Draggable: Apply ui-draggable-dragging class prior to calculating dim…

…ensions. Fixes #8349 - Draggable: Incorrect dimensions used if .ui-draggable-dragging changes dimensions

(cherry picked from commit a0c18ea)

ui/jquery.ui.draggable.js

@@ -103,6 +103,8 @@ $.widget("ui.draggable", $.ui.mouse, {
 		//Create and append the visible helper
 		this.helper = this._createHelper(event);
 
+		this.helper.addClass("ui-draggable-dragging");
+
 		//Cache the helper size
 		this._cacheHelperProportions();
 
@@ -163,7 +165,7 @@ $.widget("ui.draggable", $.ui.mouse, {
 		if ($.ui.ddmanager && !o.dropBehaviour)
 			$.ui.ddmanager.prepareOffsets(this, event);
 
-		this.helper.addClass("ui-draggable-dragging");
+
 		this._mouseDrag(event, true); //Execute the drag once - this causes the helper not to be visible before getting its correct position
 
 		//If the ddmanager is used for droppables, inform the manager that dragging has started (see #5003)