Reland "Use the same browser instance in the sync confirmation dialog.

chrome/browser/ui/webui/signin/sync_confirmation_ui.h

 // Copyright 2015 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.
 
 #ifndef CHROME_BROWSER_UI_WEBUI_SIGNIN_SYNC_CONFIRMATION_UI_H_
 #define CHROME_BROWSER_UI_WEBUI_SIGNIN_SYNC_CONFIRMATION_UI_H_
 
 #include <memory>
 
 #include "base/macros.h"
 #include "ui/web_dialogs/web_dialog_ui.h"
 
 class SyncConfirmationHandler;
 
 namespace ui {
 class WebUI;
 }
 
+class Browser;
+
+// WebUI controller for the sync confirmation dialog.
+//
+// Note: This controller does not set the WebUI message handler. It is
+// the responsability of the caller to pass the correct message handler.
 class SyncConfirmationUI : public ui::WebDialogUI {
  public:
   explicit SyncConfirmationUI(content::WebUI* web_ui);
-   // Used to inject a SyncConfirmationHandler in tests.
-  SyncConfirmationUI(content::WebUI* web_ui,
-                     std::unique_ptr<SyncConfirmationHandler> handler);
   ~SyncConfirmationUI() override {}
 
+  // Initializes a SyncConfirmationHandler for |browser| and adds it to
+  // |web_ui()|.
+  void InitializeMessageHandlerWithBrowser(Browser* browser);
+
   DISALLOW_COPY_AND_ASSIGN(SyncConfirmationUI);
 };
 
 #endif  // CHROME_BROWSER_UI_WEBUI_SIGNIN_SYNC_CONFIRMATION_UI_H_