Index: frontend/node_modules/abab/lib/atob.js
===================================================================
--- frontend/node_modules/abab/lib/atob.js	(revision 9af201e94b5a79beb92a30858fc54de4bc3b9449)
+++ frontend/node_modules/abab/lib/atob.js	(revision 9af201e94b5a79beb92a30858fc54de4bc3b9449)
@@ -0,0 +1,101 @@
+"use strict";
+
+/**
+ * Implementation of atob() according to the HTML and Infra specs, except that
+ * instead of throwing INVALID_CHARACTER_ERR we return null.
+ */
+function atob(data) {
+  if (arguments.length === 0) {
+    throw new TypeError("1 argument required, but only 0 present.");
+  }
+
+  // Web IDL requires DOMStrings to just be converted using ECMAScript
+  // ToString, which in our case amounts to using a template literal.
+  data = `${data}`;
+  // "Remove all ASCII whitespace from data."
+  data = data.replace(/[ \t\n\f\r]/g, "");
+  // "If data's length divides by 4 leaving no remainder, then: if data ends
+  // with one or two U+003D (=) code points, then remove them from data."
+  if (data.length % 4 === 0) {
+    data = data.replace(/==?$/, "");
+  }
+  // "If data's length divides by 4 leaving a remainder of 1, then return
+  // failure."
+  //
+  // "If data contains a code point that is not one of
+  //
+  // U+002B (+)
+  // U+002F (/)
+  // ASCII alphanumeric
+  //
+  // then return failure."
+  if (data.length % 4 === 1 || /[^+/0-9A-Za-z]/.test(data)) {
+    return null;
+  }
+  // "Let output be an empty byte sequence."
+  let output = "";
+  // "Let buffer be an empty buffer that can have bits appended to it."
+  //
+  // We append bits via left-shift and or.  accumulatedBits is used to track
+  // when we've gotten to 24 bits.
+  let buffer = 0;
+  let accumulatedBits = 0;
+  // "Let position be a position variable for data, initially pointing at the
+  // start of data."
+  //
+  // "While position does not point past the end of data:"
+  for (let i = 0; i < data.length; i++) {
+    // "Find the code point pointed to by position in the second column of
+    // Table 1: The Base 64 Alphabet of RFC 4648. Let n be the number given in
+    // the first cell of the same row.
+    //
+    // "Append to buffer the six bits corresponding to n, most significant bit
+    // first."
+    //
+    // atobLookup() implements the table from RFC 4648.
+    buffer <<= 6;
+    buffer |= atobLookup(data[i]);
+    accumulatedBits += 6;
+    // "If buffer has accumulated 24 bits, interpret them as three 8-bit
+    // big-endian numbers. Append three bytes with values equal to those
+    // numbers to output, in the same order, and then empty buffer."
+    if (accumulatedBits === 24) {
+      output += String.fromCharCode((buffer & 0xff0000) >> 16);
+      output += String.fromCharCode((buffer & 0xff00) >> 8);
+      output += String.fromCharCode(buffer & 0xff);
+      buffer = accumulatedBits = 0;
+    }
+    // "Advance position by 1."
+  }
+  // "If buffer is not empty, it contains either 12 or 18 bits. If it contains
+  // 12 bits, then discard the last four and interpret the remaining eight as
+  // an 8-bit big-endian number. If it contains 18 bits, then discard the last
+  // two and interpret the remaining 16 as two 8-bit big-endian numbers. Append
+  // the one or two bytes with values equal to those one or two numbers to
+  // output, in the same order."
+  if (accumulatedBits === 12) {
+    buffer >>= 4;
+    output += String.fromCharCode(buffer);
+  } else if (accumulatedBits === 18) {
+    buffer >>= 2;
+    output += String.fromCharCode((buffer & 0xff00) >> 8);
+    output += String.fromCharCode(buffer & 0xff);
+  }
+  // "Return output."
+  return output;
+}
+/**
+ * A lookup table for atob(), which converts an ASCII character to the
+ * corresponding six-bit number.
+ */
+
+const keystr =
+  "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
+
+function atobLookup(chr) {
+  const index = keystr.indexOf(chr);
+  // Throw exception if character is not in the lookup string; should not be hit in tests
+  return index < 0 ? undefined : index;
+}
+
+module.exports = atob;
Index: frontend/node_modules/abab/lib/btoa.js
===================================================================
--- frontend/node_modules/abab/lib/btoa.js	(revision 9af201e94b5a79beb92a30858fc54de4bc3b9449)
+++ frontend/node_modules/abab/lib/btoa.js	(revision 9af201e94b5a79beb92a30858fc54de4bc3b9449)
@@ -0,0 +1,62 @@
+"use strict";
+
+/**
+ * btoa() as defined by the HTML and Infra specs, which mostly just references
+ * RFC 4648.
+ */
+function btoa(s) {
+  if (arguments.length === 0) {
+    throw new TypeError("1 argument required, but only 0 present.");
+  }
+
+  let i;
+  // String conversion as required by Web IDL.
+  s = `${s}`;
+  // "The btoa() method must throw an "InvalidCharacterError" DOMException if
+  // data contains any character whose code point is greater than U+00FF."
+  for (i = 0; i < s.length; i++) {
+    if (s.charCodeAt(i) > 255) {
+      return null;
+    }
+  }
+  let out = "";
+  for (i = 0; i < s.length; i += 3) {
+    const groupsOfSix = [undefined, undefined, undefined, undefined];
+    groupsOfSix[0] = s.charCodeAt(i) >> 2;
+    groupsOfSix[1] = (s.charCodeAt(i) & 0x03) << 4;
+    if (s.length > i + 1) {
+      groupsOfSix[1] |= s.charCodeAt(i + 1) >> 4;
+      groupsOfSix[2] = (s.charCodeAt(i + 1) & 0x0f) << 2;
+    }
+    if (s.length > i + 2) {
+      groupsOfSix[2] |= s.charCodeAt(i + 2) >> 6;
+      groupsOfSix[3] = s.charCodeAt(i + 2) & 0x3f;
+    }
+    for (let j = 0; j < groupsOfSix.length; j++) {
+      if (typeof groupsOfSix[j] === "undefined") {
+        out += "=";
+      } else {
+        out += btoaLookup(groupsOfSix[j]);
+      }
+    }
+  }
+  return out;
+}
+
+/**
+ * Lookup table for btoa(), which converts a six-bit number into the
+ * corresponding ASCII character.
+ */
+const keystr =
+  "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
+
+function btoaLookup(index) {
+  if (index >= 0 && index < 64) {
+    return keystr[index];
+  }
+
+  // Throw INVALID_CHARACTER_ERR exception here -- won't be hit in the tests.
+  return undefined;
+}
+
+module.exports = btoa;