Add --use-more-webui runtime flag to toggle WebUI replacements for native dialogs.

chrome/browser/ui/webui/chrome_web_ui.cc

 // Copyright (c) 2011 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.
 
 #include "chrome/browser/ui/webui/chrome_web_ui.h"
 
 #include "chrome/browser/profiles/profile.h"
 #include "content/browser/tab_contents/tab_contents.h"
 
+namespace {
+
+// Set to true if we prefer using webui implementations over native.
+bool use_more_webui = false;
+}
+
 ChromeWebUI::ChromeWebUI(TabContents* contents)
     : WebUI(contents),
       force_bookmark_bar_visible_(false) {
 }
 
 ChromeWebUI::~ChromeWebUI() {
 }
 
 Profile* ChromeWebUI::GetProfile() const {
   return Profile::FromBrowserContext(tab_contents()->browser_context());
 }
+
+// static
+void ChromeWebUI::SetMoreWebUI(bool more_webui) {
+  use_more_webui = more_webui;
+}
+
+// static
+bool ChromeWebUI::IsMoreWebUI() {
+  return use_more_webui;
+}