Bug 1115773 - Allow L10n's loadJSON to be sync. r=gandalf

lib/client/l20n/platform/io.js

@@ -5,46 +5,33 @@
 /* exported io */
 
 var io = {
-  load: function load(url, callback, sync) {
+
+  _load: function(type, url, callback, sync) {
     var xhr = new XMLHttpRequest();
+    var needParse;
 
     if (xhr.overrideMimeType) {
-      xhr.overrideMimeType('text/plain');
+      xhr.overrideMimeType(type);
     }
 
     xhr.open('GET', url, !sync);
 
-    xhr.addEventListener('load', function io_load(e) {
-      if (e.target.status === 200 || e.target.status === 0) {
-        callback(null, e.target.responseText);
+    if (type === 'application/json') {
+      //  Gecko 11.0+ forbids the use of the responseType attribute when
+      //  performing sync requests (NS_ERROR_DOM_INVALID_ACCESS_ERR).
+      //  We'll need to JSON.parse manually.
+      if (sync) {
+        needParse = true;
       } else {
-        callback(new L10nError('Not found: ' + url));
+        xhr.responseType = 'json';
       }
-    });
-    xhr.addEventListener('error', callback);
-    xhr.addEventListener('timeout', callback);
-
-    // the app: protocol throws on 404, see https://bugzil.la/827243
-    try {
-      xhr.send(null);
-    } catch (e) {
-      callback(new L10nError('Not found: ' + url));
-    }
-  },
-
-  loadJSON: function loadJSON(url, callback) {
-    var xhr = new XMLHttpRequest();
-
-    if (xhr.overrideMimeType) {
-      xhr.overrideMimeType('application/json');
     }
 
-    xhr.open('GET', url);
-
-    xhr.responseType = 'json';
-    xhr.addEventListener('load', function io_loadjson(e) {
+    xhr.addEventListener('load', function io_onload(e) {
       if (e.target.status === 200 || e.target.status === 0) {
-        callback(null, e.target.response);
+        // Sinon.JS's FakeXHR doesn't have the response property
+        var res = e.target.response || e.target.responseText;
+        callback(null, needParse ? JSON.parse(res) : res);
       } else {
         callback(new L10nError('Not found: ' + url));
       }
@@ -58,5 +45,14 @@ var io = {
     } catch (e) {
       callback(new L10nError('Not found: ' + url));
     }
+  },
+
+  load: function(url, callback, sync) {
+    return io._load('text/plain', url, callback, sync);
+  },
+
+  loadJSON: function(url, callback, sync) {
+    return io._load('application/json', url, callback, sync);
   }
+
 };