Adding upstream version 115.7.0esr.upstream/115.7.0esr

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

29 files changed, 6605 insertions, 0 deletions

diff --git a/toolkit/components/aboutmemory/content/aboutMemory.css b/toolkit/components/aboutmemory/content/aboutMemory.css
new file mode 100644
index 0000000000..cee0736b6e
--- /dev/null
+++ b/toolkit/components/aboutmemory/content/aboutMemory.css
@@ -0,0 +1,188 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/*
+ * The version used for mobile is located at
+ * toolkit/themes/mobile/global/aboutMemory.css.
+ * Desktop-specific stuff is at the bottom of this file.
+ */
+
+html {
+  background: -moz-Dialog;
+  color: -moz-DialogText;
+  font: message-box;
+}
+
+body {
+  padding: 0 2em;
+  min-width: 45em;
+  margin: auto;
+}
+
+/* The comment at the top of aboutMemory.xhtml explains this font choice. */
+pre {
+  font-family: DejaVu Sans Mono, Liberation Mono, Fira Mono, monospace;
+}
+
+div.ancillary {
+  margin: 0.5em 0;
+  user-select: none;
+}
+
+div.section {
+  padding: 2em;
+  margin: 1em 0em;
+  border: 1px solid ThreeDShadow;
+  border-radius: 10px;
+  background: Field;
+  color: FieldText;
+}
+
+div.outputContainer {
+  display: flex;
+}
+
+div.sections {
+  flex: 1;
+  min-width: 0;
+}
+
+div.sidebar {
+  flex: 0 0 max-content;
+  margin-left: 1em;
+}
+
+div.sidebarContents {
+  position: sticky;
+  top: 0.5em;
+}
+
+div.sidebarItem {
+  padding: 0.5em;
+  margin: 1em 0em;
+  border: 1px solid ThreeDShadow;
+  border-radius: 10px;
+  background: Field;
+  color: FieldText;
+  user-select: none;  /* no need to include this when cutting+pasting */
+}
+
+input.filterInput {
+  width: calc(100% - 1em);
+}
+
+ul.index {
+  list-style-position: inside;
+  margin: 0;
+  padding: 0;
+}
+
+ul.index > li {
+  padding-left: 0.5em;
+}
+
+div.opsRow {
+  padding: 0.5em;
+  margin-right: 0.5em;
+  margin-top: 0.5em;
+  border: 1px solid ThreeDShadow;
+  border-radius: 10px;
+  background: Field;
+  color: FieldText;
+  display: inline-block;
+}
+
+div.opsRowLabel, div.sidebarLabel {
+  display: block;
+  margin-bottom: 0.2em;
+  font-weight: bold;
+}
+
+.opsRowLabel label {
+  margin-left: 1em;
+  font-weight: normal;
+}
+
+div.non-verbose pre.entries {
+  overflow-x: hidden;
+  text-overflow: ellipsis;
+}
+
+h1 {
+  padding: 0;
+  margin: 0;
+  background: inherit; /* When sticky give it the solid background of the parent */
+  display: inline;  /* allow subsequent text to the right of the heading */
+  position: sticky; /* Stay at the top of the page when scrolling */
+  top: 0;
+  z-index: 1; /* When sticky it should appear above the tree lines */
+}
+
+h2 {
+  padding-left: .1em;
+}
+
+h3 {
+  display: inline;  /* allow subsequent text to the right of the heading */
+}
+
+a.upDownArrow {
+  font-size: 130%;
+  text-decoration: none;
+  user-select: none;  /* no need to include this when cutting+pasting */
+}
+
+.accuracyWarning, .badInputWarning, .invalid {
+  /*
+   * Technically this should be used with the default background colour,
+   * instead we're using the default field background colour,
+   * I hope this will be okay.
+   */
+  color: -moz-activehyperlinktext;
+}
+
+.treeline {
+  color: FieldText;
+  opacity: 0.5;
+}
+
+.mrValue {
+  font-weight: bold;
+}
+
+.hasKids {
+  cursor: pointer;
+}
+
+.hasKids:hover {
+  text-decoration: underline;
+}
+
+.noselect {
+  user-select: none;  /* no need to include this when cutting+pasting */
+}
+
+.option {
+  font-size: 80%;
+  user-select: none;  /* no need to include this when cutting+pasting */
+}
+
+.legend {
+  font-size: 80%;
+  user-select: none;  /* no need to include this when cutting+pasting */
+}
+
+.debug {
+  font-size: 80%;
+}
+
+.hidden {
+  display: none;
+}
+
+/* Desktop-specific parts go here. */
+
+.hasKids:hover {
+  text-decoration: underline;
+}
diff --git a/toolkit/components/aboutmemory/content/aboutMemory.js b/toolkit/components/aboutmemory/content/aboutMemory.js
new file mode 100644
index 0000000000..c1b7986781
--- /dev/null
+++ b/toolkit/components/aboutmemory/content/aboutMemory.js
@@ -0,0 +1,2483 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*-*/
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// You can direct about:memory to immediately load memory reports from a file
+// by providing a file= query string.  For example,
+//
+//     about:memory?file=/home/username/reports.json.gz
+//
+// "file=" is not case-sensitive.  We'll URI-unescape the contents of the
+// "file=" argument, and obviously the filename is case-sensitive iff you're on
+// a case-sensitive filesystem.  If you specify more than one "file=" argument,
+// only the first one is used.
+
+"use strict";
+
+// ---------------------------------------------------------------------------
+
+let CC = Components.Constructor;
+
+const KIND_NONHEAP = Ci.nsIMemoryReporter.KIND_NONHEAP;
+const KIND_HEAP = Ci.nsIMemoryReporter.KIND_HEAP;
+const KIND_OTHER = Ci.nsIMemoryReporter.KIND_OTHER;
+
+const UNITS_BYTES = Ci.nsIMemoryReporter.UNITS_BYTES;
+const UNITS_COUNT = Ci.nsIMemoryReporter.UNITS_COUNT;
+const UNITS_COUNT_CUMULATIVE = Ci.nsIMemoryReporter.UNITS_COUNT_CUMULATIVE;
+const UNITS_PERCENTAGE = Ci.nsIMemoryReporter.UNITS_PERCENTAGE;
+
+const { XPCOMUtils } = ChromeUtils.importESModule(
+  "resource://gre/modules/XPCOMUtils.sys.mjs"
+);
+const { NetUtil } = ChromeUtils.import("resource://gre/modules/NetUtil.jsm");
+ChromeUtils.defineESModuleGetters(this, {
+  Downloads: "resource://gre/modules/Downloads.sys.mjs",
+  FileUtils: "resource://gre/modules/FileUtils.sys.mjs",
+});
+
+XPCOMUtils.defineLazyGetter(this, "nsBinaryStream", () =>
+  CC(
+    "@mozilla.org/binaryinputstream;1",
+    "nsIBinaryInputStream",
+    "setInputStream"
+  )
+);
+XPCOMUtils.defineLazyGetter(this, "nsFile", () =>
+  CC("@mozilla.org/file/local;1", "nsIFile", "initWithPath")
+);
+XPCOMUtils.defineLazyGetter(this, "nsGzipConverter", () =>
+  CC(
+    "@mozilla.org/streamconv;1?from=gzip&to=uncompressed",
+    "nsIStreamConverter"
+  )
+);
+
+let gMgr = Cc["@mozilla.org/memory-reporter-manager;1"].getService(
+  Ci.nsIMemoryReporterManager
+);
+
+const gPageName = "about:memory";
+document.title = gPageName;
+
+const gMainProcessPrefix = "Main Process";
+
+const gFilterUpdateDelayMS = 300;
+
+let gIsDiff = false;
+
+let gCurrentReports = [];
+let gCurrentHasMozMallocUsableSize = false;
+let gCurrentIsDiff = false;
+
+let gFilter = "";
+
+// ---------------------------------------------------------------------------
+
+// Forward slashes in URLs in paths are represented with backslashes to avoid
+// being mistaken for path separators.  Paths/names where this hasn't been
+// undone are prefixed with "unsafe"; the rest are prefixed with "safe".
+function flipBackslashes(aUnsafeStr) {
+  // Save memory by only doing the replacement if it's necessary.
+  return !aUnsafeStr.includes("\\")
+    ? aUnsafeStr
+    : aUnsafeStr.replace(/\\/g, "/");
+}
+
+const gAssertionFailureMsgPrefix = "aboutMemory.js assertion failed: ";
+
+// This is used for things that should never fail, and indicate a defect in
+// this file if they do.
+function assert(aCond, aMsg) {
+  if (!aCond) {
+    reportAssertionFailure(aMsg);
+    throw new Error(gAssertionFailureMsgPrefix + aMsg);
+  }
+}
+
+// This is used for malformed input from memory reporters.
+function assertInput(aCond, aMsg) {
+  if (!aCond) {
+    throw new Error(`Invalid memory report(s): ${aMsg}`);
+  }
+}
+
+function handleException(aEx) {
+  let str = "" + aEx;
+  if (str.startsWith(gAssertionFailureMsgPrefix)) {
+    // Argh, assertion failure within this file!  Give up.
+    throw aEx;
+  } else {
+    // File or memory reporter problem.  Print a message.
+    updateMainAndFooter(str, NO_TIMESTAMP, HIDE_FOOTER, "badInputWarning");
+  }
+}
+
+function reportAssertionFailure(aMsg) {
+  let debug = Cc["@mozilla.org/xpcom/debug;1"].getService(Ci.nsIDebug2);
+  if (debug.isDebugBuild) {
+    debug.assertion(aMsg, "false", "aboutMemory.js", 0);
+  }
+}
+
+function debug(aVal) {
+  let section = appendElement(document.body, "div", "section");
+  appendElementWithText(section, "div", "debug", JSON.stringify(aVal));
+}
+
+function stringMatchesFilter(aString, aFilter) {
+  assert(
+    typeof aFilter == "string" || aFilter instanceof RegExp,
+    "unexpected aFilter type"
+  );
+
+  return typeof aFilter == "string"
+    ? aString.includes(aFilter)
+    : aFilter.test(aString);
+}
+
+// ---------------------------------------------------------------------------
+
+window.onunload = function () {};
+
+// ---------------------------------------------------------------------------
+
+// The <div> holding everything but the header and footer (if they're present).
+// It's what is updated each time the page changes.
+let gMain;
+
+// The <div> holding the footer.
+let gFooter;
+
+// The "verbose" checkbox.
+let gVerbose;
+
+// The "anonymize" checkbox.
+let gAnonymize;
+
+// Values for the |aFooterAction| argument to updateTitleMainAndFooter.
+const HIDE_FOOTER = 0;
+const SHOW_FOOTER = 1;
+
+// Values for the |aShowTimestamp| argument to updateTitleMainAndFooter.
+const NO_TIMESTAMP = 0;
+const SHOW_TIMESTAMP = 1;
+
+function updateTitleMainAndFooter(
+  aTitleNote,
+  aMsg,
+  aShowTimestamp,
+  aFooterAction,
+  aClassName
+) {
+  document.title = gPageName;
+  if (aTitleNote) {
+    document.title += ` (${aTitleNote})`;
+  }
+
+  // Clear gMain by replacing it with an empty node.
