src/vs/workbench/browser/parts/views/viewPaneContainer.ts/ViewPaneContainer/updateViewHeaders
class ViewPaneContainer:	private updateViewHeaders(): void {
		if (this.isViewMergedWithContainer()) {
			if (this.paneItems[0].pane.isExpanded()) {
				this.lastMergedCollapsedPane = undefined;
			} else {
				this.lastMergedCollapsedPane = this.paneItems[0].pane;
				this.paneItems[0].pane.setExpanded(true);
			}
			this.paneItems[0].pane.headerVisible = false;
		} else {
			this.paneItems.forEach(i => {
				i.pane.headerVisible = true;
				if (i.pane === this.lastMergedCollapsedPane) {
					i.pane.setExpanded(false);
				}
			});
			this.lastMergedCollapsedPane = undefined;
		}
	}