Issue 6790 - Implement uabinject-defuser snippet

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
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with Adblock Plus.  If not, see <http://www.gnu.org/licenses/>.
  */
 
 /* eslint-env webextensions */
 /* eslint no-console: "off" */
 
 "use strict";
 
-function injectCode(code)
+function injectCode(code, dependencies = [])
 {
+  for (let dependency of dependencies)
+    code += dependency;
+
   let script = document.createElement("script");
 
   script.type = "application/javascript";
   script.async = false;
 
   // Firefox 58 only bypasses site CSPs when assigning to 'src',
   // while Chrome 67 only bypasses site CSPs when using 'textContent'.
   if (browser.runtime.getURL("").startsWith("chrome-extension://"))
   {
     script.textContent = code;
     document.documentElement.appendChild(script);
   }
   else
   {
     let url = URL.createObjectURL(new Blob([code]));
     script.src = url;
     document.documentElement.appendChild(script);
     URL.revokeObjectURL(url);
   }
 
   document.documentElement.removeChild(script);
 }
 
 function stringifyFunctionCall(func, ...params)
 {
-  return `(${func})(${params.map(JSON.stringify).join(",")});`;
+  return `"use strict";(${func})(${params.map(JSON.stringify).join(",")});`;
 }
 
-function makeInjector(injectable)
+function makeInjector(injectable, ...dependencies)
 {
-  return (...args) => injectCode(stringifyFunctionCall(injectable, ...args));
+  return (...args) => injectCode(stringifyFunctionCall(injectable, ...args),
+                                 dependencies);
 }
 
 function log(...args)
 {
   console.log(...args);
 }
 
 exports.log = log;
 
+function trace(...args)
+{
+  log(...args);
+}
+
+exports.trace = makeInjector(trace, log);
+
+// This is an implementation of the uabinject-defuser technique used by uBlock
+// Origin
+// https://github.com/uBlockOrigin/uAssets/blob/c091f861b63cd2254b8e9e4628f6bdcd89d43caa/filters/resources.txt#L640
 function uabinjectDefuser()
 {
   window.trckd = true;
   window.uabpdl = true;
   window.uabInject = true;
   window.uabDetect = true;
 }
 
 exports["uabinject-defuser"] = makeInjector(uabinjectDefuser);