cleanup: Port non-GObject classes to JS6 classes

ES6 finally adds standard class syntax to the language, so we can
replace our custom Lang.Class framework with the new syntax. Any
classes that inherit from GObject will need special treatment,
so limit the port to regular javascript classes for now.

https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/361

js/gdm/batch.js

@@ -44,45 +44,39 @@
  * replaced by something else.
  */
 
-const Lang = imports.lang;
 const Signals = imports.signals;
 
-var Task = new Lang.Class({
-    Name: 'Task',
-
-    _init(scope, handler) {
+var Task = class {
+    constructor(scope, handler) {
         if (scope)
             this.scope = scope;
         else
             this.scope = this;
 
         this.handler = handler;
-    },
+    }
 
     run() {
         if (this.handler)
             return this.handler.call(this.scope);
 
         return null;
-    },
-});
+    }
+};
 Signals.addSignalMethods(Task.prototype);
 
-var Hold = new Lang.Class({
-    Name: 'Hold',
-    Extends: Task,
-
-    _init() {
-        this.parent(this, () => this);
+var Hold = class extends Task {
+    constructor() {
+        super(null, () => this);
 
         this._acquisitions = 1;
-    },
+    }
 
     acquire() {
         if (this._acquisitions <= 0)
             throw new Error("Cannot acquire hold after it's been released");
         this._acquisitions++;
-    },
+    }
 
     acquireUntilAfter(hold) {
         if (!hold.isAcquired())
@@ -93,27 +87,24 @@ var Hold = new Lang.Class({
             hold.disconnect(signalId);
             this.release();
         });
-    },
+    }
 
     release() {
         this._acquisitions--;
 
         if (this._acquisitions == 0)
             this.emit('release');
-    },
+    }
 
     isAcquired() {
         return this._acquisitions > 0;
     }
-});
+};
 Signals.addSignalMethods(Hold.prototype);
 
-var Batch = new Lang.Class({
-    Name: 'Batch',
-    Extends: Task,
-
-    _init(scope, tasks) {
-        this.parent();
+var Batch = class extends Task {
+    constructor(scope, tasks) {
+        super();
 
         this.tasks = [];
 
@@ -130,11 +121,11 @@ var Batch = new Lang.Class({
 
             this.tasks.push(task);
         }
-    },
+    }
 
     process() {
         throw new Error('Not implemented');
-    },
+    }
 
     runTask() {
         if (!(this._currentTaskIndex in this.tasks)) {
@@ -142,11 +133,11 @@ var Batch = new Lang.Class({
         }
 
         return this.tasks[this._currentTaskIndex].run();
-    },
+    }
 
     _finish() {
         this.hold.release();
-    },
+    }
 
     nextTask() {
         this._currentTaskIndex++;
@@ -159,7 +150,7 @@ var Batch = new Lang.Class({
         }
 
         this.process();
-    },
+    }
 
     _start() {
         // acquire a hold to get released when the entire
@@ -167,7 +158,7 @@ var Batch = new Lang.Class({
         this.hold = new Hold();
         this._currentTaskIndex = 0;
         this.process();
-    },
+    }
 
     run() {
         this._start();
@@ -175,18 +166,15 @@ var Batch = new Lang.Class({
         // hold may be destroyed at this point
         // if we're already done running
         return this.hold;
-    },
+    }
 
     cancel() {
         this.tasks = this.tasks.splice(0, this._currentTaskIndex + 1);
     }
-});
+};
 Signals.addSignalMethods(Batch.prototype);
 
-var ConcurrentBatch = new Lang.Class({
-    Name: 'ConcurrentBatch',
-    Extends: Batch,
-
+var ConcurrentBatch = class extends Batch {
     process() {
        let hold = this.runTask();
 
@@ -199,13 +187,10 @@ var ConcurrentBatch = new Lang.Class({
        // concurrently.
        this.nextTask();
     }
-});
+};
 Signals.addSignalMethods(ConcurrentBatch.prototype);
 
-var ConsecutiveBatch = new Lang.Class({
-    Name: 'ConsecutiveBatch',
-    Extends: Batch,
-
+var ConsecutiveBatch = class extends Batch {
     process() {
        let hold = this.runTask();
 
@@ -222,5 +207,5 @@ var ConsecutiveBatch = new Lang.Class({
            this.nextTask();
        }
     }
-});
+};
 Signals.addSignalMethods(ConsecutiveBatch.prototype);