src/vs/workbench/api/browser/mainThreadDocuments.ts/MainThreadDocuments/_onModelModeChanged
class MainThreadDocuments:	private _onModelModeChanged(event: { model: ITextModel; oldModeId: string; }): void {
		let { model } = event;
		if (!this._modelIsSynced.has(model.uri)) {
			return;
		}
		this._proxy.$acceptModelModeChanged(model.uri, model.getLanguageIdentifier().language);
	}