Index: frontend/node_modules/istanbul-lib-source-maps/lib/get-mapping.js
===================================================================
--- frontend/node_modules/istanbul-lib-source-maps/lib/get-mapping.js	(revision 9af201e94b5a79beb92a30858fc54de4bc3b9449)
+++ frontend/node_modules/istanbul-lib-source-maps/lib/get-mapping.js	(revision 9af201e94b5a79beb92a30858fc54de4bc3b9449)
@@ -0,0 +1,182 @@
+/*
+ Copyright 2015, Yahoo Inc.
+ Copyrights licensed under the New BSD License. See the accompanying LICENSE file for terms.
+ */
+'use strict';
+
+const pathutils = require('./pathutils');
+const {
+    GREATEST_LOWER_BOUND,
+    LEAST_UPPER_BOUND
+} = require('source-map').SourceMapConsumer;
+
+/**
+ * AST ranges are inclusive for start positions and exclusive for end positions.
+ * Source maps are also logically ranges over text, though interacting with
+ * them is generally achieved by working with explicit positions.
+ *
+ * When finding the _end_ location of an AST item, the range behavior is
+ * important because what we're asking for is the _end_ of whatever range
+ * corresponds to the end location we seek.
+ *
+ * This boils down to the following steps, conceptually, though the source-map
+ * library doesn't expose primitives to do this nicely:
+ *
+ * 1. Find the range on the generated file that ends at, or exclusively
+ *    contains the end position of the AST node.
+ * 2. Find the range on the original file that corresponds to
+ *    that generated range.
+ * 3. Find the _end_ location of that original range.
+ */
+function originalEndPositionFor(sourceMap, generatedEnd) {
+    // Given the generated location, find the original location of the mapping
+    // that corresponds to a range on the generated file that overlaps the
+    // generated file end location. Note however that this position on its
+    // own is not useful because it is the position of the _start_ of the range
+    // on the original file, and we want the _end_ of the range.
+    const beforeEndMapping = originalPositionTryBoth(
+        sourceMap,
+        generatedEnd.line,
+        generatedEnd.column - 1
+    );
+    if (beforeEndMapping.source === null) {
+        return null;
+    }
+
+    // Convert that original position back to a generated one, with a bump
+    // to the right, and a rightward bias. Since 'generatedPositionFor' searches
+    // for mappings in the original-order sorted list, this will find the
+    // mapping that corresponds to the one immediately after the
+    // beforeEndMapping mapping.
+    const afterEndMapping = sourceMap.generatedPositionFor({
+        source: beforeEndMapping.source,
+        line: beforeEndMapping.line,
+        column: beforeEndMapping.column + 1,
+        bias: LEAST_UPPER_BOUND
+    });
+    if (
+        // If this is null, it means that we've hit the end of the file,
+        // so we can use Infinity as the end column.
+        afterEndMapping.line === null ||
+        // If these don't match, it means that the call to
+        // 'generatedPositionFor' didn't find any other original mappings on
+        // the line we gave, so consider the binding to extend to infinity.
+        sourceMap.originalPositionFor(afterEndMapping).line !==
+            beforeEndMapping.line
+    ) {
+        return {
+            source: beforeEndMapping.source,
+            line: beforeEndMapping.line,
+            column: Infinity
+        };
+    }
+
+    // Convert the end mapping into the real original position.
+    return sourceMap.originalPositionFor(afterEndMapping);
+}
+
+/**
+ * Attempts to determine the original source position, first
+ * returning the closest element to the left (GREATEST_LOWER_BOUND),
+ * and next returning the closest element to the right (LEAST_UPPER_BOUND).
