[cros] disable GDrive option on certain file pickers

ui/base/dialogs/select_file_dialog_mac.mm

 // 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 "ui/base/dialogs/select_file_dialog.h"
 
 #import <Cocoa/Cocoa.h>
 #include <CoreServices/CoreServices.h>
 
 #include <map>
@@ skipping 217 matching lines @@
               CreateUTIFromExtension(ext_list[j]));
           [file_type_set addObject:base::mac::CFToNSCast(uti.get())];
         }
       }
       allowed_file_types = [file_type_set allObjects];
     }
     if (type == SELECT_SAVEAS_FILE)
       [dialog setAllowedFileTypes:allowed_file_types];
     // else we'll pass it in when we run the open panel
 
-    if (file_types->include_all_files)
+    if (file_types->include_all_files || file_types->extensions.empty())
       [dialog setAllowsOtherFileTypes:YES];
 
     if (file_types->extension_description_overrides.size() > 1) {
       NSView* accessory_view = GetAccessoryView(file_types, file_type_index);
       [dialog setAccessoryView:accessory_view];
     }
   } else {
     // If no type info is specified, anything goes.
     [dialog setAllowsOtherFileTypes:YES];
   }
@@ skipping 158 matching lines @@
 
 namespace ui {
 
 SelectFileDialog* CreateMacSelectFileDialog(
     SelectFileDialog::Listener* listener,
     SelectFilePolicy* policy) {
   return new SelectFileDialogImpl(listener, policy);
 }
 
 }  // namespace ui