Firefox overlay is seen opened even if Import Overlay is Cancelled.

chrome/browser/ui/views/importer/import_lock_dialog_view.h

Index: chrome/browser/ui/views/importer/import_lock_dialog_view.h
diff --git a/chrome/browser/ui/views/importer/import_lock_dialog_view.h b/chrome/browser/ui/views/importer/import_lock_dialog_view.h
index c69140a9c6a6691db284bbd791980c33cf77a3b9..38dd2ed5bb2ee8f244d1a456a33ca25679f2285a 100644
--- a/chrome/browser/ui/views/importer/import_lock_dialog_view.h
+++ b/chrome/browser/ui/views/importer/import_lock_dialog_view.h
@@ -10,6 +10,7 @@
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "ui/views/view.h"
+#include "ui/views/widget/widget_observer.h"
 #include "ui/views/window/dialog_delegate.h"
 
 namespace views {
@@ -18,10 +19,12 @@ class Label;
 
 // ImportLockDialogView asks the user to shut down Firefox before starting the
 // profile import.
-class ImportLockDialogView : public views::DialogDelegateView {
+class ImportLockDialogView : public views::DialogDelegateView,
+                             public views::WidgetObserver {
  public:
   static void Show(gfx::NativeWindow parent,
                    const base::Callback<void(bool)>& callback);
+  static void Hide();
 
  private:
   explicit ImportLockDialogView(const base::Callback<void(bool)>& callback);
@@ -37,6 +40,9 @@ class ImportLockDialogView : public views::DialogDelegateView {
   bool Accept() override;
   bool Cancel() override;
 
+  // views::WidgetObserver:
+  void OnWidgetDestroying(views::Widget* widget) override;
+
  private:
   views::Label* description_label_;