+ */
+function originalPositionTryBoth(sourceMap, line, column) {
+    const mapping = sourceMap.originalPositionFor({
+        line,
+        column,
+        bias: GREATEST_LOWER_BOUND
+    });
+    if (mapping.source === null) {
+        return sourceMap.originalPositionFor({
+            line,
+            column,
+            bias: LEAST_UPPER_BOUND
+        });
+    } else {
+        return mapping;
+    }
+}
+
+function isInvalidPosition(pos) {
+    return (
+        !pos ||
+        typeof pos.line !== 'number' ||
+        typeof pos.column !== 'number' ||
+        pos.line < 0 ||
+        pos.column < 0
+    );
+}
+
+/**
+ * determines the original position for a given location
+ * @param  {SourceMapConsumer} sourceMap the source map
+ * @param  {Object} generatedLocation the original location Object
+ * @returns {Object} the remapped location Object
+ */
+function getMapping(sourceMap, generatedLocation, origFile) {
+    if (!generatedLocation) {
+        return null;
+    }
+
+    if (
+        isInvalidPosition(generatedLocation.start) ||
+        isInvalidPosition(generatedLocation.end)
+    ) {
+        return null;
+    }
+
+    const start = originalPositionTryBoth(
+        sourceMap,
+        generatedLocation.start.line,
+        generatedLocation.start.column
+    );
+    let end = originalEndPositionFor(sourceMap, generatedLocation.end);
+
+    /* istanbul ignore if: edge case too hard to test for */
+    if (!(start && end)) {
+        return null;
+    }
+
+    if (!(start.source && end.source)) {
+        return null;
+    }
+
+    if (start.source !== end.source) {
+        return null;
+    }
+
+    /* istanbul ignore if: edge case too hard to test for */
+    if (start.line === null || start.column === null) {
+        return null;
+    }
+
+    /* istanbul ignore if: edge case too hard to test for */
+    if (end.line === null || end.column === null) {
+        return null;
+    }
+
+    if (start.line === end.line && start.column === end.column) {
+        end = sourceMap.originalPositionFor({
+            line: generatedLocation.end.line,
+            column: generatedLocation.end.column,
+            bias: LEAST_UPPER_BOUND
+        });
+        end.column -= 1;
+    }
+
+    return {
+        source: pathutils.relativeTo(start.source, origFile),
+        loc: {
+            start: {
+                line: start.line,
+                column: start.column
+            },
+            end: {
+                line: end.line,
+                column: end.column
+            }
+        }
+    };
+}
+
+module.exports = getMapping;
Index: frontend/node_modules/istanbul-lib-source-maps/lib/map-store.js
===================================================================
--- frontend/node_modules/istanbul-lib-source-maps/lib/map-store.js	(revision 9af201e94b5a79beb92a30858fc54de4bc3b9449)
+++ frontend/node_modules/istanbul-lib-source-maps/lib/map-store.js	(revision 9af201e94b5a79beb92a30858fc54de4bc3b9449)
@@ -0,0 +1,226 @@
+/*
+ Copyright 2015, Yahoo Inc.
+ Copyrights licensed under the New BSD License. See the accompanying LICENSE file for terms.
+ */
+'use strict';
+
+const path = require('path');
+const fs = require('fs');
+const debug = require('debug')('istanbuljs');
+const { SourceMapConsumer } = require('source-map');
+const pathutils = require('./pathutils');
+const { SourceMapTransformer } = require('./transformer');
+
+/**
+ * Tracks source maps for registered files
+ */
+class MapStore {
+    /**
+     * @param {Object} opts [opts=undefined] options.
+     * @param {Boolean} opts.verbose [opts.verbose=false] verbose mode
+     * @param {String} opts.baseDir [opts.baseDir=null] alternate base directory
+     *  to resolve sourcemap files
+     * @param {Class} opts.SourceStore [opts.SourceStore=Map] class to use for
+     * SourceStore.  Must support `get`, `set` and `clear` methods.
+     * @param {Array} opts.sourceStoreOpts [opts.sourceStoreOpts=[]] arguments
+     * to use in the SourceStore constructor.
