Revert "remove unused isBuiltin-flag when registering a feature, #15411"

This reverts commit 21b5a17.

src/vs/editor/common/modes/languageFeatureRegistry.ts

@@ -13,6 +13,7 @@ import { LanguageSelector, score } from 'vs/editor/common/modes/languageSelector
 interface Entry<T> {
 	selector: LanguageSelector;
 	provider: T;
+	isBuiltin: boolean;
 	_score: number;
 	_time: number;
 }
@@ -30,11 +31,12 @@ export default class LanguageFeatureRegistry<T> {
 		return this._onDidChange.event;
 	}
 
-	register(selector: LanguageSelector, provider: T): IDisposable {
+	register(selector: LanguageSelector, provider: T, isBuiltin = false): IDisposable {
 
 		let entry: Entry<T> = {
 			selector,
 			provider,
+			isBuiltin,
 			_score: -1,
 			_time: this._clock++
 		};
@@ -141,6 +143,10 @@ export default class LanguageFeatureRegistry<T> {
 
 		for (let entry of this._entries) {
 			entry._score = score(entry.selector, model.uri, model.getModeId());
+			if (entry.isBuiltin && entry._score > 0) {
+				entry._score = .5;
+				entry._time = -1;
+			}
 		}
 
 		// needs sorting