Bug #30157 --> add the ability to launch urls using OS default protocol handlers. (NOT PART OF THE BUILD)

code review will come when this is done and gets turned on.

Initial interface for interacting with an OS specific external protocol handler.

uriloader/exthandler/nsIExternalProtocolService.idl

@@ -0,0 +1,45 @@
+/* -*- Mode: C++; tab-width: 3; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ *
+ * The contents of this file are subject to the Mozilla Public
+ * License Version 1.1 (the "License"); you may not use this file
+ * except in compliance with the License. You may obtain a copy of
+ * the License at http://www.mozilla.org/MPL/
+ * 
+ * Software distributed under the License is distributed on an "AS
+ * IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
+ * implied. See the License for the specific language governing
+ * rights and limitations under the License.
+ * 
+ * The Original Code is the Mozilla browser.
+ * 
+ * The Initial Developer of the Original Code is Netscape
+ * Communications, Inc.  Portions created by Netscape are
+ * Copyright (C) 1999, Mozilla.  All Rights Reserved.
+ * 
+ * Contributor(s):
+ *   Scott MacGregor <mscott@netscape.com>
+ */
+
+/* The external protocol service is used for finding and launching
+   platform specific applications for particular protocols.
+
+   You can ask the external protocol service if it has an external
+   handler for a given protocol scheme. And you can ask it to load 
+   the url using the default handler...
+ */
+
+#include "nsISupports.idl"
+
+interface nsIURI;
+
+[scriptable, uuid(100FD4B3-4557-11d4-98D0-001083010E9B)]
+interface nsIExternalProtocolService : nsISupports
+{
+  // aProtocolScheme --> the scheme from a url: http, ftp, mailto, etc.
+  // returns true if we have a handler and false otherwise...
+  boolean externalProtocolHandlerExists(in string aProtocolScheme);
+
+  // used to load a url via an external protocol handler (if one exists)
+  // aURL --> the url to load
+  void loadUrl (in nsIURI aURL);  
+};