+  let tmp = gMain.cloneNode(false);
+  gMain.parentNode.replaceChild(tmp, gMain);
+  gMain = tmp;
+
+  gMain.classList.remove("hidden");
+  gMain.classList.remove("verbose");
+  gMain.classList.remove("non-verbose");
+  if (gVerbose) {
+    gMain.classList.add(gVerbose.checked ? "verbose" : "non-verbose");
+  }
+
+  let msgElement;
+  if (aMsg) {
+    let className = "section";
+    if (aClassName) {
+      className = className + " " + aClassName;
+    }
+    if (aShowTimestamp == SHOW_TIMESTAMP) {
+      // JS has many options for pretty-printing timestamps. We use
+      // toISOString() because it has sub-second granularity, which is useful
+      // if you quickly and repeatedly click one of the buttons.
+      aMsg += ` (${new Date().toISOString()})`;
+    }
+    msgElement = appendElementWithText(gMain, "div", className, aMsg);
+  }
+
+  switch (aFooterAction) {
+    case HIDE_FOOTER:
+      gFooter.classList.add("hidden");
+      break;
+    case SHOW_FOOTER:
+      gFooter.classList.remove("hidden");
+      break;
+    default:
+      assert(false, "bad footer action in updateTitleMainAndFooter");
+  }
+  return msgElement;
+}
+
+function updateMainAndFooter(aMsg, aShowTimestamp, aFooterAction, aClassName) {
+  return updateTitleMainAndFooter(
+    "",
+    aMsg,
+    aShowTimestamp,
+    aFooterAction,
+    aClassName
+  );
+}
+
+function appendTextNode(aP, aText) {
+  let e = document.createTextNode(aText);
+  aP.appendChild(e);
+  return e;
+}
+
+function appendElement(aP, aTagName, aClassName) {
+  let e = newElement(aTagName, aClassName);
+  aP.appendChild(e);
+  return e;
+}
+
+function appendElementWithText(aP, aTagName, aClassName, aText) {
+  let e = appendElement(aP, aTagName, aClassName);
+  // Setting textContent clobbers existing children, but there are none.  More
+  // importantly, it avoids creating a JS-land object for the node, saving
+  // memory.
+  e.textContent = aText;
+  return e;
+}
+
+function newElement(aTagName, aClassName) {
+  let e = document.createElement(aTagName);
+  if (aClassName) {
+    e.className = aClassName;
+  }
+  return e;
+}
+
+// ---------------------------------------------------------------------------
+
+const explicitTreeDescription =
+  "This tree covers explicit memory allocations by the application.  It includes \
+\n\n\
+* all allocations made at the heap allocation level (via functions such as malloc, \
+calloc, realloc, memalign, operator new, and operator new[]) that have not been \
+explicitly decommitted (i.e. evicted from memory and swap), and \
+\n\n\
+* some allocations (those covered by memory reporters) made at the operating \
+system level (via calls to functions such as VirtualAlloc, vm_allocate, and \
+mmap), \
+\n\n\
+* where possible, the overhead of the heap allocator itself.\
+\n\n\
+It excludes memory that is mapped implicitly such as code and data segments, \
+and thread stacks. \
+\n\n\
+'explicit' is not guaranteed to cover every explicit allocation, but it does cover \
+most (including the entire heap), and therefore it is the single best number to \
+focus on when trying to reduce memory usage.";
+
+// ---------------------------------------------------------------------------
+
+function appendButton(aP, aTitle, aOnClick, aText, aId) {
+  let b = appendElementWithText(aP, "button", "", aText);
+  b.title = aTitle;
+  b.onclick = aOnClick;
+  if (aId) {
+    b.id = aId;
+  }
+  return b;
+}
+
+function appendHiddenFileInput(aP, aId, aChangeListener) {
+  let input = appendElementWithText(aP, "input", "hidden", "");
+  input.type = "file";
+  input.id = aId; // used in testing
+  input.addEventListener("change", aChangeListener);
+  return input;
+}
+
+window.onload = function () {
+  // Generate the header.
+
+  let header = appendElement(document.body, "div", "ancillary");
+
+  // A hidden file input element that can be invoked when necessary.
+  let fileInput1 = appendHiddenFileInput(header, "fileInput1", function () {
+    let file = this.files[0];
+    let filename = file.mozFullPath;
+    updateAboutMemoryFromFile(filename);
+  });
+
+  // Ditto.
+  let fileInput2 = appendHiddenFileInput(
+    header,
+    "fileInput2",
+    function (aElem) {
+      let file = this.files[0];
+      // First time around, we stash a copy of the filename and reinvoke.  Second
+      // time around we do the diff and display.
+      if (!this.filename1) {
+        this.filename1 = file.mozFullPath;
+
+        // aElem.skipClick is only true when testing -- it allows fileInput2's
+        // onchange handler to be re-called without having to go via the file
+        // picker.
+        if (!aElem.skipClick) {
+          this.click();
+        }
+      } else {
+        let filename1 = this.filename1;
+        delete this.filename1;
+        updateAboutMemoryFromTwoFiles(filename1, file.mozFullPath);
+      }
+    }
+  );
+
+  const CuDesc = "Measure current memory reports and show.";
+  const LdDesc = "Load memory reports from file and show.";
+  const DfDesc =
+    "Load memory report data from two files and show the difference.";
+
+  const SvDesc = "Save memory reports to file.";
+
+  const GCDesc = "Do a global garbage collection.";
+  const CCDesc = "Do a cycle collection.";
+  const MMDesc =
+    'Send three "heap-minimize" notifications in a ' +
+    "row.  Each notification triggers a global garbage " +
+    "collection followed by a cycle collection, and causes the " +
+    "process to reduce memory usage in other ways, e.g. by " +
+    "flushing various caches.";
+
+  const GCAndCCLogDesc =
+    "Save garbage collection log and concise cycle " +
+    "collection log.\n" +
+    "WARNING: These logs may be large (>1GB).";
+  const GCAndCCAllLogDesc =
+    "Save garbage collection log and verbose cycle " +
+    "collection log.\n" +
+    "WARNING: These logs may be large (>1GB).";
+
+  const DMDEnabledDesc =
+    "Analyze memory reports coverage and save the " +
+    "output to the temp directory.\n";
+  const DMDDisabledDesc =
+    "DMD is not running. Please re-start with $DMD and " +
+    "the other relevant environment variables set " +
+    "appropriately.";
+
+  let ops = appendElement(header, "div", "");
+
+  let row1 = appendElement(ops, "div", "opsRow");
+
+  let labelDiv1 = appendElementWithText(
+    row1,
+    "div",
+    "opsRowLabel",
+    "Show memory reports"
+  );
+  labelDiv1.setAttribute("role", "heading");
+  labelDiv1.setAttribute("aria-level", "1");
+  let label1 = appendElementWithText(labelDiv1, "label", "");
+  gVerbose = appendElement(label1, "input", "");
+  gVerbose.type = "checkbox";
+  gVerbose.id = "verbose"; // used for testing
+  appendTextNode(label1, "verbose");
+
+  // The "measureButton" id is used for testing.
+  appendButton(row1, CuDesc, doMeasure, "Measure", "measureButton");
+  appendButton(row1, LdDesc, () => fileInput1.click(), "Load…");
+  appendButton(row1, DfDesc, () => fileInput2.click(), "Load and diff…");
+
+  let row2 = appendElement(ops, "div", "opsRow");
+
+  let labelDiv2 = appendElementWithText(
+    row2,
+    "div",
+    "opsRowLabel",
+    "Save memory reports"
+  );
+  labelDiv2.setAttribute("role", "heading");
+  labelDiv2.setAttribute("aria-level", "1");
+  appendButton(row2, SvDesc, saveReportsToFile, "Measure and save…");
+
+  // XXX: this isn't a great place for this checkbox, but I can't think of
+  // anywhere better.
+  let label2 = appendElementWithText(labelDiv2, "label", "");
+  gAnonymize = appendElement(label2, "input", "");
+  gAnonymize.type = "checkbox";
+  appendTextNode(label2, "anonymize");
+
+  let row3 = appendElement(ops, "div", "opsRow");
+
+  let labelDiv3 = appendElementWithText(
+    row3,
+    "div",
+    "opsRowLabel",
+    "Free memory"
+  );
+  labelDiv3.setAttribute("role", "heading");
+  labelDiv3.setAttribute("aria-level", "1");
+  appendButton(row3, GCDesc, doGC, "GC");
+  appendButton(row3, CCDesc, doCC, "CC");
+  appendButton(row3, MMDesc, doMMU, "Minimize memory usage");
+
+  let row4 = appendElement(ops, "div", "opsRow");
+
+  let labelDiv4 = appendElementWithText(
+    row4,
+    "div",
+    "opsRowLabel",
+    "Save GC & CC logs"
+  );
+  labelDiv4.setAttribute("role", "heading");
+  labelDiv4.setAttribute("aria-level", "1");
+  appendButton(
+    row4,
+    GCAndCCLogDesc,
+    saveGCLogAndConciseCCLog,
+    "Save concise",
+    "saveLogsConcise"
+  );
+  appendButton(
+    row4,
+    GCAndCCAllLogDesc,
+    saveGCLogAndVerboseCCLog,
+    "Save verbose",
+    "saveLogsVerbose"
+  );
+
+  // Three cases here:
+  // - DMD is disabled (i.e. not built): don't show the button.
+  // - DMD is enabled but is not running: show the button, but disable it.
+  // - DMD is enabled and is running: show the button and enable it.
+  if (gMgr.isDMDEnabled) {
+    let row5 = appendElement(ops, "div", "opsRow");
+
+    let labelDiv5 = appendElementWithText(
+      row5,
+      "div",
+      "opsRowLabel",
+      "Save DMD output"
+    );
+    labelDiv5.setAttribute("role", "heading");
+    labelDiv5.setAttribute("aria-level", "1");
+    let enableButtons = gMgr.isDMDRunning;
+
+    let dmdButton = appendButton(
+      row5,
+      enableButtons ? DMDEnabledDesc : DMDDisabledDesc,
+      doDMD,
+      "Save"
+    );
+    dmdButton.disabled = !enableButtons;
+  }
+
+  // Generate the main div, where content ("section" divs) will go.  It's
+  // hidden at first.
+
+  gMain = appendElement(document.body, "div", "");
+  gMain.id = "mainDiv";
+
+  // Generate the footer.  It's hidden at first.
+
+  gFooter = appendElement(document.body, "div", "ancillary hidden");
+  gFooter.setAttribute("role", "contentinfo");
+
+  if (Services.policies.isAllowed("aboutSupport")) {
+    let a = appendElementWithText(
+      gFooter,
+      "a",
+      "option",
+      "Troubleshooting information"
+    );
+    a.href = "about:support";
+  }
+
+  let legendText1 =
+    "Click on a non-leaf node in a tree to expand ('++') " +
+    "or collapse ('--') its children.";
+  let legendText2 =
+    "Hover the pointer over the name of a memory report " +
+    "to see a description of what it measures.";
+
+  appendElementWithText(gFooter, "div", "legend", legendText1);
+  appendElementWithText(gFooter, "div", "legend hiddenOnMobile", legendText2);
+
+  // See if we're loading from a file.  (Because about:memory is a non-standard
+  // URL, location.search is undefined, so we have to use location.href
+  // instead.)
