[ios clean] Add placeholder for NTP bookmarks, chrome home and open tabs.

ios/clean/chrome/browser/ui/web_contents/web_contents_mediator.mm

Index: ios/clean/chrome/browser/ui/web_contents/web_contents_mediator.mm
diff --git a/ios/clean/chrome/browser/ui/web_contents/web_contents_mediator.mm b/ios/clean/chrome/browser/ui/web_contents/web_contents_mediator.mm
index 2a5529bc5f8dd067bc843f649c472665d58b8d77..713db4550b17f03d3c7382aa67b0538e610da031 100644
--- a/ios/clean/chrome/browser/ui/web_contents/web_contents_mediator.mm
+++ b/ios/clean/chrome/browser/ui/web_contents/web_contents_mediator.mm
@@ -4,6 +4,7 @@
 
 #import "ios/clean/chrome/browser/ui/web_contents/web_contents_mediator.h"
 
+#include "ios/chrome/browser/chrome_url_constants.h"
 #import "ios/clean/chrome/browser/ui/web_contents/web_contents_consumer.h"
 #import "ios/web/public/navigation_manager.h"
 #include "ios/web/public/web_state/web_state.h"
@@ -28,8 +29,7 @@
 
   self.webState->SetWebUsageEnabled(true);
   if (!self.webState->GetNavigationManager()->GetItemCount()) {
-    web::NavigationManager::WebLoadParams params(
-        GURL("https://dev.chromium.org/"));
+    web::NavigationManager::WebLoadParams params((GURL(kChromeUINewTabURL)));
     params.transition_type = ui::PAGE_TRANSITION_TYPED;
     self.webState->GetNavigationManager()->LoadURLWithParams(params);
   }