src/vs/editor/common/services/modelService.ts/ModelData/setLanguage
class ModelData:	public setLanguage(languageSelection: ILanguageSelection, source?: string): void {
		this._disposeLanguageSelection();
		this._languageSelection = languageSelection;
		this._languageSelectionListener = this._languageSelection.onDidChange(() => this.model.setMode(languageSelection.languageId, source));
		this.model.setMode(languageSelection.languageId, source);
	}