--- a/.eslintignore
+++ b/.eslintignore
@@ -3,17 +3,16 @@
 
 # Exclude expected objdirs.
 obj*/**
 
 # We ignore all these directories by default, until we get them enabled.
 # If you are enabling a directory, please add directory specific exclusions
 # below.
 chrome/**
-config/**
 docshell/**
 editor/**
 embedding/**
 extensions/cookie/**
 extensions/spellcheck/**
 extensions/universalchardet/**
 gfx/**
 image/**
@@ -31,16 +30,17 @@ tools/update-packaging/**
 uriloader/**
 view/**
 widget/**
 xpcom/**
 
 # We currently have no js files in these directories, so we ignore them by
 # default to aid ESLint's performance.
 build/**
+config/**
 db/**
 gradle/**
 hal/**
 mfbt/**
 mozglue/**
 nsprpub/**
 other-licenses/**
 probes/**

deleted file mode 100644
--- a/config/string-format.js
+++ /dev/null
@@ -1,65 +0,0 @@
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-String.prototype.format = function string_format() {
-  // there are two modes of operation... unnamed indices are read in order;
-  // named indices using %(name)s. The two styles cannot be mixed.
-  // Unnamed indices can be passed as either a single argument to this function,
-  // multiple arguments to this function, or as a single array argument
-  let curindex = 0;
-  let d;
-
-  if (arguments.length > 1) {
-    d = arguments;
-  }
-  else
-    d = arguments[0];
-
-  function r(s, key, type) {
-    if (type == '%')
-      return '%';
-    
-    let v;
-    if (key == "") {
-      if (curindex == -1)
-        throw Error("Cannot mix named and positional indices in string formatting.");
-
-      if (curindex == 0 && (!(d instanceof Object) || !(0 in d))) {
-        v = d;
-      }
-      else if (!(curindex in d))
-        throw Error("Insufficient number of items in format, requesting item %i".format(curindex));
-      else {
-        v = d[curindex];
-      }
-
-      ++curindex;
-    }
-    else {
-      key = key.slice(1, -1);
-      if (curindex > 0)
-        throw Error("Cannot mix named and positional indices in string formatting.");
-      curindex = -1;
-
-      if (!(key in d))
-        throw Error("Key '%s' not present during string substitution.".format(key));
-      v = d[key];
-    }
-    switch (type) {
-    case "s":
-      if (v === undefined)
-        return "<undefined>";
-      return v.toString();
-    case "r":
-      return uneval(v);
-    case "i":
-      return parseInt(v);
-    case "f":
-      return Number(v);
-    default:
-      throw Error("Unexpected format character '%s'.".format(type));
-    }
-  }
-  return this.replace(/%(\([^)]+\))?(.)/g, r);
-};