src/vs/editor/common/services/languagesRegistry.ts/LanguagesRegistry/guessLanguageIdByFilepathOrFirstLine
class LanguagesRegistry:	public guessLanguageIdByFilepathOrFirstLine(resource: URI | null, firstLine?: string): string[] {
		if (!resource && !firstLine) {
			return [];
		}
		return getLanguageIds(resource, firstLine);
	}