+  let search = location.href.split("?")[1];
+  if (search) {
+    let searchSplit = search.split("&");
+    for (let s of searchSplit) {
+      if (s.toLowerCase().startsWith("file=")) {
+        let filename = s.substring("file=".length);
+        updateAboutMemoryFromFile(decodeURIComponent(filename));
+        return;
+      }
+    }
+  }
+};
+
+// ---------------------------------------------------------------------------
+
+function doGC() {
+  Services.obs.notifyObservers(null, "child-gc-request");
+  Cu.forceGC();
+  updateMainAndFooter(
+    "Garbage collection completed",
+    SHOW_TIMESTAMP,
+    HIDE_FOOTER
+  );
+}
+
+function doCC() {
+  Services.obs.notifyObservers(null, "child-cc-request");
+  window.windowUtils.cycleCollect();
+  updateMainAndFooter(
+    "Cycle collection completed",
+    SHOW_TIMESTAMP,
+    HIDE_FOOTER
+  );
+}
+
+function doMMU() {
+  Services.obs.notifyObservers(null, "child-mmu-request");
+  gMgr.minimizeMemoryUsage(() =>
+    updateMainAndFooter(
+      "Memory minimization completed",
+      SHOW_TIMESTAMP,
+      HIDE_FOOTER
+    )
+  );
+}
+
+function doMeasure() {
+  updateAboutMemoryFromReporters();
+}
+
+function saveGCLogAndConciseCCLog() {
+  dumpGCLogAndCCLog(false);
+}
+
+function saveGCLogAndVerboseCCLog() {
+  dumpGCLogAndCCLog(true);
+}
+
+function doDMD() {
+  updateMainAndFooter(
+    "Saving memory reports and DMD output...",
+    NO_TIMESTAMP,
+    HIDE_FOOTER
+  );
+  try {
+    let dumper = Cc["@mozilla.org/memory-info-dumper;1"].getService(
+      Ci.nsIMemoryInfoDumper
+    );
+
+    dumper.dumpMemoryInfoToTempDir(
+      /* identifier = */ "",
+      gAnonymize.checked,
+      /* minimize = */ false
+    );
+    updateMainAndFooter(
+      "Saved memory reports and DMD reports analysis " +
+        "to the temp directory",
+      SHOW_TIMESTAMP,
+      HIDE_FOOTER
+    );
+  } catch (ex) {
+    updateMainAndFooter(ex.toString(), NO_TIMESTAMP, HIDE_FOOTER);
+  }
+}
+
+function dumpGCLogAndCCLog(aVerbose) {
+  let dumper = Cc["@mozilla.org/memory-info-dumper;1"].getService(
+    Ci.nsIMemoryInfoDumper
+  );
+
+  let inProgress = updateMainAndFooter(
+    "Saving logs...",
+    NO_TIMESTAMP,
+    HIDE_FOOTER
+  );
+  let section = appendElement(gMain, "div", "section");
+
+  function displayInfo(aGCLog, aCCLog, aIsParent) {
+    appendElementWithText(section, "div", "", "Saved GC log to " + aGCLog.path);
+
+    let ccLogType = aVerbose ? "verbose" : "concise";
+    appendElementWithText(
+      section,
+      "div",
+      "",
+      "Saved " + ccLogType + " CC log to " + aCCLog.path
+    );
+  }
+
+  dumper.dumpGCAndCCLogsToFile("", aVerbose, /* dumpChildProcesses = */ true, {
+    onDump: displayInfo,
+    onFinish() {
+      inProgress.remove();
+    },
+  });
+}
+
+/**
+ * Top-level function that does the work of generating the page from the memory
+ * reporters.
+ */
+function updateAboutMemoryFromReporters() {
+  updateMainAndFooter("Measuring...", NO_TIMESTAMP, HIDE_FOOTER);
+
+  try {
+    gCurrentReports = [];
+    gCurrentHasMozMallocUsableSize = gMgr.hasMozMallocUsableSize;
+    gCurrentIsDiff = false;
+    gFilter = "";
+
+    // Record the reports from the live memory reporters then process them.
+    let handleReport = function (
+      aProcess,
+      aUnsafePath,
+      aKind,
+      aUnits,
+      aAmount,
+      aDescription
+    ) {
+      gCurrentReports.push({
+        process: aProcess,
+        path: aUnsafePath,
+        kind: aKind,
+        units: aUnits,
+        amount: aAmount,
+        description: aDescription,
+      });
+    };
+
+    let displayReports = function () {
+      updateTitleMainAndFooter(
+        "live measurement",
+        "",
+        NO_TIMESTAMP,
+        SHOW_FOOTER
+      );
+      updateAboutMemoryFromCurrentData();
+    };
+
+    gMgr.getReports(
+      handleReport,
+      null,
+      displayReports,
+      null,
+      gAnonymize.checked
+    );
+  } catch (ex) {
+    handleException(ex);
+  }
+}
+
+// Increment this if the JSON format changes.
+//
+let gCurrentFileFormatVersion = 1;
+
+/**
+ * Parse a string as JSON and extract the |memory_report| property if it has
+ * one, which indicates the string is from a crash dump.
+ *
+ * @param aStr
+ *        The string.
+ * @return The extracted object.
+ */
+function parseAndUnwrapIfCrashDump(aStr) {
+  let obj = JSON.parse(aStr);
+  if (obj.memory_report !== undefined) {
+    // It looks like a crash dump. The memory reports should be in the
+    // |memory_report| property.
+    obj = obj.memory_report;
+  }
+  return obj;
+}
+
+/**
+ * Populate about:memory using the data stored in gCurrentReports and
+ * gCurrentHasMozMallocUsableSize.
+ */
+function updateAboutMemoryFromCurrentData() {
+  function processCurrentMemoryReports(aHandleReport, aDisplayReports) {
+    for (let r of gCurrentReports) {
+      aHandleReport(
+        r.process,
+        r.path,
+        r.kind,
+        r.units,
+        r.amount,
+        r.description,
+        r._presence
+      );
+    }
+    aDisplayReports();
+  }
+
+  gIsDiff = gCurrentIsDiff;
+  appendAboutMemoryMain(
+    processCurrentMemoryReports,
+    gFilter,
+    gCurrentHasMozMallocUsableSize
+  );
+  gIsDiff = false;
+}
+
+/**
+ * Populate about:memory using the data in the given JSON object.
+ *
+ * @param aObj
+ *        An object that (hopefully!) conforms to the JSON schema used by
+ *        nsIMemoryInfoDumper.
+ */
+function updateAboutMemoryFromJSONObject(aObj) {
+  try {
+    assertInput(
+      aObj.version === gCurrentFileFormatVersion,
+      "data version number missing or doesn't match"
+    );
+    assertInput(
+      aObj.hasMozMallocUsableSize !== undefined,
+      "missing 'hasMozMallocUsableSize' property"
+    );
+    assertInput(
+      aObj.reports && aObj.reports instanceof Array,
+      "missing or non-array 'reports' property"
+    );
+
+    gCurrentReports = aObj.reports.concat();
+    gCurrentHasMozMallocUsableSize = aObj.hasMozMallocUsableSize;
+    gCurrentIsDiff = gIsDiff;
+    gFilter = "";
+
+    updateAboutMemoryFromCurrentData();
+  } catch (ex) {
+    handleException(ex);
+  }
+}
+
+/**
+ * Populate about:memory using the data in the given JSON string.
+ *
+ * @param aStr
+ *        A string containing JSON data conforming to the schema used by
+ *        nsIMemoryReporterManager::dumpReports.
+ */
+function updateAboutMemoryFromJSONString(aStr) {
+  try {
+    let obj = parseAndUnwrapIfCrashDump(aStr);
+    updateAboutMemoryFromJSONObject(obj);
+  } catch (ex) {
+    handleException(ex);
+  }
+}
+
+/**
+ * Loads the contents of a file into a string and passes that to a callback.
+ *
+ * @param aFilename
+ *        The name of the file being read from.
+ * @param aTitleNote
+ *        A description to put in the page title upon completion.
+ * @param aFn
+ *        The function to call and pass the read string to upon completion.
+ */
+function loadMemoryReportsFromFile(aFilename, aTitleNote, aFn) {
+  updateMainAndFooter("Loading...", NO_TIMESTAMP, HIDE_FOOTER);
+
+  try {
+    let reader = new FileReader();
+    reader.onerror = () => {
+      throw new Error("FileReader.onerror");
+    };
+    reader.onabort = () => {
+      throw new Error("FileReader.onabort");
+    };
+    reader.onload = aEvent => {
+      // Clear "Loading..." from above.
+      updateTitleMainAndFooter(aTitleNote, "", NO_TIMESTAMP, SHOW_FOOTER);
+      aFn(aEvent.target.result);
+    };
+
+    // If it doesn't have a .gz suffix, read it as a (legacy) ungzipped file.
+    if (!aFilename.endsWith(".gz")) {
+      File.createFromFileName(aFilename).then(file => {
+        reader.readAsText(file);
+      });
+      return;
+    }
+
+    // Read compressed gzip file.
+    let converter = new nsGzipConverter();
+    converter.asyncConvertData(
+      "gzip",
+      "uncompressed",
+      {
+        data: [],
+        onStartRequest(aR, aC) {},
+        onDataAvailable(aR, aStream, aO, aCount) {
+          let bi = new nsBinaryStream(aStream);
+          this.data.push(bi.readBytes(aCount));
+        },
+        onStopRequest(aR, aC, aStatusCode) {
+          try {
+            if (!Components.isSuccessCode(aStatusCode)) {
+              throw new Components.Exception(
+                "Error while reading gzip file",
+                aStatusCode
+              );
+            }
+            reader.readAsText(new Blob(this.data));
+          } catch (ex) {
+            handleException(ex);
+          }
+        },
+      },
+      null
+    );
+
+    let file = new nsFile(aFilename);
+    let fileChan = NetUtil.newChannel({
+      uri: Services.io.newFileURI(file),
+      loadUsingSystemPrincipal: true,
+    });
+    fileChan.asyncOpen(converter);
+  } catch (ex) {
+    handleException(ex);
+  }
+}
+
+/**
+ * Like updateAboutMemoryFromReporters(), but gets its data from a file instead
+ * of the memory reporters.
+ *
+ * @param aFilename
+ *        The name of the file being read from.  The expected format of the
+ *        file's contents is described in a comment in nsIMemoryInfoDumper.idl.
+ */
+function updateAboutMemoryFromFile(aFilename) {
+  loadMemoryReportsFromFile(
+    aFilename,
+    /* title note */ aFilename,
+    updateAboutMemoryFromJSONString
+  );
+}
+
+/**
+ * Like updateAboutMemoryFromFile(), but gets its data from a two files and
+ * diffs them.
+ *
+ * @param aFilename1
+ *        The name of the first file being read from.
+ * @param aFilename2
+ *        The name of the first file being read from.
+ */
+function updateAboutMemoryFromTwoFiles(aFilename1, aFilename2) {
+  let titleNote = `diff of ${aFilename1} and ${aFilename2}`;
+  loadMemoryReportsFromFile(aFilename1, titleNote, function (aStr1) {
+    loadMemoryReportsFromFile(aFilename2, titleNote, function (aStr2) {
+      try {
+        let obj1 = parseAndUnwrapIfCrashDump(aStr1);
+        let obj2 = parseAndUnwrapIfCrashDump(aStr2);
+        gIsDiff = true;
+        updateAboutMemoryFromJSONObject(diffJSONObjects(obj1, obj2));
+        gIsDiff = false;
+      } catch (ex) {
+        handleException(ex);
+      }
+    });
+  });
+}
+
+// ---------------------------------------------------------------------------
+
+// Something unlikely to appear in a process name.
+let kProcessPathSep = "^:^:^";
+
+// Short for "diff report".
