Firefox: new method for request handling

Now both nsIContentPolicy and on-http-* observers are used for net request
monitoring.

Reasons:
 - In many cases, nsIContentPolicy.shouldLoad is invoked twice for the same
   resource, because of the speculative parsing.
 - nsIContentPolicy.shouldLoad don't have information about the channel,
   so it can't redirect the request, nor change its headers, however
   on-http-opening-request can.

Also, local mirroring and inline-script blocking has been implemented.

platform/firefox/frameScript.js

@@ -23,20 +23,18 @@
 
 /******************************************************************************/
 
+// https://bugzil.la/673569
+
 (function(frameScriptContext) {
 
 'use strict';
 
 /******************************************************************************/
 
-let appName;
+let appName = Components.stack.filename.match(/:\/\/([^\/]+)/)[1];
 let listeners = {};
 
-try { throw new Error; } catch (ex) {
-    appName = ex.fileName.match(/:\/\/([^\/]+)/)[1];
-}
-
-Components.utils['import']('chrome://' + appName + '/content/frameModule.js', {});
+Components.utils['import'](Components.stack.filename.replace('Script', 'Module'), {});
 
 /******************************************************************************/