src/vs/workbench/browser/parts/editor/editorPane.ts/EditorMemento/doLoad
class EditorMemento:	private doLoad(): LRUCache<string, MapGroupToMemento<T>> {
		if (!this.cache) {
			this.cache = new LRUCache<string, MapGroupToMemento<T>>(this.limit);

			// Restore from serialized map state
			const rawEditorMemento = this.memento[this.key];
			if (Array.isArray(rawEditorMemento)) {
				this.cache.fromJSON(rawEditorMemento);
			}
		}

		return this.cache;
	}