+function DReport(aKind, aUnits, aAmount, aDescription, aNMerged, aPresence) {
+  this._kind = aKind;
+  this._units = aUnits;
+  this._amount = aAmount;
+  this._description = aDescription;
+  this._nMerged = aNMerged;
+  if (aPresence !== undefined) {
+    this._presence = aPresence;
+  }
+}
+
+DReport.prototype = {
+  assertCompatible(aKind, aUnits) {
+    assert(this._kind == aKind, "Mismatched kinds");
+    assert(this._units == aUnits, "Mismatched units");
+
+    // We don't check that the "description" properties match.  This is because
+    // on Linux we can get cases where the paths are the same but the
+    // descriptions differ, like this:
+    //
+    //   "path": "size/other-files/icon-theme.cache/[r--p]",
+    //   "description": "/usr/share/icons/gnome/icon-theme.cache (read-only, not executable, private)"
+    //
+    //   "path": "size/other-files/icon-theme.cache/[r--p]"
+    //   "description": "/usr/share/icons/hicolor/icon-theme.cache (read-only, not executable, private)"
+    //
+    // In those cases, we just use the description from the first-encountered
+    // one, which is what about:memory also does.
+    // (Note: reports with those paths are no longer generated, but allowing
+    // the descriptions to differ seems reasonable.)
+  },
+
+  merge(aJr) {
+    this.assertCompatible(aJr.kind, aJr.units);
+    this._amount += aJr.amount;
+    this._nMerged++;
+  },
+
+  toJSON(aProcess, aPath, aAmount) {
+    return {
+      process: aProcess,
+      path: aPath,
+      kind: this._kind,
+      units: this._units,
+      amount: aAmount,
+      description: this._description,
+      _presence: this._presence,
+    };
+  },
+};
+
+// Constants that indicate if a DReport was present only in one of the data
+// sets, or had to be added for balance.
+DReport.PRESENT_IN_FIRST_ONLY = 1;
+DReport.PRESENT_IN_SECOND_ONLY = 2;
+DReport.ADDED_FOR_BALANCE = 3;
+
+/**
+ * Return true if the report contains a webIsolated process,
+ * which is a good indication that Fission is enabled.
+ */
+function hasWebIsolatedProcess(aJSONReports) {
+  for (let jr of aJSONReports) {
+    assert(jr.process !== undefined, "Missing process");
+    if (jr.process.startsWith("webIsolated")) {
+      return true;
+    }
+  }
+  return false;
+}
+
+/**
+ * Make a report map, which has combined path+process strings for keys, and
+ * DReport objects for values.
+ *
+ * @param aJSONReports
+ *        The |reports| field of a JSON object.
+ * @param aForgetIsolation
+          If this is true, treat webIsolated processes like web processes.
+ * @return The constructed report map.
+ */
+function makeDReportMap(aJSONReports, aForgetIsolation) {
+  let dreportMap = {};
+  for (let jr of aJSONReports) {
+    assert(jr.process !== undefined, "Missing process");
+    assert(jr.path !== undefined, "Missing path");
+    assert(jr.kind !== undefined, "Missing kind");
+    assert(jr.units !== undefined, "Missing units");
+    assert(jr.amount !== undefined, "Missing amount");
+    assert(jr.description !== undefined, "Missing description");
+
+    // Strip out some non-deterministic stuff that prevents clean diffs.
+    // Ideally the memory reports themselves would contain information about
+    // which parts of the the process and path need to be stripped -- saving us
+    // from hardwiring knowledge of specific reporters here -- but we have no
+    // mechanism for that. (Any future redesign of how memory reporters work
+    // should include such a mechanism.)
+
+    // Strip PIDs:
+    // - pid 123
+    // - pid=123
+    // - pid: 123
+    let pidRegex = /pid([ =]|: )\d+/g;
+    let pidSubst = "pid$1NNN";
+    let process = jr.process.replace(pidRegex, pidSubst);
+    let path = jr.path.replace(pidRegex, pidSubst);
+
+    if (aForgetIsolation && process.startsWith("webIsolated")) {
+      process = "web (pid NNN)";
+    }
+
+    // Strip TIDs and threadpool IDs.
+    path = path.replace(/\(tid=(\d+)\)/, "(tid=NNN)");
+    path = path.replace(/#\d+ \(tid=NNN\)/, "#N (tid=NNN)");
+
+    // Strip addresses:
+    // - .../js-zone(0x12345678)/...
+    // - .../zone(0x12345678)/...
+    // - .../worker(<URL>, 0x12345678)/...
+    path = path.replace(/zone\(0x[0-9A-Fa-f]+\)\//, "zone(0xNNN)/");
+    path = path.replace(
+      /\/worker\((.+), 0x[0-9A-Fa-f]+\)\//,
+      "/worker($1, 0xNNN)/"
+    );
+
+    // Strip top window IDs:
+    // - explicit/window-objects/top(<URL>, id=123)/...
+    // - event-counts/window-objects/top(<URL>, id=123)/...
+    path = path.replace(
+      /^((?:explicit|event-counts)\/window-objects\/top\(.*, id=)\d+\)/,
+      "$1NNN)"
+    );
+
+    // Strip null principal UUIDs (but not other UUIDs, because they may be
+    // deterministic, such as those used by add-ons).
+    path = path.replace(
+      /moz-nullprincipal:{........-....-....-....-............}/g,
+      "moz-nullprincipal:{NNNNNNNN-NNNN-NNNN-NNNN-NNNNNNNNNNNN}"
+    );
+
+    // Strip segment counts from address-space.
+    if (path.startsWith("address-space")) {
+      path = path.replace(/\(segments=\d+\)/g, "(segments=NNNN)");
+    }
+
+    // Normalize omni.ja! paths.
+    path = path.replace(
+      /jar:file:\\\\\\(.+)\\omni.ja!/,
+      "jar:file:\\\\\\...\\omni.ja!"
+    );
+
+    // Normalize script source counts.
+    path = path.replace(/source\(scripts=(\d+), /, "source(scripts=NNN, ");
+
+    let processPath = process + kProcessPathSep + path;
+    let rOld = dreportMap[processPath];
+    if (rOld === undefined) {
+      dreportMap[processPath] = new DReport(
+        jr.kind,
+        jr.units,
+        jr.amount,
+        jr.description,
+        1,
+        undefined
+      );
+    } else {
+      rOld.merge(jr);
+    }
+  }
+  return dreportMap;
+}
+
+// Return a new dreportMap which is the diff of two dreportMaps.  Empties
+// aDReportMap2 along the way.
+function diffDReportMaps(aDReportMap1, aDReportMap2) {
+  let result = {};
+
+  for (let processPath in aDReportMap1) {
+    let r1 = aDReportMap1[processPath];
+    let r2 = aDReportMap2[processPath];
+    let r2_amount, r2_nMerged;
+    let presence;
+    if (r2 !== undefined) {
+      r1.assertCompatible(r2._kind, r2._units);
+      r2_amount = r2._amount;
+      r2_nMerged = r2._nMerged;
+      delete aDReportMap2[processPath];
+      presence = undefined; // represents that it's present in both
+    } else {
+      r2_amount = 0;
+      r2_nMerged = 0;
+      presence = DReport.PRESENT_IN_FIRST_ONLY;
+    }
+    result[processPath] = new DReport(
+      r1._kind,
+      r1._units,
+      r2_amount - r1._amount,
+      r1._description,
+      Math.max(r1._nMerged, r2_nMerged),
+      presence
+    );
+  }
+
+  for (let processPath in aDReportMap2) {
+    let r2 = aDReportMap2[processPath];
+    result[processPath] = new DReport(
+      r2._kind,
+      r2._units,
+      r2._amount,
+      r2._description,
+      r2._nMerged,
+      DReport.PRESENT_IN_SECOND_ONLY
+    );
+  }
+
+  return result;
+}
+
+function makeJSONReports(aDReportMap) {
+  let reports = [];
+  for (let processPath in aDReportMap) {
+    let r = aDReportMap[processPath];
+    if (r._amount !== 0) {
+      // If _nMerged > 1, we give the full (aggregated) amount in the first
+      // copy, and then use amount=0 in the remainder.  When viewed in
+      // about:memory, this shows up as an entry with a "[2]"-style suffix
+      // and the correct amount.
+      let split = processPath.split(kProcessPathSep);
+      assert(split.length >= 2);
+      let process = split.shift();
+      let path = split.join();
+      reports.push(r.toJSON(process, path, r._amount));
+      for (let i = 1; i < r._nMerged; i++) {
+        reports.push(r.toJSON(process, path, 0));
+      }
+    }
+  }
+
+  return reports;
+}
+
+// Diff two JSON objects holding memory reports.
+function diffJSONObjects(aJson1, aJson2) {
+  function simpleProp(aProp) {
+    assert(
+      aJson1[aProp] !== undefined && aJson1[aProp] === aJson2[aProp],
+      aProp + " properties don't match"
+    );
+    return aJson1[aProp];
+  }
+
+  // If one report we're diffing contains webIsolated processes, but the other
+  // does not, then we're probably comparing a report with Fission enabled with
+  // one where it is not enabled. In this case, we want to make all of the
+  // webIsolated processes look like plain old web processes to get a better
+  // diff.
+  let hasIsolated1 = hasWebIsolatedProcess(aJson1.reports);
+  let hasIsolated2 = hasWebIsolatedProcess(aJson2.reports);
+  let eitherIsolated = hasIsolated1 || hasIsolated2;
+  let forgetIsolation = hasIsolated1 != hasIsolated2 && eitherIsolated;
+
+  return {
+    version: simpleProp("version"),
+
+    hasMozMallocUsableSize: simpleProp("hasMozMallocUsableSize"),
+
+    reports: makeJSONReports(
+      diffDReportMaps(
+        makeDReportMap(aJson1.reports, forgetIsolation),
+        makeDReportMap(aJson2.reports, forgetIsolation)
+      )
+    ),
+  };
+}
+
+// ---------------------------------------------------------------------------
+
+// |PColl| is short for "process collection".
+function PColl() {
+  this._trees = {};
+  this._degenerates = {};
+  this._heapTotal = 0;
+}
+
+/**
+ * Processes reports (whether from reporters or from a file) and append the
+ * main part of the page.
+ *
+ * @param aProcessReports
+ *        Function that extracts the memory reports from the reporters or from
+ *        file.
+ * @param aFilter
+ *        String or RegExp used to filter reports by their path.
+ * @param aHasMozMallocUsableSize
+ *        Boolean indicating if moz_malloc_usable_size works.
+ */
+function appendAboutMemoryMain(
+  aProcessReports,
+  aFilter,
+  aHasMozMallocUsableSize
+) {
+  let pcollsByProcess = {};
+  let infoByProcess = {};
+
+  function handleReport(
+    aProcess,
+    aUnsafePath,
+    aKind,
+    aUnits,
+    aAmount,
+    aDescription,
+    aPresence
+  ) {
+    if (aUnsafePath.startsWith("explicit/")) {
+      assertInput(
+        aKind === KIND_HEAP || aKind === KIND_NONHEAP,
+        "bad explicit kind"
+      );
+      assertInput(aUnits === UNITS_BYTES, "bad explicit units");
+    }
+
+    assert(
+      aPresence === undefined ||
+        aPresence == DReport.PRESENT_IN_FIRST_ONLY ||
+        aPresence == DReport.PRESENT_IN_SECOND_ONLY,
+      "bad presence"
+    );
+
+    // If the process is empty, that means this process -- which is the main
+    // process, because this is chrome JS code -- is doing the dumping.
