Add a wrapper to mixpanel so that we can selectively enable metrics collection

(imported from commit 1d72f2e98c4c756a8a988d08731282e4195b8e1a)

humbug/settings.py

@@ -308,6 +308,7 @@ PIPELINE_JS = {
             'js/templates.js',
             'js/settings.js',
             'js/tab_bar.js',
+            'js/metrics.js'
         ],
         'output_filename': 'min/app.js'
     },

tools/jslint/check-all.js

@@ -3,7 +3,7 @@
 // Global variables, categorized by place of definition.
 var globals =
     // Third-party libraries
-      ' $ jQuery Spinner Handlebars XDate zxcvbn Intl'
+      ' $ jQuery Spinner Handlebars XDate zxcvbn Intl mixpanel'
 
     // index.html
     + ' page_params'

zephyr/static/js/metrics.js

@@ -0,0 +1,31 @@
+var metrics = (function () {
+
+var exports = {people: {}};
+
+function enable_metrics() {
+    return page_params.domain === "humbughq.com";
+}
+
+var methods = ["disable", "track", "track_pageview", "track_links", "track_forms",
+               "register", "register_once", "alias", "unregister", "identify",
+               "name_tag", "set_config"];
+var people_methods = ["set", "set_once", "increment", "append", "track_charge",
+                      "clear_charges", "delete_user"];
+
+function wrap_method(name, source_container, target_container) {
+    source_container[name] = function metrics_wrapper () {
+        if (enable_metrics()) {
+            return target_container[name].apply(target_container, arguments);
+        }
+    };
+}
+
+$.each(methods, function (idx, method) {
+    wrap_method(method, exports, mixpanel);
+});
+
+$.each(people_methods, function (idx, method) {
+    wrap_method(method, exports.people, mixpanel.people);
+});
+return exports;
+}());