Dispatching KeyboardEvent on Webview fails to work only on Windows.

Dispatching KeyboardEvents on Webview fails to work only on Windows.

Version: 1.51.0-insider (user setup) Commit: 9f7a586124ca121bba906b44eb8356691617957e Date: 2020-10-22T00:49:16.002Z Electron: 9.3.2 Chrome: 83.0.4103.122 Node.js: 12.14.1 V8: 8.3.110.13-electron.0 OS: Windows_NT x64 10.0.18363

Steps to Reproduce:

1. Execute the following sample on Windows.
2. Execute the command Hello World
3. A webview panel is opened, and a new document is not opened.
4. A new document should be opened.

Does this issue occur when all extensions are disabled?: Yes

Related to James-Yu/LaTeX-Workshop/issues/2334 and #108797.

We are dispatching KeyboardEvents on our extension's internal PDF viewer to enable shortcuts on the viewer, which is recommended by @mjbvz. It had been working fine. However, we find that it fails to work only on Windows now. On macOS, it still works fine.

import * as vscode from 'vscode';

const htmlString = `
<script>
// Should work on macOS.
const ev0 = {"altKey":false,"code":"KeyN","ctrlKey":false,"isComposing":false,"key":"n","location":0,"metaKey":true,"repeat":false,"shiftKey":false};
setTimeout(() => window.dispatchEvent(new KeyboardEvent('keydown', ev0)), 2000);

// Should work on windows.
const ev1 = {"altKey":false,"code":"KeyN","ctrlKey":true,"isComposing":false,"key":"n","location":0,"metaKey":false,"repeat":false,"shiftKey":false};
setTimeout(() => window.dispatchEvent(new KeyboardEvent('keydown', ev1)), 3000);
</script>
`

export function activate(context: vscode.ExtensionContext) {
	console.log('Congratulations, your extension "helloworld-sample" is now active!');

	const disposable = vscode.commands.registerCommand('extension.helloWorld', () => {
		const panel = vscode.window.createWebviewPanel(
			'aaa',
			'Cat Coding',
			vscode.ViewColumn.One,
			{
					enableScripts: true,
			}
		)
		panel.webview.html = htmlString
	})
	context.subscriptions.push(disposable);
}