Sets transient for PrintDialogGtk2

chrome/browser/ui/libgtk2ui/print_dialog_gtk2.h

Index: chrome/browser/ui/libgtk2ui/print_dialog_gtk2.h
diff --git a/chrome/browser/ui/libgtk2ui/print_dialog_gtk2.h b/chrome/browser/ui/libgtk2ui/print_dialog_gtk2.h
index d314842ca7a48b4db6fb23df95ed95f96e1e7041..ecbb6ec018f7f8c5923ae46bc3cfda1570ae539a 100644
--- a/chrome/browser/ui/libgtk2ui/print_dialog_gtk2.h
+++ b/chrome/browser/ui/libgtk2ui/print_dialog_gtk2.h
@@ -16,6 +16,7 @@
 #include "content/public/browser/browser_thread.h"
 #include "printing/print_dialog_gtk_interface.h"
 #include "printing/printing_context_linux.h"
+#include "ui/aura/window_observer.h"
 
 namespace printing {
 class Metafile;
@@ -28,7 +29,8 @@ using printing::PrintingContextLinux;
 class PrintDialogGtk2
     : public printing::PrintDialogGtkInterface,
       public base::RefCountedThreadSafe<
-          PrintDialogGtk2, content::BrowserThread::DeleteOnUIThread> {
+          PrintDialogGtk2, content::BrowserThread::DeleteOnUIThread>,
+      public aura::WindowObserver {
  public:
   // Creates and returns a print dialog.
   static printing::PrintDialogGtkInterface* CreatePrintDialog(
@@ -70,6 +72,9 @@ class PrintDialogGtk2
   // |settings|.
   void InitPrintSettings(printing::PrintSettings* settings);
 
+  // aura::WindowObserver implementation.
+  virtual void OnWindowDestroying(aura::Window* window) OVERRIDE;
+
   // Printing dialog callback.
   PrintingContextLinux::PrintSettingsCallback callback_;
   PrintingContextLinux* context_;