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/ui/modalDialog.js

@@ -4,7 +4,6 @@ const Clutter = imports.gi.Clutter;
 const Gdk = imports.gi.Gdk;
 const Gio = imports.gi.Gio;
 const GLib = imports.gi.GLib;
-const Lang = imports.lang;
 const Meta = imports.gi.Meta;
 const Pango = imports.gi.Pango;
 const St = imports.gi.St;
@@ -31,10 +30,8 @@ var State = {
     FADED_OUT: 4
 };
 
-var ModalDialog = new Lang.Class({
-    Name: 'ModalDialog',
-
-    _init(params) {
+var ModalDialog = class {
+    constructor(params) {
         params = Params.parse(params, { shellReactive: false,
                                         styleClass: null,
                                         actionMode: Shell.ActionMode.SYSTEM_MODAL,
@@ -87,30 +84,30 @@ var ModalDialog = new Lang.Class({
         this._initialKeyFocus = null;
         this._initialKeyFocusDestroyId = 0;
         this._savedKeyFocus = null;
-    },
+    }
 
     destroy() {
         this._group.destroy();
-    },
+    }
 
     clearButtons() {
         this.dialogLayout.clearButtons();
-    },
+    }
 
     setButtons(buttons) {
         this.clearButtons();
 
         for (let buttonInfo of buttons)
             this.addButton(buttonInfo);
-    },
+    }
 
     addButton(buttonInfo) {
         return this.dialogLayout.addButton(buttonInfo);
-    },
+    }
 
     _onGroupDestroy() {
         this.emit('destroy');
-    },
+    }
 
     _fadeOpen(onPrimary) {
         if (onPrimary)
@@ -134,7 +131,7 @@ var ModalDialog = new Lang.Class({
                                this.emit('opened');
                            }
                          });
-    },
+    }
 
     setInitialKeyFocus(actor) {
         if (this._initialKeyFocusDestroyId)
@@ -146,7 +143,7 @@ var ModalDialog = new Lang.Class({
             this._initialKeyFocus = null;
             this._initialKeyFocusDestroyId = 0;
         });
-    },
+    }
 
     open(timestamp, onPrimary) {
         if (this.state == State.OPENED || this.state == State.OPENING)
@@ -157,7 +154,7 @@ var ModalDialog = new Lang.Class({
 
         this._fadeOpen(onPrimary);
         return true;
-    },
+    }
 
     _closeComplete() {
         this.state = State.CLOSED;
@@ -166,7 +163,7 @@ var ModalDialog = new Lang.Class({
 
         if (this._destroyOnClose)
             this.destroy();
-    },
+    }
 
     close(timestamp) {
         if (this.state == State.CLOSED || this.state == State.CLOSING)
@@ -185,7 +182,7 @@ var ModalDialog = new Lang.Class({
                              })
         else
             this._closeComplete();
-    },
+    }
 
     // Drop modal status without closing the dialog; this makes the
     // dialog insensitive as well, so it needs to be followed shortly
@@ -205,7 +202,7 @@ var ModalDialog = new Lang.Class({
 
         if (!this._shellReactive)
             this._eventBlocker.raise_top();
-    },
+    }
 
     pushModal(timestamp) {
         if (this._hasModal)
@@ -229,7 +226,7 @@ var ModalDialog = new Lang.Class({
         if (!this._shellReactive)
             this._eventBlocker.lower_bottom();
         return true;
-    },
+    }
 
     // This method is like close, but fades the dialog out much slower,
     // and leaves the lightbox in place. Once in the faded out state,
@@ -259,5 +256,5 @@ var ModalDialog = new Lang.Class({
                            }
                          });
     }
-});
+};
 Signals.addSignalMethods(ModalDialog.prototype);