Issue 6887 - add Chrome to "npm test"

package.json

 {
   "name": "adblockpluschrome",
   "repository": "https://hg.adblockplus.org/adblockpluschrome",
   "license": "GPL-3.0",
   "dependencies": {},
   "devDependencies": {
     "//": [
       "'dmg', 'extract-zip' and 'ncp' are needed by `download_*.js` modules",
       "in adblockpluscore/test/.",
-      "The chromedriver version was pinned to that exact version, due tu in-",

[Sebastian Noack, 2018/08/27 19:56:15]

Typo: It's "due to incompatibilities".

[tlucas, 2018/08/28 08:18:13]

That's exactly what's written here?... Or do you mean the line breaking?

[Sebastian Noack, 2018/08/28 14:44:57]

It's not. What's written here is "due tu in-compatibilities"
                                       ^   ^

[tlucas, 2018/08/29 09:16:53]

Done.

-      "compatibilities with the configured chromium version and newer drivers."
+      "The chromedriver version was pinned to that exact version, due to",
+      "incompatibilities with the configured chromium version and newer",
+      "drivers."
     ],
     "chromedriver": "2.36.0",
     "dmg": "^0.1.0",
     "eslint": "^5.1.0",
     "eslint-config-eyeo": "^2.1.0",
     "extract-zip": "^1.6.5",
     "geckodriver": "^1.9.0",
     "ncp": "^2.0.0",
     "mocha": "^5.2.0",
     "selenium-webdriver": "^3.6.0"
   },
   "scripts": {
+    "pretest": "python ensure_dependencies.py",
     "lint": "eslint *.js lib/ qunit/ ext/ test/",
     "test": "mocha",
     "posttest": "npm run lint"
   }
 }