This interface is used to display a confirmatino dialog before
 launching a "helper app" to handle content not handled by
 Mozilla.

 Usage:  Clients (of which there is one: the nsIExternalHelperAppService
 implementation in mozilla/uriloader/exthandler) create an instance of
 this interface (using the contract ID) and then call the show() method.

 The dialog is shown non-modally.  The implementation of the dialog
 will access methods of the nsIHelperAppLauncher passed in to show()
 in order to cause a "save to disk" or "open using" action.
[scriptable, uuid(f3704fdc-8ae6-4eba-a3c3-f02958ac0649)]
interface nsIHelperAppLauncherDialog : nsISupports

Constants

 This request is passed to the helper app dialog because Gecko can not
 handle content of this type.
const unsigned long REASON_CANTHANDLE = 0 
 The server requested external handling.
const unsigned long REASON_SERVERREQUEST = 1 
 Gecko detected that the type sent by the server (e.g. text/plain) does
 not match the actual type.
const unsigned long REASON_TYPESNIFFED = 2

Methods

 Invoke a save-to-file dialog instead of the full fledged helper app dialog.
 Returns the a nsILocalFile for the file name/location selected.

 @param aLauncher
        A nsIHelperAppLauncher to be invoked when a file is selected.
 @param aWindowContext
        Window associated with action.
 @param aDefaultFileName
        Default file name to provide (can be null)
 @param aSuggestedFileExtension
        Sugested file extension
 @param aForcePrompt
        Set to true to force prompting the user for thet file
        name/location, otherwise perferences may control if the user is
        prompted.
nsILocalFile promptForSaveToFile(in nsIHelperAppLauncher aLauncher, in nsISupports aWindowContext, in wstring aDefaultFileName, in wstring aSuggestedFileExtension, in boolean aForcePrompt) 
 Show confirmation dialog for launching application (or "save to
 disk") for content specified by aLauncher.

 @param aLauncher
        A nsIHelperAppLauncher to be invoked when a file is selected.
 @param aWindowContext
        Window associated with action.
 @param aReason
        One of the constants from above. It indicates why the dialog is
        shown. Implementors should treat unknown reasons like
        REASON_CANTHANDLE.
void show(in nsIHelperAppLauncher aLauncher, in nsISupports aWindowContext, in unsigned long aReason)