+    // Generate the process identifier: `Main Process (pid $PID)`.
+    //
+    // Note that `HandleReportAndFinishReportingCallbacks::Callback()` handles
+    // this when saving memory reports to file. So, if we are loading memory
+    // reports from file then `aProcess` will already be non-empty.
+    let process = aProcess
+      ? aProcess
+      : gMainProcessPrefix + " (pid " + Services.appinfo.processID + ")";
+
+    // Store the "resident" value for each process, so that if we filter it
+    // out, we can still use it to correctly sort processes and generate the
+    // process index.
+    let info = infoByProcess[process];
+    if (!info) {
+      info = infoByProcess[process] = {};
+    }
+    if (aUnsafePath == "resident") {
+      infoByProcess[process].resident = aAmount;
+    }
+
+    // Ignore reports that don't match the current filter.
+    if (!stringMatchesFilter(aUnsafePath, aFilter)) {
+      return;
+    }
+
+    let unsafeNames = aUnsafePath.split("/");
+    let unsafeName0 = unsafeNames[0];
+    let isDegenerate = unsafeNames.length === 1;
+
+    // Get the PColl table for the process, creating it if necessary.
+    let pcoll = pcollsByProcess[process];
+    if (!pcollsByProcess[process]) {
+      pcoll = pcollsByProcess[process] = new PColl();
+    }
+
+    // Get the root node, creating it if necessary.
+    let psubcoll = isDegenerate ? pcoll._degenerates : pcoll._trees;
+    let t = psubcoll[unsafeName0];
+    if (!t) {
+      t = psubcoll[unsafeName0] = new TreeNode(
+        unsafeName0,
+        aUnits,
+        isDegenerate
+      );
+    }
+
+    if (!isDegenerate) {
+      // Add any missing nodes in the tree implied by aUnsafePath, and fill in
+      // the properties that we can with a top-down traversal.
+      for (let i = 1; i < unsafeNames.length; i++) {
+        let unsafeName = unsafeNames[i];
+        let u = t.findKid(unsafeName);
+        if (!u) {
+          u = new TreeNode(unsafeName, aUnits, isDegenerate);
+          if (!t._kids) {
+            t._kids = [];
+          }
+          t._kids.push(u);
+        }
+        t = u;
+      }
+
+      // Update the heap total if necessary.
+      if (unsafeName0 === "explicit" && aKind == KIND_HEAP) {
+        pcollsByProcess[process]._heapTotal += aAmount;
+      }
+    }
+
+    if (t._amount) {
+      // Duplicate!  Sum the values and mark it as a dup.
+      t._amount += aAmount;
+      t._nMerged = t._nMerged ? t._nMerged + 1 : 2;
+      assert(t._presence === aPresence, "presence mismatch");
+    } else {
+      // New leaf node.  Fill in extra node details from the report.
+      t._amount = aAmount;
+      t._description = aDescription;
+      if (aPresence !== undefined) {
+        t._presence = aPresence;
+      }
+    }
+  }
+
+  function displayReports() {
+    // Sort the processes.
+    let processes = Object.keys(infoByProcess);
+    processes.sort(function (aProcessA, aProcessB) {
+      assert(
+        aProcessA != aProcessB,
+        `Elements of Object.keys() should be unique, but ` +
+          `saw duplicate '${aProcessA}' elem.`
+      );
+
+      // Always put the main process first.
+      if (aProcessA.startsWith(gMainProcessPrefix)) {
+        return -1;
+      }
+      if (aProcessB.startsWith(gMainProcessPrefix)) {
+        return 1;
+      }
+
+      // Then sort by resident size.
+      let residentA = infoByProcess[aProcessA].resident || -1;
+      let residentB = infoByProcess[aProcessB].resident || -1;
+      if (residentA > residentB) {
+        return -1;
+      }
+      if (residentA < residentB) {
+        return 1;
+      }
+
+      // Then sort by process name.
+      if (aProcessA < aProcessB) {
+        return -1;
+      }
+      if (aProcessA > aProcessB) {
+        return 1;
+      }
+
+      return 0;
+    });
+
+    // We set up this general layout inside gMain:
+    //
+    //   <div class="outputContainer">
+    //     <div class="sections"></div>
+    //     <div class="sidebar">
+    //       <div class="sidebarContents">
+    //         <div class="sidebarItem filterItem"></div>
+    //         <div class="sidebarItem indexItem"></div>
+    //       </div>
+    //     </div>
+    //   </div>
+    //
+    // If we detect that outputContainer already exists, then this is an update
+    // (due to typing in a filter string) to an already-displayed memory report.
+    // In this case we preserve the structure of the layout and only replace
+    // div.sections and #indexItem. Preserving the filter sidebar item means we
+    // preserve any editing state in its <input>.
+
+    // Generate the main process sections.
+    let sections = newElement("div", "sections");
+    sections.setAttribute("role", "main");
+
+    for (let [i, process] of processes.entries()) {
+      let pcolls = pcollsByProcess[process];
+      if (!pcolls) {
+        continue;
+      }
+
+      let section = appendElement(sections, "div", "section");
+      appendProcessAboutMemoryElements(
+        section,
+        i,
+        process,
+        pcolls._trees,
+        pcolls._degenerates,
+        pcolls._heapTotal,
+        aHasMozMallocUsableSize,
+        aFilter != ""
+      );
+    }
+
+    if (!sections.firstChild) {
+      appendElementWithText(sections, "div", "section", "No results found.");
+    }
+
+    // Generate the process index.
+    let indexItem = newElement("div", "sidebarItem");
+    indexItem.classList.add("indexItem");
+    appendElementWithText(indexItem, "div", "sidebarLabel", "Process index");
+    let indexList = appendElement(indexItem, "ul", "index");
+
+    for (let [i, process] of processes.entries()) {
+      let indexListItem = appendElement(indexList, "li");
+      let pcolls = pcollsByProcess[process];
+      if (pcolls) {
+        let indexLink = appendElementWithText(indexListItem, "a", "", process);
+        indexLink.href = "#start" + i;
+      } else {
+        // We've filtered out all reports from this process. Generate a non-link
+        // entry in the process index, and skip creating a process report
+        // section.
+        indexListItem.textContent = process;
+      }
+    }
+
+    // If we are updating, just swap in the new process output.
+    let outputContainer = gMain.querySelector(".outputContainer");
+    if (outputContainer) {
+      outputContainer.querySelector(".sections").replaceWith(sections);
+      outputContainer.querySelector(".indexItem").replaceWith(indexItem);
+      return;
+    }
+
+    // Otherwise, generate the rest of the layout.
+    outputContainer = appendElement(gMain, "div", "outputContainer");
+    outputContainer.appendChild(sections);
+
+    let sidebar = appendElement(outputContainer, "div", "sidebar");
+    sidebar.setAttribute("role", "navigation");
+    let sidebarContents = appendElement(sidebar, "div", "sidebarContents");
+
+    // Generate the filter input and checkbox.
+    let filterItem = appendElement(sidebarContents, "div", "sidebarItem");
+    filterItem.classList.add("filterItem");
+    appendElementWithText(filterItem, "div", "sidebarLabel", "Filter");
+
+    let filterInput = appendElement(filterItem, "input", "filterInput");
+    filterInput.placeholder = "Memory report path filter";
+
+    let filterOptions = appendElement(filterItem, "div");
+    let filterRegExLabel = appendElement(filterOptions, "label");
+    let filterRegExCheckbox = appendElement(filterRegExLabel, "input");
+    filterRegExCheckbox.type = "checkbox";
+    filterRegExLabel.append(" Regular expression");
+
+    // Set up event handlers to update the display if the filter input or
+    // checkbox changes.
+    let filterUpdateTimeout;
+    let filterUpdate = function () {
+      if (filterUpdateTimeout) {
+        window.clearTimeout(filterUpdateTimeout);
+      }
+      filterUpdateTimeout = window.setTimeout(function () {
+        try {
+          gFilter =
+            filterRegExCheckbox.checked && filterInput.value != ""
+              ? new RegExp(filterInput.value)
+              : filterInput.value;
+        } catch (ex) {
+          // Match nothing if the regex was invalid.
+          gFilter = new RegExp("^$");
+        }
+        updateAboutMemoryFromCurrentData();
+      }, gFilterUpdateDelayMS);
+    };
+    filterInput.oninput = filterUpdate;
+    filterRegExCheckbox.onchange = filterUpdate;
+
+    // Append the process list item after the filter item.
+    sidebarContents.appendChild(indexItem);
+  }
+
+  aProcessReports(handleReport, displayReports);
+}
+
+// ---------------------------------------------------------------------------
+
+// There are two kinds of TreeNode.
+// - Leaf TreeNodes correspond to reports.
+// - Non-leaf TreeNodes are just scaffolding nodes for the tree;  their values
+//   are derived from their children.
+// Some trees are "degenerate", i.e. they contain a single node, i.e. they
+// correspond to a report whose path has no '/' separators.
+function TreeNode(aUnsafeName, aUnits, aIsDegenerate) {
+  this._units = aUnits;
+  this._unsafeName = aUnsafeName;
+  if (aIsDegenerate) {
+    this._isDegenerate = true;
+  }
+
+  // Leaf TreeNodes have these properties added immediately after construction:
+  // - _amount
+  // - _description
+  // - _nMerged (only defined if > 1)
+  // - _presence (only defined if value is PRESENT_IN_{FIRST,SECOND}_ONLY)
+  //
+  // Non-leaf TreeNodes have these properties added later:
+  // - _kids
+  // - _amount
+  // - _description
+  // - _hideKids (only defined if true)
+  // - _maxAbsDescendant (on-demand, only when gIsDiff is set)
+}
+
+TreeNode.prototype = {
+  findKid(aUnsafeName) {
+    if (this._kids) {
+      for (let kid of this._kids) {
+        if (kid._unsafeName === aUnsafeName) {
+          return kid;
+        }
+      }
+    }
+    return undefined;
+  },
+
+  // When gIsDiff is false, tree operations -- sorting and determining if a
+  // sub-tree is significant -- are straightforward. But when gIsDiff is true,
+  // the combination of positive and negative values within a tree complicates
+  // things. So for a non-leaf node, instead of just looking at _amount, we
+  // instead look at the maximum absolute value of the node and all of its
+  // descendants.
+  maxAbsDescendant() {
+    if (!this._kids) {
+      // No kids? Just return the absolute value of the amount.
+      return Math.abs(this._amount);
+    }
+
+    if ("_maxAbsDescendant" in this) {
+      // We've computed this before? Return the saved value.
+      return this._maxAbsDescendant;
+    }
+
+    // Compute the maximum absolute value of all descendants.
+    let max = Math.abs(this._amount);
+    for (let kid of this._kids) {
+      max = Math.max(max, kid.maxAbsDescendant());
+    }
+    this._maxAbsDescendant = max;
+    return max;
+  },
+
+  toString() {
+    switch (this._units) {
+      case UNITS_BYTES:
+        return formatBytes(this._amount);
+      case UNITS_COUNT:
+      case UNITS_COUNT_CUMULATIVE:
+        return formatNum(this._amount);
+      case UNITS_PERCENTAGE:
+        return formatPercentage(this._amount);
+      default:
+        throw new Error(
+          "Invalid memory report(s): bad units in TreeNode.toString"
+        );
+    }
+  },
+};
+
+// Sort TreeNodes first by size, then by name.  The latter is important for the
+// about:memory tests, which need a predictable ordering of reporters which
+// have the same amount.
