src/vs/workbench/common/editor/textEditorModel.ts/BaseTextEditorModel/createTextEditorModel
class BaseTextEditorModel:	protected createTextEditorModel(value: ITextBufferFactory, resource: URI | undefined, preferredLanguageId?: string): ITextModel {
		const firstLineText = this.getFirstLineText(value);
		const languageSelection = this.getOrCreateLanguage(resource, this.languageService, preferredLanguageId, firstLineText);

		return this.doCreateTextEditorModel(value, languageSelection, resource);
	}