src/vs/workbench/browser/parts/compositeBar.ts/CompositeBar/computeSizes
class CompositeBar:	private computeSizes(items: ICompositeBarModelItem[]): void {
		const size = this.options.compositeSize;
		if (size) {
			items.forEach(composite => this.compositeSizeInBar.set(composite.id, size));
		} else {
			const compositeSwitcherBar = this.compositeSwitcherBar;
			if (compositeSwitcherBar && this.dimension && this.dimension.height !== 0 && this.dimension.width !== 0) {

				// Compute sizes only if visible. Otherwise the size measurment would be computed wrongly.
				const currentItemsLength = compositeSwitcherBar.viewItems.length;
				compositeSwitcherBar.push(items.map(composite => composite.activityAction));
				items.map((composite, index) => this.compositeSizeInBar.set(composite.id, this.options.orientation === ActionsOrientation.VERTICAL
					? compositeSwitcherBar.getHeight(currentItemsLength + index)
					: compositeSwitcherBar.getWidth(currentItemsLength + index)
				));
				items.forEach(() => compositeSwitcherBar.pull(compositeSwitcherBar.viewItems.length - 1));
			}
		}
	}