+     * @constructor
+     */
+    constructor(opts) {
+        opts = {
+            baseDir: null,
+            verbose: false,
+            SourceStore: Map,
+            sourceStoreOpts: [],
+            ...opts
+        };
+        this.baseDir = opts.baseDir;
+        this.verbose = opts.verbose;
+        this.sourceStore = new opts.SourceStore(...opts.sourceStoreOpts);
+        this.data = Object.create(null);
+        this.sourceFinder = this.sourceFinder.bind(this);
+    }
+
+    /**
+     * Registers a source map URL with this store. It makes some input sanity checks
+     * and silently fails on malformed input.
+     * @param transformedFilePath - the file path for which the source map is valid.
+     *  This must *exactly* match the path stashed for the coverage object to be
+     *  useful.
+     * @param sourceMapUrl - the source map URL, **not** a comment
+     */
+    registerURL(transformedFilePath, sourceMapUrl) {
+        const d = 'data:';
+
+        if (
+            sourceMapUrl.length > d.length &&
+            sourceMapUrl.substring(0, d.length) === d
+        ) {
+            const b64 = 'base64,';
+            const pos = sourceMapUrl.indexOf(b64);
+            if (pos > 0) {
+                this.data[transformedFilePath] = {
+                    type: 'encoded',
+                    data: sourceMapUrl.substring(pos + b64.length)
+                };
+            } else {
+                debug(`Unable to interpret source map URL: ${sourceMapUrl}`);
+            }
+
+            return;
+        }
+
+        const dir = path.dirname(path.resolve(transformedFilePath));
+        const file = path.resolve(dir, sourceMapUrl);
+        this.data[transformedFilePath] = { type: 'file', data: file };
+    }
+
+    /**
+     * Registers a source map object with this store. Makes some basic sanity checks
+     * and silently fails on malformed input.
+     * @param transformedFilePath - the file path for which the source map is valid
+     * @param sourceMap - the source map object
+     */
+    registerMap(transformedFilePath, sourceMap) {
+        if (sourceMap && sourceMap.version) {
+            this.data[transformedFilePath] = {
+                type: 'object',
+                data: sourceMap
+            };
+        } else {
+            debug(
+                'Invalid source map object: ' +
+                    JSON.stringify(sourceMap, null, 2)
+            );
+        }
+    }
+
+    /**
+     * Retrieve a source map object from this store.
+     * @param filePath - the file path for which the source map is valid
+     * @returns {Object} a parsed source map object
+     */
+    getSourceMapSync(filePath) {
+        try {
+            if (!this.data[filePath]) {
+                return;
+            }
+
+            const d = this.data[filePath];
+            if (d.type === 'file') {
+                return JSON.parse(fs.readFileSync(d.data, 'utf8'));
+            }
+
+            if (d.type === 'encoded') {
+                return JSON.parse(Buffer.from(d.data, 'base64').toString());
+            }
+
+            /* The caller might delete properties */
+            return {
+                ...d.data
+            };
+        } catch (error) {
+            debug('Error returning source map for ' + filePath);
+            debug(error.stack);
+
+            return;
+        }
+    }
+
+    /**
+     * Add inputSourceMap property to coverage data
+     * @param coverageData - the __coverage__ object
+     * @returns {Object} a parsed source map object
+     */
+    addInputSourceMapsSync(coverageData) {
+        Object.entries(coverageData).forEach(([filePath, data]) => {
+            if (data.inputSourceMap) {
+                return;
+            }
+
+            const sourceMap = this.getSourceMapSync(filePath);
+            if (sourceMap) {
+                data.inputSourceMap = sourceMap;
+                /* This huge property is not needed. */
+                delete data.inputSourceMap.sourcesContent;
+            }
+        });
+    }
+
+    sourceFinder(filePath) {
+        const content = this.sourceStore.get(filePath);
+        if (content !== undefined) {
+            return content;
+        }
+
+        if (path.isAbsolute(filePath)) {
+            return fs.readFileSync(filePath, 'utf8');
+        }
+
+        return fs.readFileSync(
+            pathutils.asAbsolute(filePath, this.baseDir),
+            'utf8'
+        );
+    }
+
+    /**
+     * Transforms the coverage map provided into one that refers to original
+     * sources when valid mappings have been registered with this store.
