace requirePageReconstruction with setCustomUserAgent

ios/web/web_state/ui/crw_web_controller.h

Index: ios/web/web_state/ui/crw_web_controller.h
diff --git a/ios/web/web_state/ui/crw_web_controller.h b/ios/web/web_state/ui/crw_web_controller.h
index b7706278b98e7d772674bceb418ae1ce6dd2c5d0..0b22741099f2c768db206dd405efb8dcaf29fef9 100644
--- a/ios/web/web_state/ui/crw_web_controller.h
+++ b/ios/web/web_state/ui/crw_web_controller.h
@@ -191,14 +191,6 @@ class WebStateImpl;
 // Dismisses the soft keyboard.
 - (void)dismissKeyboard;
 
-// Requires that the next load rebuild the UIWebView. This is expensive, and
-// should be used only in the case where something has changed that UIWebView
-// only checks on creation, such that the whole object needs to be rebuilt.
-// TODO(stuartmorgan): Merge this and reinitializeWebViewAndReload:. They are
-// currently subtly different in terms of implementation, but are for
-// fundamentally the same purpose.
-- (void)requirePageReconstruction;
-
 - (void)reinitializeWebViewAndReload:(BOOL)reload;
 
 // Requires that the next display reload the page, using a placeholder while