src/vs/workbench/browser/parts/activitybar/activitybarPart.ts/ActivitybarPart/installMenubar
class ActivitybarPart:	private installMenubar() {
		if (this.menuBar) {
			return; // prevent menu bar from installing twice #110720
		}

		this.menuBarContainer = document.createElement('div');
		this.menuBarContainer.classList.add('menubar');

		const content = assertIsDefined(this.content);
		content.prepend(this.menuBarContainer);

		// Menubar: install a custom menu bar depending on configuration
		this.menuBar = this._register(this.instantiationService.createInstance(CustomMenubarControl));
		this.menuBar.create(this.menuBarContainer);

		this.registerKeyboardNavigationListeners();
	}