Fix a crash on clicking "Load unpacked extension" multiple times

chrome/browser/ui/libgtk2ui/select_file_dialog_impl_gtk2.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <gtk/gtk.h>
 #include <map>
 #include <set>
 #include <vector>
 
 // Xlib defines RootWindow
@@ skipping 210 matching lines @@
     const FileTypeInfo* file_types,
     int file_type_index,
     const base::FilePath::StringType& default_extension,
     gfx::NativeWindow owning_window,
     void* params) {
   type_ = type;
   // |owning_window| can be null when user right-clicks on a downloadable item
   // and chooses 'Open Link in New Tab' when 'Ask where to save each file
   // before downloading.' preference is turned on. (http://crbug.com/29213)
   if (owning_window) {
+    if (IsRunning(owning_window)) {
+      LOG(ERROR) << "Select file dialog already in use!";
+      return;

[Devlin, 2014/12/04 20:00:14]

This isn't what I was referring to.  I meant an early return in the
LoaderHandler, since there's already a dialog up.  I don't think that making a
platform-specific change is the right solution to this.

+    }
     owning_window->AddObserver(this);
     parents_.insert(owning_window);
   }
 
   std::string title_string = base::UTF16ToUTF8(title);
 
   file_type_index_ = file_type_index;
   if (file_types)
     file_types_ = *file_types;
 
@@ skipping 386 matching lines @@
   g_free(filename);
   if (pixbuf) {
     gtk_image_set_from_pixbuf(GTK_IMAGE(preview_), pixbuf);
     g_object_unref(pixbuf);
   }
   gtk_file_chooser_set_preview_widget_active(GTK_FILE_CHOOSER(chooser),
                                              pixbuf ? TRUE : FALSE);
 }
 
 }  // namespace libgtk2ui