webview: ignore Ctrl+W and Ctrl+N in webview for PWA (#164981)

This fixes closing Release Notes / Markdown Preview with Ctrl+W closing whole PWA.

PWAs can intercept the Ctrl+W/Ctrl+N keystrokes, and VSCode does this for editor tabs. However, webviews do not intercept these keystrokes.

If a webview such as Release Notes or Markdown Preview has focus:

- when the user presses Ctrl+N, another instance of the PWA is opened in a new window.
- when the user presses Ctrl+W, the whole PWA window closes.

See https://github.com/microsoft/vscode/issues/150735 for details.

This fixes the issue by ignoring Ctrl+W and Ctrl+N in webviews.

Tested on macOS 12.6 / Chrome Dev 109.0.5384.0:

- patch environmentService.ts webviewExternalEndpoint to use
  http://localhost:8080/static/sources/out/vs/workbench/contrib/webview/browser/pre/
- followed the contributing instruction to run code-web
- in Chrome, More Tools -> Create Shortcut -> Open as window
- closed and re-opened Code OSS PWA window
- opened chrome://inspect and inspected the Code OSS window
- added an uncaught exception handler
- opened file.md and chose "Open preview"
- when it hit
  `Expected '${parentOriginHash}' as hostname or subdomain!`
  manually ran `start(parentOrigin)` in console and continued
- the markdown preview now displayed
- pressed Command+W

Before: the whole window closes
After: only the Markdown preview tab closes

src/vs/workbench/contrib/webview/browser/pre/index-no-csp.html

@@ -589,6 +589,10 @@
 				} else {
 					return; // let the browser handle this
 				}
+			} else if (!onElectron && (isCloseTab(e) || isNewWindow(e))) {
+				// Prevent Ctrl+W closing window / Ctrl+N opening new window in PWA.
+				// (No effect in a regular browser tab.)
+				e.preventDefault();
 			}
 
 			hostMessaging.postMessage('did-keydown', {
@@ -655,6 +659,24 @@
 			return hasMeta && e.key.toLowerCase() === 'f';
 		}
 
+		/**
+		 * @param {KeyboardEvent} e
+		 * @return {boolean}
+		 */
+		function isCloseTab(e) {
+			const hasMeta = e.ctrlKey || e.metaKey;
+			return hasMeta && e.key.toLowerCase() === 'w';
+		}
+
+		/**
+		 * @param {KeyboardEvent} e
+		 * @return {boolean}
+		 */
+		function isNewWindow(e) {
+			const hasMeta = e.ctrlKey || e.metaKey;
+			return hasMeta && e.key.toLowerCase() === 'n';
+		}
+
 		let isHandlingScroll = false;
 
 		/**

src/vs/workbench/contrib/webview/browser/pre/index.html

@@ -5,7 +5,7 @@
 	<meta charset="UTF-8">
 
 	<meta http-equiv="Content-Security-Policy"
-		content="default-src 'none'; script-src 'sha256-lC8sxUeeYqUtmkCpPt/OX/HQdE0JbHG1Z3dzrilsRU0=' 'self'; frame-src 'self'; style-src 'unsafe-inline';">
+		content="default-src 'none'; script-src 'sha256-DmsqQtB7vkf/ey+8HeQmSYaMMdiE0Au1IXEkLBE+OtY=' 'self'; frame-src 'self'; style-src 'unsafe-inline';">
 
 	<!-- Disable pinch zooming -->
 	<meta name="viewport"
@@ -590,6 +590,10 @@
 				} else {
 					return; // let the browser handle this
 				}
+			} else if (!onElectron && (isCloseTab(e) || isNewWindow(e))) {
+				// Prevent Ctrl+W closing window / Ctrl+N opening new window in PWA.
+				// (No effect in a regular browser tab.)
+				e.preventDefault();
 			}
 
 			hostMessaging.postMessage('did-keydown', {
@@ -665,6 +669,24 @@
 			return hasMeta && e.key.toLowerCase() === 's';
 		}
 
+		/**
+		 * @param {KeyboardEvent} e
+		 * @return {boolean}
+		 */
+		function isCloseTab(e) {
+			const hasMeta = e.ctrlKey || e.metaKey;
+			return hasMeta && e.key.toLowerCase() === 'w';
+		}
+
+		/**
+		 * @param {KeyboardEvent} e
+		 * @return {boolean}
+		 */
+		function isNewWindow(e) {
+			const hasMeta = e.ctrlKey || e.metaKey;
+			return hasMeta && e.key.toLowerCase() === 'n';
+		}
+
 		let isHandlingScroll = false;
 
 		/**