view-selector: Remove show/hide functions

As Main.overview is now usable from the view selector's constructor,
move the setup of signal connections there and remove the show/hide
methods which were used as workaround.

https://bugzilla.gnome.org/show_bug.cgi?id=642196

js/ui/overview.js

@@ -535,7 +535,6 @@ Overview.prototype = {
         this._group.show();
         this._background.show();
 
-        this.viewSelector.show();
         this._workspacesDisplay.show();
 
         this.workspaces = this._workspacesDisplay.workspacesView;
@@ -749,7 +748,6 @@ Overview.prototype = {
         this.workspaces = null;
 
         this._workspacesDisplay.hide();
-        this.viewSelector.hide();
 
         this._desktopFade.hide();
         this._background.hide();