Replace expression closures (function expressions - named and dynamic this).

Expression closures are to be axed. See https://bugzil.la/1083458.

Leaving deprecated() and literal() calls and method shorthand syntax
conversions until after the ESR overlap.

common/content/mappings.js

@@ -45,10 +45,12 @@ var Map = Class("Map", {
         }
     },
 
-    name: Class.Memoize(function () this.names[0]),
+    name: Class.Memoize(function () { return this.names[0]; }),
 
     /** @property {[string]} All of this mapping's names (key sequences). */
-    names: Class.Memoize(function () this._keys.map(k => DOM.Event.canonicalKeys(k))),
+    names: Class.Memoize(function () {
+        return this._keys.map(k => DOM.Event.canonicalKeys(k));
+    }),
 
     get toStringParams() {
         return [this.modes.map(m => m.name),