Merge from vscode merge-base (#22780)

* Revert "Revert "Merge from vscode merge-base (#22769)" (#22779)"

This reverts commit 47a1745180.

* Fix notebook download task

* Remove done call from extensions-ci

extensions/markdown-language-features/src/extension.browser.ts

@@ -0,0 +1,42 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the Source EULA. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import * as vscode from 'vscode';
+import { BaseLanguageClient, LanguageClient, LanguageClientOptions } from 'vscode-languageclient/browser';
+import { startClient } from './client';
+import { activateShared } from './extension.shared';
+import { VsCodeOutputLogger } from './logging';
+import { IMdParser, MarkdownItEngine } from './markdownEngine';
+import { getMarkdownExtensionContributions } from './markdownExtensions';
+import { githubSlugifier } from './slugify';
+import { IMdWorkspace, VsCodeMdWorkspace } from './workspace';
+
+export async function activate(context: vscode.ExtensionContext) {
+	const contributions = getMarkdownExtensionContributions(context);
+	context.subscriptions.push(contributions);
+
+	const logger = new VsCodeOutputLogger();
+	context.subscriptions.push(logger);
+
+	const engine = new MarkdownItEngine(contributions, githubSlugifier, logger);
+
+	const workspace = new VsCodeMdWorkspace();
+	context.subscriptions.push(workspace);
+
+	const client = await startServer(context, workspace, engine);
+	context.subscriptions.push({
+		dispose: () => client.stop()
+	});
+	activateShared(context, client, workspace, engine, logger, contributions);
+}
+
+function startServer(context: vscode.ExtensionContext, workspace: IMdWorkspace, parser: IMdParser): Promise<BaseLanguageClient> {
+	const serverMain = vscode.Uri.joinPath(context.extensionUri, 'server/dist/browser/main.js');
+	const worker = new Worker(serverMain.toString());
+
+	return startClient((id: string, name: string, clientOptions: LanguageClientOptions) => {
+		return new LanguageClient(id, name, clientOptions, worker);
+	}, workspace, parser);
+}