Implement the new Sync Confirmation dialog on Linux and Windows.

chrome/browser/ui/browser_window.h

Index: chrome/browser/ui/browser_window.h
diff --git a/chrome/browser/ui/browser_window.h b/chrome/browser/ui/browser_window.h
index b334c083c5d17408c0ea3d18c63245a7421d58e9..b85e07fdd63ca3c14bf7bb65710a110a2fab5007 100644
--- a/chrome/browser/ui/browser_window.h
+++ b/chrome/browser/ui/browser_window.h
@@ -394,6 +394,11 @@ class BrowserWindow : public ui::BaseWindow {
   // open. Does nothing otherwise.
   virtual void CloseModalSigninWindow() = 0;
 
+  // Shows the tab modal sync confirmation dialog that informs the user about
+  // sync and gives them a chance to abort signin under the tab modal signin
+  // flow.
+  virtual void ShowModalSyncConfirmationWindow() = 0;
+
   // Returns the height inset for RenderView when detached bookmark bar is
   // shown.  Invoked when a new RenderHostView is created for a non-NTP
   // navigation entry and the bookmark bar is detached.