Send Stickers: Plug the sticker picker widget with the room datasource to send a sticker

#1860

Riot/ViewController/Widgets/WidgetViewController.h

@@ -17,6 +17,7 @@
 #import "WebViewViewController.h"
 
 #import "WidgetManager.h"
+#import "MatrixKit/MatrixKit.h"
 
 /**
  `WidgetViewController` displays widget within a webview.
@@ -26,6 +27,12 @@
  */
 @interface WidgetViewController : WebViewViewController
 
+/**
+ The room data source.
+ Required if the widget needs to post messages.
+ */
+@property (nonatomic) MXKRoomDataSource *roomDataSource;
+
 /**
  Init 'WidgetViewController' instance with a widget.