Don't take user file associations into account for webview mime types

Fixes #62892

src/vs/base/common/mime.ts

@@ -106,7 +106,7 @@ export function clearTextMimes(onlyUserConfigured?: boolean): void {
 /**
  * Given a file, return the best matching mime type for it
  */
-export function guessMimeTypes(path: string, firstLine?: string): string[] {
+export function guessMimeTypes(path: string, firstLine?: string, skipUserAssociations: boolean = false): string[] {
 	if (!path) {
 		return [MIME_UNKNOWN];
 	}
@@ -114,11 +114,13 @@ export function guessMimeTypes(path: string, firstLine?: string): string[] {
 	path = path.toLowerCase();
 	const filename = paths.basename(path);
 
+	if (!skipUserAssociations) {
 		// 1.) User configured mappings have highest priority
 		const configuredMime = guessMimeTypeByPath(path, filename, userRegisteredAssociations);
 		if (configuredMime) {
 			return [configuredMime, MIME_TEXT];
 		}
+	}
 
 	// 2.) Registered mappings have middle priority
 	const registeredMime = guessMimeTypeByPath(path, filename, nonUserRegisteredAssociations);

src/vs/workbench/parts/webview/electron-browser/webviewProtocols.ts

@@ -52,5 +52,5 @@ const webviewMimeTypes = {
 
 function getMimeType(normalizedPath: URI) {
 	const ext = extname(normalizedPath.fsPath).toLowerCase();
-	return webviewMimeTypes[ext] || getMediaMime(normalizedPath.fsPath) || guessMimeTypes(normalizedPath.fsPath)[0];
+	return webviewMimeTypes[ext] || getMediaMime(normalizedPath.fsPath) || guessMimeTypes(normalizedPath.fsPath, undefined, true)[0];
 }