src/vs/platform/files/browser/indexedDBFileSystemProvider.ts/IndexedDBFileSystemProvider/readFile
class IndexedDBFileSystemProvider:	async readFile(resource: URI): Promise<Uint8Array> {
		try {
			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;
		} catch (error) {
			this.reportError('readFile', error);
			throw error;
		}
	}