+TreeNode.compareAmounts = function (aA, aB) {
+  let a, b;
+  if (gIsDiff) {
+    a = aA.maxAbsDescendant();
+    b = aB.maxAbsDescendant();
+  } else {
+    a = aA._amount;
+    b = aB._amount;
+  }
+  if (a > b) {
+    return -1;
+  }
+  if (a < b) {
+    return 1;
+  }
+  return TreeNode.compareUnsafeNames(aA, aB);
+};
+
+TreeNode.compareUnsafeNames = function (aA, aB) {
+  return aA._unsafeName.localeCompare(aB._unsafeName);
+};
+
+/**
+ * Fill in the remaining properties for the specified tree in a bottom-up
+ * fashion.
+ *
+ * @param aRoot
+ *        The tree root.
+ */
+function fillInTree(aRoot) {
+  // Fill in the remaining properties bottom-up.
+  function fillInNonLeafNodes(aT) {
+    if (!aT._kids) {
+      // Leaf node.  Has already been filled in.
+    } else if (aT._kids.length === 1 && aT != aRoot) {
+      // Non-root, non-leaf node with one child.  Merge the child with the node
+      // to avoid redundant entries.
+      let kid = aT._kids[0];
+      let kidBytes = fillInNonLeafNodes(kid);
+      aT._unsafeName += "/" + kid._unsafeName;
+      if (kid._kids) {
+        aT._kids = kid._kids;
+      } else {
+        delete aT._kids;
+      }
+      aT._amount = kidBytes;
+      aT._description = kid._description;
+      if (kid._nMerged !== undefined) {
+        aT._nMerged = kid._nMerged;
+      }
+      assert(!aT._hideKids && !kid._hideKids, "_hideKids set when merging");
+    } else {
+      // Non-leaf node with multiple children.  Derive its _amount and
+      // _description entirely from its children...
+      let kidsBytes = 0;
+      for (let kid of aT._kids) {
+        kidsBytes += fillInNonLeafNodes(kid);
+      }
+
+      // ... except in one special case. When diffing two memory report sets,
+      // if one set has a node with children and the other has the same node
+      // but without children -- e.g. the first has "a/b/c" and "a/b/d", but
+      // the second only has "a/b" -- we need to add a fake node "a/b/(fake)"
+      // to the second to make the trees comparable. It's ugly, but it works.
+      if (
+        aT._amount !== undefined &&
+        (aT._presence === DReport.PRESENT_IN_FIRST_ONLY ||
+          aT._presence === DReport.PRESENT_IN_SECOND_ONLY)
+      ) {
+        aT._amount += kidsBytes;
+        let fake = new TreeNode("(fake child)", aT._units);
+        fake._presence = DReport.ADDED_FOR_BALANCE;
+        fake._amount = aT._amount - kidsBytes;
+        aT._kids.push(fake);
+        delete aT._presence;
+      } else {
+        assert(
+          aT._amount === undefined,
+          "_amount already set for non-leaf node"
+        );
+        aT._amount = kidsBytes;
+      }
+      aT._description = "The sum of all entries below this one.";
+    }
+    return aT._amount;
+  }
+
+  // cannotMerge is set because don't want to merge into a tree's root node.
+  fillInNonLeafNodes(aRoot);
+}
+
+/**
+ * Compute the "heap-unclassified" value and insert it into the "explicit"
+ * tree.
+ *
+ * @param aT
+ *        The "explicit" tree.
+ * @param aHeapAllocatedNode
+ *        The "heap-allocated" tree node.
+ * @param aHeapTotal
+ *        The sum of all explicit HEAP reports for this process.
+ * @return A boolean indicating if "heap-allocated" is known for the process.
+ */
+function addHeapUnclassifiedNode(aT, aHeapAllocatedNode, aHeapTotal) {
+  if (aHeapAllocatedNode === undefined) {
+    return false;
+  }
+
+  if (aT.findKid("heap-unclassified")) {
+    // heap-unclassified was already calculated, there's nothing left to do.
+    // This can happen when memory reports are exported from areweslimyet.com.
+    return true;
+  }
+
+  assert(aHeapAllocatedNode._isDegenerate, "heap-allocated is not degenerate");
+  let heapAllocatedBytes = aHeapAllocatedNode._amount;
+  let heapUnclassifiedT = new TreeNode("heap-unclassified", UNITS_BYTES);
+  heapUnclassifiedT._amount = heapAllocatedBytes - aHeapTotal;
+  heapUnclassifiedT._description =
+    "Memory not classified by a more specific report. This includes " +
+    "slop bytes due to internal fragmentation in the heap allocator " +
+    "(caused when the allocator rounds up request sizes).";
+  aT._kids.push(heapUnclassifiedT);
+  aT._amount += heapUnclassifiedT._amount;
+  return true;
+}
+
+/**
+ * Sort all kid nodes from largest to smallest, and insert aggregate nodes
+ * where appropriate.
+ *
+ * @param aTotalBytes
+ *        The size of the tree's root node.
+ * @param aT
+ *        The tree.
+ */
+function sortTreeAndInsertAggregateNodes(aTotalBytes, aT) {
+  const kSignificanceThresholdPerc = 1;
+
+  function isInsignificant(aT) {
+    if (gVerbose.checked) {
+      return false;
+    }
+
+    let perc = gIsDiff
+      ? (100 * aT.maxAbsDescendant()) / Math.abs(aTotalBytes)
+      : (100 * aT._amount) / aTotalBytes;
+    return perc < kSignificanceThresholdPerc;
+  }
+
+  if (!aT._kids) {
+    return;
+  }
+
+  aT._kids.sort(TreeNode.compareAmounts);
+
+  // If the first child is insignificant, they all are, and there's no point
+  // creating an aggregate node that lacks siblings.  Just set the parent's
+  // _hideKids property and process all children.
+  if (isInsignificant(aT._kids[0])) {
+    aT._hideKids = true;
+    for (let kid of aT._kids) {
+      sortTreeAndInsertAggregateNodes(aTotalBytes, kid);
+    }
+    return;
+  }
+
+  // Look at all children except the last one.
+  let i;
+  for (i = 0; i < aT._kids.length - 1; i++) {
+    if (isInsignificant(aT._kids[i])) {
+      // This child is below the significance threshold.  If there are other
+      // (smaller) children remaining, move them under an aggregate node.
+      let i0 = i;
+      let nAgg = aT._kids.length - i0;
+      // Create an aggregate node.  Inherit units from the parent;  everything
+      // in the tree should have the same units anyway (we test this later).
+      let aggT = new TreeNode(`(${nAgg} tiny)`, aT._units);
+      aggT._kids = [];
+      let aggBytes = 0;
+      for (; i < aT._kids.length; i++) {
+        aggBytes += aT._kids[i]._amount;
+        aggT._kids.push(aT._kids[i]);
+      }
+      aggT._hideKids = true;
+      aggT._amount = aggBytes;
+      aggT._description =
+        nAgg +
+        " sub-trees that are below the " +
+        kSignificanceThresholdPerc +
+        "% significance threshold.";
+      aT._kids.splice(i0, nAgg, aggT);
+      aT._kids.sort(TreeNode.compareAmounts);
+
+      // Process the moved children.
+      for (let kid of aggT._kids) {
+        sortTreeAndInsertAggregateNodes(aTotalBytes, kid);
+      }
+      return;
+    }
+
+    sortTreeAndInsertAggregateNodes(aTotalBytes, aT._kids[i]);
+  }
+
+  // The first n-1 children were significant.  Don't consider if the last child
+  // is significant;  there's no point creating an aggregate node that only has
+  // one child.  Just process it.
+  sortTreeAndInsertAggregateNodes(aTotalBytes, aT._kids[i]);
+}
+
+// Global variable indicating if we've seen any invalid values for this
+// process;  it holds the unsafePaths of any such reports.  It is reset for
+// each new process.
+let gUnsafePathsWithInvalidValuesForThisProcess = [];
+
+function appendWarningElements(
+  aP,
+  aHasKnownHeapAllocated,
+  aHasMozMallocUsableSize,
+  aFiltered
+) {
+  // These warnings may not make sense if the reporters they reference have been
+  // filtered out, so just skip them if we have a filter applied.
+  if (!aFiltered && !aHasKnownHeapAllocated && !aHasMozMallocUsableSize) {
+    appendElementWithText(
+      aP,
+      "p",
+      "",
+      "WARNING: the 'heap-allocated' memory reporter and the " +
+        "moz_malloc_usable_size() function do not work for this platform " +
+        "and/or configuration.  This means that 'heap-unclassified' is not " +
+        "shown and the 'explicit' tree shows much less memory than it should.\n\n"
+    );
+  } else if (!aFiltered && !aHasKnownHeapAllocated) {
+    appendElementWithText(
+      aP,
+      "p",
+      "",
+      "WARNING: the 'heap-allocated' memory reporter does not work for this " +
+        "platform and/or configuration. This means that 'heap-unclassified' " +
+        "is not shown and the 'explicit' tree shows less memory than it should.\n\n"
+    );
+  } else if (!aFiltered && !aHasMozMallocUsableSize) {
+    appendElementWithText(
+      aP,
+      "p",
+      "",
+      "WARNING: the moz_malloc_usable_size() function does not work for " +
+        "this platform and/or configuration.  This means that much of the " +
+        "heap-allocated memory is not measured by individual memory reporters " +
+        "and so will fall under 'heap-unclassified'.\n\n"
+    );
+  }
+
+  if (gUnsafePathsWithInvalidValuesForThisProcess.length) {
+    let div = appendElement(aP, "div");
+    appendElementWithText(
+      div,
+      "p",
+      "",
+      "WARNING: the following values are negative or unreasonably large.\n"
+    );
+
+    let ul = appendElement(div, "ul");
+    for (
+      let i = 0;
+      i < gUnsafePathsWithInvalidValuesForThisProcess.length;
+      i++
+    ) {
+      appendTextNode(ul, " ");
+      appendElementWithText(
+        ul,
+        "li",
+        "",
+        flipBackslashes(gUnsafePathsWithInvalidValuesForThisProcess[i]) + "\n"
+      );
+    }
+
+    appendElementWithText(
+      div,
+      "p",
+      "",
+      "This indicates a defect in one or more memory reporters.  The " +
+        "invalid values are highlighted.\n\n"
+    );
+    gUnsafePathsWithInvalidValuesForThisProcess = []; // reset for the next process
+  }
+}
+
+/**
+ * Appends the about:memory elements for a single process.
+ *
+ * @param aP
+ *        The parent DOM node.
+ * @param aN
+ *        The number of the process, starting at 0.
+ * @param aProcess
+ *        The name of the process.
+ * @param aTrees
+ *        The table of non-degenerate trees for this process.
+ * @param aDegenerates
+ *        The table of degenerate trees for this process.
+ * @param aHasMozMallocUsableSize
+ *        Boolean indicating if moz_malloc_usable_size works.
+ * @param aFiltered
+ *        Boolean indicating whether the reports were filtered.
+ * @return The generated text.
+ */
+function appendProcessAboutMemoryElements(
+  aP,
+  aN,
+  aProcess,
+  aTrees,
+  aDegenerates,
+  aHeapTotal,
+  aHasMozMallocUsableSize,
+  aFiltered
+) {
+  let appendLink = function (aHere, aThere, aArrow) {
+    let link = appendElementWithText(aP, "a", "upDownArrow", aArrow);
+    link.href = "#" + aThere + aN;
+    link.id = aHere + aN;
+    link.title = `Go to the ${aThere} of ${aProcess}`;
+    link.style = "text-decoration: none";
+
+    // This gives nice spacing when we copy and paste.
