Implement the new Sync Confirmation dialog on Linux and Windows.

chrome/test/base/test_browser_window.h

Index: chrome/test/base/test_browser_window.h
diff --git a/chrome/test/base/test_browser_window.h b/chrome/test/base/test_browser_window.h
index ebe738694d7931d54e800470a1413578a3a8d678..a0844289d3fb5a4fa962ef46639887b682acec6f 100644
--- a/chrome/test/base/test_browser_window.h
+++ b/chrome/test/base/test_browser_window.h
@@ -150,6 +150,7 @@ class TestBrowserWindow : public BrowserWindow {
       const signin::ManageAccountsParams& manage_accounts_params) override {}
   void ShowModalSigninWindow(AvatarBubbleMode mode) override {}
   void CloseModalSigninWindow() override {}
+  void ShowModalSyncConfirmationWindow() override {}
   int GetRenderViewHeightInsetWithDetachedBookmarkBar() override;
   void ExecuteExtensionCommand(const extensions::Extension* extension,
                                const extensions::Command& command) override;