+     * @param {CoverageMap} coverageMap - the coverage map to transform
+     * @returns {Promise<CoverageMap>} the transformed coverage map
+     */
+    async transformCoverage(coverageMap) {
+        const hasInputSourceMaps = coverageMap
+            .files()
+            .some(
+                file => coverageMap.fileCoverageFor(file).data.inputSourceMap
+            );
+
+        if (!hasInputSourceMaps && Object.keys(this.data).length === 0) {
+            return coverageMap;
+        }
+
+        const transformer = new SourceMapTransformer(
+            async (filePath, coverage) => {
+                try {
+                    const obj =
+                        coverage.data.inputSourceMap ||
+                        this.getSourceMapSync(filePath);
+                    if (!obj) {
+                        return null;
+                    }
+
+                    const smc = new SourceMapConsumer(obj);
+                    smc.sources.forEach(s => {
+                        const content = smc.sourceContentFor(s);
+                        if (content) {
+                            const sourceFilePath = pathutils.relativeTo(
+                                s,
+                                filePath
+                            );
+                            this.sourceStore.set(sourceFilePath, content);
+                        }
+                    });
+
+                    return smc;
+                } catch (error) {
+                    debug('Error returning source map for ' + filePath);
+                    debug(error.stack);
+
+                    return null;
+                }
+            }
+        );
+
+        return await transformer.transform(coverageMap);
+    }
+
+    /**
+     * Disposes temporary resources allocated by this map store
+     */
+    dispose() {
+        this.sourceStore.clear();
+    }
+}
+
+module.exports = { MapStore };
Index: frontend/node_modules/istanbul-lib-source-maps/lib/mapped.js
===================================================================
--- frontend/node_modules/istanbul-lib-source-maps/lib/mapped.js	(revision 9af201e94b5a79beb92a30858fc54de4bc3b9449)
+++ frontend/node_modules/istanbul-lib-source-maps/lib/mapped.js	(revision 9af201e94b5a79beb92a30858fc54de4bc3b9449)
@@ -0,0 +1,113 @@
+/*
+ Copyright 2015, Yahoo Inc.
+ Copyrights licensed under the New BSD License. See the accompanying LICENSE file for terms.
+ */
+'use strict';
+
+const { FileCoverage } = require('istanbul-lib-coverage').classes;
+
+function locString(loc) {
+    return [
+        loc.start.line,
+        loc.start.column,
+        loc.end.line,
+        loc.end.column
+    ].join(':');
+}
+
+class MappedCoverage extends FileCoverage {
+    constructor(pathOrObj) {
+        super(pathOrObj);
+
+        this.meta = {
+            last: {
+                s: 0,
+                f: 0,
+                b: 0
+            },
+            seen: {}
+        };
+    }
+
+    addStatement(loc, hits) {
+        const key = 's:' + locString(loc);
+        const { meta } = this;
+        let index = meta.seen[key];
+
+        if (index === undefined) {
+            index = meta.last.s;
+            meta.last.s += 1;
+            meta.seen[key] = index;
+            this.statementMap[index] = this.cloneLocation(loc);
+        }
+
+        this.s[index] = this.s[index] || 0;
+        this.s[index] += hits;
+        return index;
+    }
+
+    addFunction(name, decl, loc, hits) {
+        const key = 'f:' + locString(decl);
+        const { meta } = this;
+        let index = meta.seen[key];
+
+        if (index === undefined) {
+            index = meta.last.f;
+            meta.last.f += 1;
+            meta.seen[key] = index;
+            name = name || `(unknown_${index})`;
+            this.fnMap[index] = {
+                name,
