Issue 6538, 6781 - Add code injection wrapper to snippets library

lib/content/snippets.js

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-present eyeo GmbH
  *
  * Adblock Plus is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 3 as
  * published by the Free Software Foundation.
  *
  * Adblock Plus is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 40 matching lines @@
     let url = URL.createObjectURL(new Blob([code]));
     script.src = url;
     document.documentElement.appendChild(script);
     URL.revokeObjectURL(url);
   }
 
   document.documentElement.removeChild(script);
 }
 
 /**
- * Safely converts a function and an optional list of arguments into a string
- * of code containing a function call. The function is converted to its string
+ * Converts a function and an optional list of arguments into a string of code
+ * containing a function call. The function is converted to its string
  * representation using the <code>Function.prototype.toString</code> method.
  * Each argument is stringified using <code>JSON.stringify</code>. The
  * generated code begins with the <code>"use strict"</code> directive.
  *
  * @param {function} func The function to convert.
  * @param {...*} [params] The arguments to convert.
  *
  * @returns {string} The generated code containing the function call.
  */
 function stringifyFunctionCall(func, ...params)
 {
-  // Call the original Function.prototype.toString to avoid any arbitrary code
-  // execution.
-  func = Function.prototype.toString.call(func);
-
   // Call JSON.stringify on the arguments to avoid any arbitrary code
   // execution.
-  params = params.map(JSON.stringify);
-
-  return `"use strict";(${func})(${params.join(",")});`;
+  return `"use strict";(${func})(${params.map(JSON.stringify).join(",")});`;
 }
 
 /**
  * Wraps a function and its dependencies into an injector. The injector, when
  * called with zero or more arguments, generates code that calls the function,
  * with the given arguments, if any, and injects the code, along with any
  * dependencies, into the document using a temporary <code>script</code>
  * element.
  *
  * @param {function} injectable The function to wrap into an injector.
@@ skipping 31 matching lines @@
  * @param {...*} [args] The arguments to log.
  */
 function trace(...args)
 {
   // We could simply use console.log here, but the goal is to demonstrate the
   // usage of snippet dependencies.
   log(...args);
 }
 
 exports.trace = makeInjector(trace, log);