Make things not be broken on FF<29.

common/modules/main.jsm

@@ -111,7 +111,8 @@ var Modules = function Modules(window) {
     const BASES = [BASE, "resource://dactyl-local-content/"];
 
     let proxyCache = {};
-    let proxy = new Proxy(window, {
+    if (config.haveGecko(29))
+        var proxy = new Proxy(window, {
             get: function window_get(target, prop) {
                 // `in`, not `hasOwnProperty`, because we want to return
                 // unbound methods in `Object.prototype`
@@ -129,6 +130,39 @@ var Modules = function Modules(window) {
                 return target[prop] = val;
             }
         });
+    else {
+        // Bug 814892
+        let o = {};
+        // Oh, the brokenness... See bug 793210
+        Object.preventExtensions(o);
+        proxy = new Proxy(o, {
+            get: function window_get(target, prop) {
+                // `in`, not `hasOwnProperty`, because we want to return
+                // unbound methods in `Object.prototype`
+                if (prop in proxyCache)
+                    return proxyCache[prop];
+
+                let p = window[prop];
+                if (callable(p))
+                    return proxyCache[prop] = p.bind(window);
+
+                return p;
+            },
+
+            set: function window_set(target, prop, val) {
+                return window[prop] = val;
+            },
+
+            getOwnPropertyDescriptor: function (target, prop) Object.getOwnPropertyDescriptor(window, prop),
+            getOwnPropertyNames: function (target, prop) Object.getOwnPropertyNames(window),
+            defineProperty: function (target, prop, desc) Object.defineProperty(window, prop, desc),
+            deleteProperty: function (target, prop) { delete window[prop]; },
+            has: function (target, prop) prop in window,
+            hasOwn: function (target, prop) hasOwnProperty(window, prop),
+            enumerate: function (target) (p for (p in window)),
+            iterate: function (target) (p for (p of window))
+        });
+    }
 
     var jsmodules = newContext(proxy, false, "Dactyl `jsmodules`");
     jsmodules.NAME = "jsmodules";