+    appendElementWithText(aP, "span", "", "\n");
+  };
+
+  appendElementWithText(aP, "h1", "", aProcess);
+  appendLink("start", "end", "↓");
+
+  // We'll fill this in later.
+  let warningsDiv = appendElement(aP, "div", "accuracyWarning");
+
+  // The explicit tree.
+  let hasExplicitTree;
+  let hasKnownHeapAllocated;
+  {
+    let treeName = "explicit";
+    let t = aTrees[treeName];
+    if (t) {
+      let pre = appendSectionHeader(aP, "Explicit Allocations");
+      hasExplicitTree = true;
+      fillInTree(t);
+      // Using the "heap-allocated" reporter here instead of
+      // nsMemoryReporterManager.heapAllocated goes against the usual pattern.
+      // But the "heap-allocated" node will go in the tree like the others, so
+      // we have to deal with it, and once we're dealing with it, it's easier
+      // to keep doing so rather than switching to the distinguished amount.
+      hasKnownHeapAllocated =
+        aDegenerates &&
+        addHeapUnclassifiedNode(t, aDegenerates["heap-allocated"], aHeapTotal);
+      sortTreeAndInsertAggregateNodes(t._amount, t);
+      t._description = explicitTreeDescription;
+      appendTreeElements(pre, t, aProcess, "");
+      delete aTrees[treeName];
+    }
+    appendTextNode(aP, "\n"); // gives nice spacing when we copy and paste
+  }
+
+  // Fill in and sort all the non-degenerate other trees.
+  let otherTrees = [];
+  for (let unsafeName in aTrees) {
+    let t = aTrees[unsafeName];
+    assert(!t._isDegenerate, "tree is degenerate");
+    fillInTree(t);
+    sortTreeAndInsertAggregateNodes(t._amount, t);
+    otherTrees.push(t);
+  }
+  otherTrees.sort(TreeNode.compareUnsafeNames);
+
+  // Get the length of the longest root value among the degenerate other trees,
+  // and sort them as well.
+  let otherDegenerates = [];
+  let maxStringLength = 0;
+  for (let unsafeName in aDegenerates) {
+    let t = aDegenerates[unsafeName];
+    assert(t._isDegenerate, "tree is not degenerate");
+    let length = t.toString().length;
+    if (length > maxStringLength) {
+      maxStringLength = length;
+    }
+    otherDegenerates.push(t);
+  }
+  otherDegenerates.sort(TreeNode.compareUnsafeNames);
+
+  // Now generate the elements, putting non-degenerate trees first.
+  if (otherTrees.length || otherDegenerates.length) {
+    let pre = appendSectionHeader(aP, "Other Measurements");
+    for (let t of otherTrees) {
+      appendTreeElements(pre, t, aProcess, "");
+      appendTextNode(pre, "\n"); // blank lines after non-degenerate trees
+    }
+    for (let t of otherDegenerates) {
+      let padText = "".padStart(maxStringLength - t.toString().length, " ");
+      appendTreeElements(pre, t, aProcess, padText);
+    }
+    appendTextNode(aP, "\n"); // gives nice spacing when we copy and paste
+  }
+
+  // Add any warnings about inaccuracies in the "explicit" tree due to platform
+  // limitations.  These must be computed after generating all the text.  The
+  // newlines give nice spacing if we copy+paste into a text buffer.
+  if (hasExplicitTree) {
+    appendWarningElements(
+      warningsDiv,
+      hasKnownHeapAllocated,
+      aHasMozMallocUsableSize,
+      aFiltered
+    );
+  }
+
+  appendElementWithText(aP, "h3", "", "End of " + aProcess);
+  appendLink("end", "start", "↑");
+}
+
+// The locale used when formatting a number as a human-readable string in any
+// format.
+const kStyleLocale = "en-US";
+
+// Used for UNITS_BYTES values that are printed as MiB.
+const kMBFormat = new Intl.NumberFormat(kStyleLocale, {
+  minimumFractionDigits: 2,
+  maximumFractionDigits: 2,
+});
+
+// Used for UNITS_PERCENTAGE values.
+const kPercFormatter = new Intl.NumberFormat(kStyleLocale, {
+  style: "percent",
+  minimumFractionDigits: 2,
+  maximumFractionDigits: 2,
+});
+
+// Used for fractions within the tree.
+const kFracFormatter = new Intl.NumberFormat(kStyleLocale, {
+  style: "percent",
+  minimumIntegerDigits: 2,
+  minimumFractionDigits: 2,
+  maximumFractionDigits: 2,
+});
+
+// Used for special-casing 100% fractions within the tree.
+const kFrac1Formatter = new Intl.NumberFormat(kStyleLocale, {
+  style: "percent",
+  minimumIntegerDigits: 3,
+  minimumFractionDigits: 1,
+  maximumFractionDigits: 1,
+});
+
+// Used when no custom formatting was requested.
+const kDefaultNumFormatter = new Intl.NumberFormat(kStyleLocale);
+
+/**
+ * Formats an int as a human-readable string.
+ *
+ * @param aN
+ *        The integer to format.
+ * @param aFormatter
+ *        Optional formatter object.
+ * @return A human-readable string representing the int.
+ */
+function formatNum(aN, aFormatter) {
+  return (aFormatter || kDefaultNumFormatter).format(aN);
+}
+
+/**
+ * Converts a byte count to an appropriate string representation.
+ *
+ * @param aBytes
+ *        The byte count.
+ * @return The string representation.
+ */
+function formatBytes(aBytes) {
+  return gVerbose.checked
+    ? `${formatNum(aBytes)} B`
+    : `${formatNum(aBytes / (1024 * 1024), kMBFormat)} MB`;
+}
+
+/**
+ * Converts a UNITS_PERCENTAGE value to an appropriate string representation.
+ *
+ * @param aPerc100x
+ *        The percentage, multiplied by 100 (see nsIMemoryReporter).
+ * @return The string representation
+ */
+function formatPercentage(aPerc100x) {
+  // A percentage like 12.34% will have an aPerc100x value of 1234, and we need
+  // to divide that by 10,000 to get the 0.1234 that toLocaleString() wants.
+  return formatNum(aPerc100x / 10000, kPercFormatter);
+}
+
+/*
+ * Converts a tree fraction to an appropriate string representation.
+ *
+ * @param aNum
+ *        The numerator.
+ * @param aDenom
+ *        The denominator.
+ * @return The string representation
+ */
+function formatTreeFrac(aNum, aDenom) {
+  // Two special behaviours here:
+  // - We treat 0 / 0 as 100%.
+  // - We want 4 digits, as much as possible, because it gives good vertical
+  //   alignment. For positive numbers, 00.00%--99.99% works straighforwardly,
+  //   but 100.0% needs special handling.
+  let num = aDenom === 0 ? 1 : aNum / aDenom;
+  return 0.99995 <= num && num <= 1
+    ? formatNum(1, kFrac1Formatter)
+    : formatNum(num, kFracFormatter);
+}
+
+const kNoKidsSep = " ── ",
+  kHideKidsSep = " ++ ",
+  kShowKidsSep = " -- ";
+
+function appendMrNameSpan(
+  aP,
+  aDescription,
+  aUnsafeName,
+  aIsInvalid,
+  aNMerged,
+  aPresence
+) {
+  let safeName = flipBackslashes(aUnsafeName);
+  if (!aIsInvalid && !aNMerged && !aPresence) {
+    safeName += "\n";
+  }
+  let nameSpan = appendElementWithText(aP, "span", "mrName", safeName);
+  nameSpan.title = aDescription;
+
+  if (aIsInvalid) {
+    let noteText = " [?!]";
+    if (!aNMerged) {
+      noteText += "\n";
+    }
+    let noteSpan = appendElementWithText(aP, "span", "mrNote", noteText);
+    noteSpan.title =
+      "Warning: this value is invalid and indicates a bug in one or more " +
+      "memory reporters. ";
+  }
+
+  if (aNMerged) {
+    let noteText = ` [${aNMerged}]`;
+    if (!aPresence) {
+      noteText += "\n";
+    }
+    let noteSpan = appendElementWithText(aP, "span", "mrNote", noteText);
+    noteSpan.title =
+      "This value is the sum of " +
+      aNMerged +
+      " memory reports that all have the same path.";
+  }
+
+  if (aPresence) {
+    let c, title;
+    switch (aPresence) {
+      case DReport.PRESENT_IN_FIRST_ONLY:
+        c = "-";
+        title =
+          "This value was only present in the first set of memory reports.";
+        break;
+      case DReport.PRESENT_IN_SECOND_ONLY:
+        c = "+";
+        title =
+          "This value was only present in the second set of memory reports.";
+        break;
+      case DReport.ADDED_FOR_BALANCE:
+        c = "!";
+        title =
+          "One of the sets of memory reports lacked children for this " +
+          "node's parent. This is a fake child node added to make the " +
+          "two memory sets comparable.";
+        break;
+      default:
+        assert(false, "bad presence");
+        break;
+    }
+    let noteSpan = appendElementWithText(aP, "span", "mrNote", ` [${c}]\n`);
+    noteSpan.title = title;
+  }
+}
+
+// This is used to record the (safe) IDs of which sub-trees have been manually
+// expanded (marked as true) and collapsed (marked as false).  It's used to
+// replicate the collapsed/expanded state when the page is updated.  It can end
+// up holding IDs of nodes that no longer exist, e.g. for compartments that
+// have been closed.  This doesn't seem like a big deal, because the number is
+// limited by the number of entries the user has changed from their original
+// state.
+let gShowSubtreesBySafeTreeId = {};
+
+function assertClassListContains(aElem, aClassName) {
+  assert(aElem, "undefined " + aClassName);
+  assert(aElem.classList.contains(aClassName), "classname isn't " + aClassName);
+}
+
+function toggle(aEvent) {
+  // This relies on each line being a span that contains at least four spans:
+  // mrValue, mrPerc, mrSep, mrName, and then zero or more mrNotes.  All
+  // whitespace must be within one of these spans for this function to find the
+  // right nodes.  And the span containing the children of this line must
+  // immediately follow.  Assertions check this.
+
+  // We want the outer span. |aEvent.target| will normally be one of the inner
+  // spans. However, if the click was dispatched via a11y, it might be the outer
+  // span because some of the inner spans are pruned from the a11y tree.
+  let outerSpan = aEvent.target.classList.contains("hasKids")
+    ? aEvent.target
+    : aEvent.target.parentNode;
+  assertClassListContains(outerSpan, "hasKids");
+
+  // Toggle the '++'/'--' separator.
+  let isExpansion;
+  let sepSpan = outerSpan.childNodes[2];
+  assertClassListContains(sepSpan, "mrSep");
+  if (sepSpan.textContent === kHideKidsSep) {
+    isExpansion = true;
+    sepSpan.textContent = kShowKidsSep;
+    outerSpan.setAttribute("aria-expanded", "true");
+  } else if (sepSpan.textContent === kShowKidsSep) {
+    isExpansion = false;
+    sepSpan.textContent = kHideKidsSep;
+    outerSpan.setAttribute("aria-expanded", "false");
+  } else {
+    assert(false, "bad sepSpan textContent");
+  }
+
+  // Toggle visibility of the span containing this node's children.
