src/vs/platform/files/browser/indexedDBFileSystemProvider.ts/IndexedDBFileSystemProvider/readFile
class IndexedDBFileSystemProvider:	async readFile(resource: URI): Promise<Uint8Array> {
		const result = await this.indexedDB.runInTransaction(this.store, 'readonly', objectStore => objectStore.get(resource.path));
		if (result === undefined) {
			throw ERR_FILE_NOT_FOUND;
		}
		const buffer = result instanceof Uint8Array ? result : isString(result) ? VSBuffer.fromString(result).buffer : undefined;
		if (buffer === undefined) {
			throw ERR_UNKNOWN_INTERNAL(`IndexedDB entry at "${resource.path}" in unexpected format`);
		}

		// update cache
		const fileTree = await this.getFiletree();
		fileTree.add(resource.path, { type: 'file', size: buffer.byteLength });

		return buffer;
	}