src/vs/workbench/api/common/extHostDocumentContentProviders.ts/ExtHostDocumentContentProvider/$provideTextDocumentContent
class ExtHostDocumentContentProvider:	$provideTextDocumentContent(handle: number, uri: UriComponents): Promise<string | null | undefined> {
		const provider = this._documentContentProviders.get(handle);
		if (!provider) {
			return Promise.reject(new Error(`unsupported uri-scheme: ${uri.scheme}`));
		}
		return Promise.resolve(provider.provideTextDocumentContent(URI.revive(uri), CancellationToken.None));
	}