perf: update scrollable toolbars in task #15091

Fixes #15091

- very frequent task
- happens on resize of window, scroll of document, status of commands
- example is scrolling between Writer pages when we need to update
  page number in statusbar - causing it to happen synchronously and
  reducing frame rate on that fragments

Signed-off-by: Szymon Kłos <szymon.klos@collabora.com>
Change-Id: I46e8426c7417bb4c33c45e1967f60114900ef835

Author: eszkadev

browser/src/control/jsdialog/Util.ScrollableBar.ts

@@ -52,7 +52,7 @@ function setupResizeHandler(container: Element, scrollable: Element) {
 	var isRTL: boolean = document.documentElement.dir === 'rtl';
 	var timer: any; // for shift + mouse wheel up/down
 
-	const handler = function () {
+	const handlerImpl = () => {
 		const rootContainer = scrollable.querySelector('div');
 		if (!rootContainer) return;
 
@@ -77,7 +77,11 @@ function setupResizeHandler(container: Element, scrollable: Element) {
 			showArrow(left, false);
 			showArrow(right, false);
 		}
-	}.bind(this);
+	};
+
+	const handler = () => {
+		app.layoutingService.appendLayoutingTask(handlerImpl);
+	};
 
 	// handler for toolbar and statusbar
 	// runs if shift + mouse wheel up/down are used