src/vs/workbench/api/common/extHostProfileContentHandler.ts/ExtHostProfileContentHandlers/registrProfileContentHandler
class ExtHostProfileContentHandlers:	registrProfileContentHandler(
		extension: IExtensionDescription,
		id: string,
		handler: vscode.ProfileContentHandler,
	): vscode.Disposable {
		checkProposedApiEnabled(extension, 'profileContentHandlers');
		if (this.handlers.has(id)) {
			throw new Error(`Handler with id '${id}' already registered`);
		}

		this.handlers.set(id, handler);
		this.proxy.$registerProfileContentHandler(id, handler.name, extension.identifier.value);

		return toDisposable(() => {
			this.handlers.delete(id);
			this.proxy.$unregisterProfileContentHandler(id);
		});
	}