src/vs/base/common/map.ts/LinkedMap/trimOld
class LinkedMap:	protected trimOld(newSize: number) {
		if (newSize >= this.size) {
			return;
		}
		if (newSize === 0) {
			this.clear();
			return;
		}
		let current = this._head;
		let currentSize = this.size;
		while (current && currentSize > newSize) {
			this._map.delete(current.key);
			current = current.next;
			currentSize--;
		}
		this._head = current;
		this._size = currentSize;
		if (current) {
			current.previous = undefined;
		}
		this._state++;
	}