Implement the new Sync Confirmation dialog on Linux and Windows.

chrome/browser/ui/cocoa/browser_window_cocoa.mm

Index: chrome/browser/ui/cocoa/browser_window_cocoa.mm
diff --git a/chrome/browser/ui/cocoa/browser_window_cocoa.mm b/chrome/browser/ui/cocoa/browser_window_cocoa.mm
index 64b2829fbf0dd63c6b1eca2d27093a702be20f77..931b5bbbd4a5c1ee0e486b4c6927275e71863d06 100644
--- a/chrome/browser/ui/cocoa/browser_window_cocoa.mm
+++ b/chrome/browser/ui/cocoa/browser_window_cocoa.mm
@@ -862,10 +862,15 @@ void BrowserWindowCocoa::ShowModalSigninWindow(
     signin_metrics::AccessPoint access_point) {
   NOTREACHED();
 }
+
 void BrowserWindowCocoa::CloseModalSigninWindow() {
   NOTREACHED();
 }
 
+void BrowserWindowCocoa::ShowModalSyncConfirmationWindow() {
+  NOTREACHED();
+}
+
 int
 BrowserWindowCocoa::GetRenderViewHeightInsetWithDetachedBookmarkBar() {
   if (browser_->bookmark_bar_state() != BookmarkBar::DETACHED)