Issue 4795 - Use modern JavaScript syntax

lib/io.js

Index: lib/io.js
diff --git a/lib/io.js b/lib/io.js
index 6a07389c6f2eafec04176b87cf46de1cacbd17c6..d7f12d00e55fb04ef4c50d4b6f639cd20cf5d2ae 100644
--- a/lib/io.js
+++ b/lib/io.js
@@ -26,7 +26,7 @@ function loadFile(file, successCallback, errorCallback)
 {
   let key = fileToKey(file);
 
-  ext.storage.get([key], function(items)
+  ext.storage.get([key], items =>
   {
     let entry = items[key];
 
@@ -51,12 +51,9 @@ function saveFile(file, data, callback)
 
 exports.IO =
 {
-  resolveFilePath: function(path)
-  {
-    return new FakeFile(path);
-  },
+  resolveFilePath: path => new FakeFile(path),
 
-  readFromFile: function(file, listener, callback)
+  readFromFile: (file, listener, callback) =>
   {
     function onLoaded(entry)
     {
@@ -70,12 +67,12 @@ exports.IO =
     loadFile(file, onLoaded, callback);
   },
 
-  writeToFile: function(file, data, callback)
+  writeToFile: (file, data, callback) =>
   {
     saveFile(file, data, callback);
   },
 
-  copyFile: function(fromFile, toFile, callback)
+  copyFile: (fromFile, toFile, callback) =>
   {
     function onLoaded(entry)
     {
@@ -85,11 +82,11 @@ exports.IO =
     loadFile(fromFile, onLoaded, callback);
   },
 
-  renameFile: function(fromFile, newName, callback)
+  renameFile: (fromFile, newName, callback) =>
   {
     function onLoaded(entry)
     {
-      ext.storage.remove(fileToKey(fromFile), function()
+      ext.storage.remove(fileToKey(fromFile), () =>
       {
         ext.storage.set(keyPrefix + newName, entry, callback);
       });
@@ -98,12 +95,12 @@ exports.IO =
     loadFile(fromFile, onLoaded, callback);
   },
 
-  removeFile: function(file, callback)
+  removeFile: (file, callback) =>
   {
     ext.storage.remove(fileToKey(file), callback);
   },
 
-  statFile: function(file, callback)
+  statFile: (file, callback) =>
   {
     function onLoaded(entry)
     {