Mouse: Fixed #3552, reverted r1763: Let mouse events propagate.

ui/ui.core.js

@@ -412,6 +412,9 @@ $.ui.mouse = {
 	},
 
 	_mouseDown: function(event) {
+		// don't let more than one widget handle mouseStart
+		if (event.originalEvent.mouseHandled) { return; }
+
 		// we may have missed mouseup (out of window)
 		(this._mouseStarted && this._mouseUp(event));
 
@@ -455,11 +458,7 @@ $.ui.mouse = {
 		// anymore, so this fix is needed
 		($.browser.safari || event.preventDefault());
 
-		// was changed to return true in rev 1000 because that allows the
-		// event to bubble - however, exactly that causes much pain for
-		// nested widgets, so we call stopPropagation(). Building a work-
-		// around for the above is much easier.
-		event.stopPropagation();
+		event.originalEvent.mouseHandled = true;
 		return true;
 	},