src/vs/workbench/browser/web.main.ts/BrowserMain/resolveWorkspaceInitializationPayload
class BrowserMain:	private resolveWorkspaceInitializationPayload(): IAnyWorkspaceIdentifier {
		let workspace: IWorkspace | undefined = undefined;
		if (this.configuration.workspaceProvider) {
			workspace = this.configuration.workspaceProvider.workspace;
		}

		// Multi-root workspace
		if (workspace && isWorkspaceToOpen(workspace)) {
			return getWorkspaceIdentifier(workspace.workspaceUri);
		}

		// Single-folder workspace
		if (workspace && isFolderToOpen(workspace)) {
			return getSingleFolderWorkspaceIdentifier(workspace.folderUri);
		}

		return { id: 'empty-window' };
	}