src/vs/workbench/common/editor/textResourceEditorInput.ts/TextResourceEditorInput/setLanguageId
class TextResourceEditorInput:	setLanguageId(languageId: string): void {
		this.setPreferredLanguageId(languageId);

		if (this.cachedModel) {
			this.cachedModel.setLanguageId(languageId);
		}
	}