+                decl: this.cloneLocation(decl),
+                loc: this.cloneLocation(loc)
+            };
+        }
+
+        this.f[index] = this.f[index] || 0;
+        this.f[index] += hits;
+        return index;
+    }
+
+    addBranch(type, loc, branchLocations, hits) {
+        const key = ['b', ...branchLocations.map(l => locString(l))].join(':');
+        const { meta } = this;
+        let index = meta.seen[key];
+        if (index === undefined) {
+            index = meta.last.b;
+            meta.last.b += 1;
+            meta.seen[key] = index;
+            this.branchMap[index] = {
+                loc,
+                type,
+                locations: branchLocations.map(l => this.cloneLocation(l))
+            };
+        }
+
+        if (!this.b[index]) {
+            this.b[index] = branchLocations.map(() => 0);
+        }
+
+        hits.forEach((hit, i) => {
+            this.b[index][i] += hit;
+        });
+        return index;
+    }
+
+    /* Returns a clone of the location object with only the attributes of interest */
+    cloneLocation(loc) {
+        return {
+            start: {
+                line: loc.start.line,
+                column: loc.start.column
+            },
+            end: {
+                line: loc.end.line,
+                column: loc.end.column
+            }
+        };
+    }
+}
+
+module.exports = {
+    MappedCoverage
+};
Index: frontend/node_modules/istanbul-lib-source-maps/lib/pathutils.js
===================================================================
--- frontend/node_modules/istanbul-lib-source-maps/lib/pathutils.js	(revision 9af201e94b5a79beb92a30858fc54de4bc3b9449)
+++ frontend/node_modules/istanbul-lib-source-maps/lib/pathutils.js	(revision 9af201e94b5a79beb92a30858fc54de4bc3b9449)
@@ -0,0 +1,21 @@
+/*
+ Copyright 2015, Yahoo Inc.
+ Copyrights licensed under the New BSD License. See the accompanying LICENSE file for terms.
+ */
+'use strict';
+
+const path = require('path');
+
+module.exports = {
+    isAbsolute: path.isAbsolute,
+    asAbsolute(file, baseDir) {
+        return path.isAbsolute(file)
+            ? file
+            : path.resolve(baseDir || process.cwd(), file);
+    },
+    relativeTo(file, origFile) {
+        return path.isAbsolute(file)
+            ? file
+            : path.resolve(path.dirname(origFile), file);
+    }
+};
Index: frontend/node_modules/istanbul-lib-source-maps/lib/transform-utils.js
===================================================================
--- frontend/node_modules/istanbul-lib-source-maps/lib/transform-utils.js	(revision 9af201e94b5a79beb92a30858fc54de4bc3b9449)
+++ frontend/node_modules/istanbul-lib-source-maps/lib/transform-utils.js	(revision 9af201e94b5a79beb92a30858fc54de4bc3b9449)
@@ -0,0 +1,21 @@
+/*
+ Copyright 2015, Yahoo Inc.
+ Copyrights licensed under the New BSD License. See the accompanying LICENSE file for terms.
+ */
+'use strict';
+
+function getUniqueKey(pathname) {
+    return pathname.replace(/[\\/]/g, '_');
+}
+
+function getOutput(cache) {
+    return Object.values(cache).reduce(
+        (output, { file, mappedCoverage }) => ({
+            ...output,
+            [file]: mappedCoverage
+        }),
+        {}
+    );
+}
+
+module.exports = { getUniqueKey, getOutput };
Index: frontend/node_modules/istanbul-lib-source-maps/lib/transformer.js
===================================================================
--- frontend/node_modules/istanbul-lib-source-maps/lib/transformer.js	(revision 9af201e94b5a79beb92a30858fc54de4bc3b9449)
+++ frontend/node_modules/istanbul-lib-source-maps/lib/transformer.js	(revision 9af201e94b5a79beb92a30858fc54de4bc3b9449)
@@ -0,0 +1,147 @@
+/*
+ Copyright 2015, Yahoo Inc.
+ Copyrights licensed under the New BSD License. See the accompanying LICENSE file for terms.
