constructor(compiledURL, sourceMappingURL, payload) {
        this.#json = payload;
        this.#compiledURLInternal = compiledURL;
        this.#sourceMappingURL = sourceMappingURL;
        this.#baseURL = (Common.ParsedURL.schemeIs(sourceMappingURL, 'data:')) ? compiledURL : sourceMappingURL;
        this.#mappingsInternal = null;
        if ('sections' in this.#json) {
            if (this.#json.sections.find(section => 'url' in section)) {
                console.warn(`SourceMap "${sourceMappingURL}" contains unsupported "URL" field in one of its sections.`);
            }
        }
        this.eachSection(this.parseSources.bind(this));
    }
@param {string} compiledURL
@param {string} sourceMappingURL
@param {object} payload
Implements Source Map V3 model. See https://github.com/google/closure-compiler/wiki/Source-Maps
for format description.