Made the visibility of Buttom bar updated at the end of drag selection.

chrome/browser/resources/file_manager/js/drag_selector.js

Index: chrome/browser/resources/file_manager/js/drag_selector.js
diff --git a/chrome/browser/resources/file_manager/js/drag_selector.js b/chrome/browser/resources/file_manager/js/drag_selector.js
index 93bf1c5953e7bf63bd331b2bb39eea62ed015c6b..9766c6ebddf7d5386020efd704413f98e21df717 100644
--- a/chrome/browser/resources/file_manager/js/drag_selector.js
+++ b/chrome/browser/resources/file_manager/js/drag_selector.js
@@ -238,7 +238,10 @@ DragSelector.prototype.onMouseUp_ = function(event) {
       'mousemove', this.onMouseMoveBound_, true);
   this.target_.ownerDocument.removeEventListener(
       'mouseup', this.onMouseUpBound_, true);
+  cr.dispatchSimpleEvent(this.target_, 'dragselectionend');
   this.target_.cachedBounds = null;
-  event.stopPropagation();
   this.target_ = null;
+  // The target may select an item by reacting to the mouseup event.
+  // This surpress to the selecting behavior.
+  event.stopPropagation();
 };