src/vs/workbench/services/themes/browser/fileIconThemeData.ts/FileIconThemeLoader/loadIconThemeDocument
class FileIconThemeLoader:	private loadIconThemeDocument(location: URI): Promise<IconThemeDocument> {
		return this.fileService.readExtensionResource(location).then((content) => {
			const errors: Json.ParseError[] = [];
			const contentValue = Json.parse(content, errors);
			if (errors.length > 0) {
				return Promise.reject(new Error(nls.localize('error.cannotparseicontheme', "Problems parsing file icons file: {0}", errors.map(e => getParseErrorMessage(e.error)).join(', '))));
			} else if (Json.getNodeType(contentValue) !== 'object') {
				return Promise.reject(new Error(nls.localize('error.invalidformat', "Invalid format for file icons theme file: Object expected.")));
			}
			return Promise.resolve(contentValue);
		});
	}