src/vs/workbench/common/editor/textEditorModel.ts/BaseTextEditorModel/installModelListeners
class BaseTextEditorModel:	protected installModelListeners(model: ITextModel): void {

		// Setup listener for lower level language changes
		const disposable = this._register(model.onDidChangeLanguage((e) => {
			if (e.source === LanguageDetectionLanguageEventSource) {
				return;
			}

			this._hasLanguageSetExplicitly = true;
			disposable.dispose();
		}));
	}