src/vs/platform/theme/common/iconRegistry.ts/stringOrUndef
	export function fromJSONObject(json: any): IconFontDefinition | undefined {
		const stringOrUndef = (s: any) => isString(s) ? s : undefined;
		if (json && Array.isArray(json.src) && json.src.every((s: any) => isString(s.format) && isString(s.location))) {
			return {
				weight: stringOrUndef(json.weight),
				style: stringOrUndef(json.style),
				src: json.src.map((s: any) => ({ format: s.format, location: URI.parse(s.location) }))
			};
		}
		return undefined;
	}