Implement the new Sync Confirmation dialog on Linux and Windows.

chrome/browser/ui/cocoa/browser_window_cocoa.h

Index: chrome/browser/ui/cocoa/browser_window_cocoa.h
diff --git a/chrome/browser/ui/cocoa/browser_window_cocoa.h b/chrome/browser/ui/cocoa/browser_window_cocoa.h
index e6b9d2e481c49deecb4a04a6564cf6bc6850a2dd..d4e44a071ec50d6f7a467cd3e013a7232042107e 100644
--- a/chrome/browser/ui/cocoa/browser_window_cocoa.h
+++ b/chrome/browser/ui/cocoa/browser_window_cocoa.h
@@ -161,6 +161,7 @@ class BrowserWindowCocoa
       const signin::ManageAccountsParams& manage_accounts_params) override;
   void ShowModalSigninWindow(AvatarBubbleMode mode) override;
   void CloseModalSigninWindow() override;
+  void ShowModalSyncConfirmationWindow();
   int GetRenderViewHeightInsetWithDetachedBookmarkBar() override;
   void ExecuteExtensionCommand(const extensions::Extension* extension,
                                const extensions::Command& command) override;