+ */
+'use strict';
+
+const debug = require('debug')('istanbuljs');
+const libCoverage = require('istanbul-lib-coverage');
+const { MappedCoverage } = require('./mapped');
+const getMapping = require('./get-mapping');
+const { getUniqueKey, getOutput } = require('./transform-utils');
+
+class SourceMapTransformer {
+    constructor(finder, opts = {}) {
+        this.finder = finder;
+        this.baseDir = opts.baseDir || process.cwd();
+        this.resolveMapping = opts.getMapping || getMapping;
+    }
+
+    processFile(fc, sourceMap, coverageMapper) {
+        let changes = 0;
+
+        Object.entries(fc.statementMap).forEach(([s, loc]) => {
+            const hits = fc.s[s];
+            const mapping = this.resolveMapping(sourceMap, loc, fc.path);
+
+            if (mapping) {
+                changes += 1;
+                const mappedCoverage = coverageMapper(mapping.source);
+                mappedCoverage.addStatement(mapping.loc, hits);
+            }
+        });
+
+        Object.entries(fc.fnMap).forEach(([f, fnMeta]) => {
+            const hits = fc.f[f];
+            const mapping = this.resolveMapping(
+                sourceMap,
+                fnMeta.decl,
+                fc.path
+            );
+
+            const spanMapping = this.resolveMapping(
+                sourceMap,
+                fnMeta.loc,
+                fc.path
+            );
+
+            if (
+                mapping &&
+                spanMapping &&
+                mapping.source === spanMapping.source
+            ) {
+                changes += 1;
+                const mappedCoverage = coverageMapper(mapping.source);
+                mappedCoverage.addFunction(
+                    fnMeta.name,
+                    mapping.loc,
+                    spanMapping.loc,
+                    hits
+                );
+            }
+        });
+
+        Object.entries(fc.branchMap).forEach(([b, branchMeta]) => {
+            const hits = fc.b[b];
+            const locs = [];
+            const mappedHits = [];
+            let source;
+            let skip;
+
+            branchMeta.locations.forEach((loc, i) => {
+                const mapping = this.resolveMapping(sourceMap, loc, fc.path);
+                if (mapping) {
+                    if (!source) {
+                        source = mapping.source;
+                    }
+
+                    if (mapping.source !== source) {
+                        skip = true;
+                    }
+
+                    locs.push(mapping.loc);
+                    mappedHits.push(hits[i]);
+                }
+            });
+
+            const locMapping = branchMeta.loc
+                ? this.resolveMapping(sourceMap, branchMeta.loc, fc.path)
+                : null;
+
+            if (!skip && locs.length > 0) {
+                changes += 1;
+                const mappedCoverage = coverageMapper(source);
+                mappedCoverage.addBranch(
+                    branchMeta.type,
+                    locMapping ? locMapping.loc : locs[0],
+                    locs,
+                    mappedHits
+                );
+            }
+        });
+
+        return changes > 0;
+    }
+
+    async transform(coverageMap) {
+        const uniqueFiles = {};
+        const getMappedCoverage = file => {
+            const key = getUniqueKey(file);
+            if (!uniqueFiles[key]) {
+                uniqueFiles[key] = {
+                    file,
+                    mappedCoverage: new MappedCoverage(file)
+                };
+            }
+
+            return uniqueFiles[key].mappedCoverage;
+        };
+
+        for (const file of coverageMap.files()) {
+            const fc = coverageMap.fileCoverageFor(file);
+            const sourceMap = await this.finder(file, fc);
+
+            if (sourceMap) {
+                const changed = this.processFile(
+                    fc,
+                    sourceMap,
+                    getMappedCoverage
+                );
+                if (!changed) {
+                    debug(`File [${file}] ignored, nothing could be mapped`);
+                }
+            } else {
+                uniqueFiles[getUniqueKey(file)] = {
+                    file,
+                    mappedCoverage: new MappedCoverage(fc)
+                };
+            }
+        }
+
+        return libCoverage.createCoverageMap(getOutput(uniqueFiles));
+    }
+}
+
+module.exports = {
+    SourceMapTransformer
+};