Bug 874963 - Work - popups don't move when scrolling. r=fryn

browser/metro/base/content/helperui/MenuUI.js

@@ -352,6 +352,7 @@ MenuPopup.prototype = {
     window.addEventListener("keypress", this, true);
     window.addEventListener("mousedown", this, true);
     Elements.stack.addEventListener("PopupChanged", this, false);
+    Elements.browsers.addEventListener("PanBegin", this, false);
 
     this._panel.hidden = false;
     this._position(aPositionOptions || {});
@@ -382,6 +383,7 @@ MenuPopup.prototype = {
     window.removeEventListener("keypress", this, true);
     window.removeEventListener("mousedown", this, true);
     Elements.stack.removeEventListener("PopupChanged", this, false);
+    Elements.browsers.removeEventListener("PanBegin", this, false);
 
     let self = this;
     this._panel.addEventListener("transitionend", function () {
@@ -497,6 +499,9 @@ MenuPopup.prototype = {
           this.hide();
         }
         break;
+      case "PanBegin":
+        this.hide();
+        break;
     }
   }
 };