+  let subTreeSpan = outerSpan.nextSibling;
+  assertClassListContains(subTreeSpan, "kids");
+  subTreeSpan.classList.toggle("hidden");
+
+  // Record/unrecord that this sub-tree was toggled.
+  let safeTreeId = outerSpan.id;
+  if (gShowSubtreesBySafeTreeId[safeTreeId] !== undefined) {
+    delete gShowSubtreesBySafeTreeId[safeTreeId];
+  } else {
+    gShowSubtreesBySafeTreeId[safeTreeId] = isExpansion;
+  }
+}
+
+function expandPathToThisElement(aElement) {
+  if (aElement.classList.contains("kids")) {
+    // Unhide the kids.
+    aElement.classList.remove("hidden");
+    expandPathToThisElement(aElement.previousSibling); // hasKids
+  } else if (aElement.classList.contains("hasKids")) {
+    // Change the separator to '--'.
+    let sepSpan = aElement.childNodes[2];
+    assertClassListContains(sepSpan, "mrSep");
+    sepSpan.textContent = kShowKidsSep;
+    aElement.setAttribute("aria-expanded", "true");
+    expandPathToThisElement(aElement.parentNode.parentNode); // kids or pre.entries
+  } else {
+    assertClassListContains(aElement, "entries");
+  }
+}
+
+/**
+ * Appends the elements for the tree, including its heading.
+ *
+ * @param aP
+ *        The parent DOM node.
+ * @param aRoot
+ *        The tree root.
+ * @param aProcess
+ *        The process the tree corresponds to.
+ * @param aPadText
+ *        A string to pad the start of each entry.
+ */
+function appendTreeElements(aP, aRoot, aProcess, aPadText) {
+  /**
+   * Appends the elements for a particular tree, without a heading. There's a
+   * subset of the Unicode "light" box-drawing chars that is widely implemented
+   * in terminals, and this code sticks to that subset to maximize the chance
+   * that copying and pasting about:memory output to a terminal will work
+   * correctly.
+   *
+   * @param aP
+   *        The parent DOM node.
+   * @param aProcess
+   *        The process the tree corresponds to.
+   * @param aUnsafeNames
+   *        An array of the names forming the path to aT.
+   * @param aRoot
+   *        The root of the tree this sub-tree belongs to.
+   * @param aT
+   *        The tree.
+   * @param aTlThis
+   *        The treeline for this entry.
+   * @param aTlKids
+   *        The treeline for this entry's children.
+   * @param aParentStringLength
+   *        The length of the formatted byte count of the top node in the tree.
+   */
+  function appendTreeElements2(
+    aP,
+    aProcess,
+    aUnsafeNames,
+    aRoot,
+    aT,
+    aTlThis,
+    aTlKids,
+    aParentStringLength
+  ) {
+    function appendN(aS, aC, aN) {
+      for (let i = 0; i < aN; i++) {
+        aS += aC;
+      }
+      return aS;
+    }
+
+    // The entire entry including children needs to be treated as a list item
+    // for a11y purposes.
+    let p = document.createElement("span");
+    p.setAttribute("role", "listitem");
+    aP.appendChild(p);
+
+    // The tree line.  Indent more if this entry is narrower than its parent.
+    let valueText = aT.toString();
+    let extraTlLength = Math.max(aParentStringLength - valueText.length, 0);
+    if (extraTlLength > 0) {
+      aTlThis = appendN(aTlThis, "─", extraTlLength);
+      aTlKids = appendN(aTlKids, " ", extraTlLength);
+    }
+    let treeLine = appendElementWithText(p, "span", "treeline", aTlThis);
+    treeLine.setAttribute("aria-hidden", "true");
+
+    // Detect and record invalid values.  But not if gIsDiff is true, because
+    // we expect negative values in that case.
+    assertInput(
+      aRoot._units === aT._units,
+      "units within a tree are inconsistent"
+    );
+    let tIsInvalid = false;
+    if (!gIsDiff && !(0 <= aT._amount && aT._amount <= aRoot._amount)) {
+      tIsInvalid = true;
+      let unsafePath = aUnsafeNames.join("/");
+      gUnsafePathsWithInvalidValuesForThisProcess.push(unsafePath);
+      reportAssertionFailure(
+        `Invalid value (${aT._amount} / ${aRoot._amount}) for ` +
+          flipBackslashes(unsafePath)
+      );
+    }
+
+    // For non-leaf nodes, the entire sub-tree is put within a span so it can
+    // be collapsed if the node is clicked on.
+    let d;
+    let sep;
+    let showSubtrees;
+    if (aT._kids) {
+      // Determine if we should show the sub-tree below this entry;  this
+      // involves reinstating any previous toggling of the sub-tree.
+      let unsafePath = aUnsafeNames.join("/");
+      let safeTreeId = `${aProcess}:${flipBackslashes(unsafePath)}`;
+      showSubtrees = !aT._hideKids;
+      if (gShowSubtreesBySafeTreeId[safeTreeId] !== undefined) {
+        showSubtrees = gShowSubtreesBySafeTreeId[safeTreeId];
+      }
+      d = appendElement(p, "span", "hasKids");
+      d.id = safeTreeId;
+      d.onclick = toggle;
+      d.setAttribute("role", "button");
+      sep = showSubtrees ? kShowKidsSep : kHideKidsSep;
+      d.setAttribute("aria-expanded", showSubtrees ? "true" : "false");
+    } else {
+      assert(!aT._hideKids, "leaf node with _hideKids set");
+      sep = kNoKidsSep;
+      d = p;
+    }
+
+    // The value.
+    appendElementWithText(
+      d,
+      "span",
+      "mrValue" + (tIsInvalid ? " invalid" : ""),
+      valueText
+    );
+
+    // The percentage (omitted for single entries).
+    if (!aT._isDegenerate) {
+      let percText = formatTreeFrac(aT._amount, aRoot._amount);
+      appendElementWithText(d, "span", "mrPerc", ` (${percText})`);
+    }
+
+    // The separator.
+    appendElementWithText(d, "span", "mrSep", sep);
+
+    // The entry's name.
+    appendMrNameSpan(
+      d,
+      aT._description,
+      aT._unsafeName,
+      tIsInvalid,
+      aT._nMerged,
+      aT._presence
+    );
+
+    // In non-verbose mode, invalid nodes can be hidden in collapsed sub-trees.
+    // But it's good to always see them, so force this.
+    if (!gVerbose.checked && tIsInvalid) {
+      expandPathToThisElement(aT._kids ? d : aP);
+    }
+
+    // Recurse over children.
+    if (aT._kids) {
+      // The 'kids' class is just used for sanity checking in toggle().
+      d = appendElement(p, "span", showSubtrees ? "kids" : "kids hidden");
+      d.setAttribute("role", "list");
+
+      let tlThisForMost, tlKidsForMost;
+      if (aT._kids.length > 1) {
+        tlThisForMost = aTlKids + "├──";
+        tlKidsForMost = aTlKids + "│  ";
+      }
+      let tlThisForLast = aTlKids + "└──";
+      let tlKidsForLast = aTlKids + "   ";
+
+      for (let [i, kid] of aT._kids.entries()) {
+        let isLast = i == aT._kids.length - 1;
+        aUnsafeNames.push(kid._unsafeName);
+        appendTreeElements2(
+          d,
+          aProcess,
+          aUnsafeNames,
+          aRoot,
+          kid,
+          !isLast ? tlThisForMost : tlThisForLast,
+          !isLast ? tlKidsForMost : tlKidsForLast,
+          valueText.length
+        );
+        aUnsafeNames.pop();
+      }
+    }
+  }
+
+  let rootStringLength = aRoot.toString().length;
+  appendTreeElements2(
+    aP,
+    aProcess,
+    [aRoot._unsafeName],
+    aRoot,
+    aRoot,
+    aPadText,
+    aPadText,
+    rootStringLength
+  );
+}
+
+// ---------------------------------------------------------------------------
+
+function appendSectionHeader(aP, aText) {
+  appendElementWithText(aP, "h2", "", aText + "\n");
+  let entries = appendElement(aP, "pre", "entries");
+  entries.setAttribute("role", "list");
+  return entries;
+}
+
+// ---------------------------------------------------------------------------
+
+function saveReportsToFile() {
+  let fp = Cc["@mozilla.org/filepicker;1"].createInstance(Ci.nsIFilePicker);
+  fp.appendFilter("Zipped JSON files", "*.json.gz");
+  fp.appendFilters(Ci.nsIFilePicker.filterAll);
+  fp.filterIndex = 0;
+  fp.addToRecentDocs = true;
+  fp.defaultString = "memory-report.json.gz";
+
+  let fpFinish = function (aFile) {
+    let dumper = Cc["@mozilla.org/memory-info-dumper;1"].getService(
+      Ci.nsIMemoryInfoDumper
+    );
+    let finishDumping = () => {
+      updateMainAndFooter(
+        "Saved memory reports to " + aFile.path,
+        SHOW_TIMESTAMP,
+        HIDE_FOOTER
+      );
+    };
+    dumper.dumpMemoryReportsToNamedFile(
+      aFile.path,
+      finishDumping,
+      null,
+      gAnonymize.checked,
+      /* minimize memory usage = */ false
+    );
+  };
+
+  let fpCallback = function (aResult) {
+    if (
+      aResult == Ci.nsIFilePicker.returnOK ||
+      aResult == Ci.nsIFilePicker.returnReplace
+    ) {
+      fpFinish(fp.file);
+    }
+  };
+
+  try {
+    fp.init(window, "Save Memory Reports", Ci.nsIFilePicker.modeSave);
+  } catch (ex) {
+    // This will fail on Android, since there is no Save as file picker there.
+    // Just save to the default downloads dir if it does.
+    Downloads.getSystemDownloadsDirectory().then(function (aDirPath) {
+      let file = FileUtils.File(aDirPath);
+      file.append(fp.defaultString);
+      fpFinish(file);
+    });
+
+    return;
+  }
+  fp.open(fpCallback);
+}
diff --git a/toolkit/components/aboutmemory/content/aboutMemory.xhtml b/toolkit/components/aboutmemory/content/aboutMemory.xhtml
new file mode 100644
index 0000000000..999f0b449a
--- /dev/null
+++ b/toolkit/components/aboutmemory/content/aboutMemory.xhtml
@@ -0,0 +1,35 @@
+<?xml version="1.0"?>
+
+<!-- This Source Code Form is subject to the terms of the Mozilla Public
+   - License, v. 2.0. If a copy of the MPL was not distributed with this
+   - file, You can obtain one at http://mozilla.org/MPL/2.0/. -->
+
+<!-- We explicitly set the language to English, which more-or-less guarantees
+     that the box-drawing characters used are the correct width. Without that,
+     in a Japanese or Chinese locale we might end up with box-drawing
+     characters that are twice the width of English characters, which messes up
+     the tree layout. See bug 1561153 for details. Note that about:memory is
+     not localized, so setting it explicitly to English should be fine.
+
+     We also set the fonts in aboutMemory.css in such a way that maximizes the
+     chances that the font chosen supports the box-drawing chars.
+-->
+<html xmlns="http://www.w3.org/1999/xhtml" lang="en">
+  <head>
+    <meta
+      http-equiv="Content-Security-Policy"
+      content="default-src chrome:; object-src 'none'"
+    />
+    <meta name="viewport" content="width=device-width" />
+    <meta name="color-scheme" content="light dark" />
+    <title>Memory Analyzer</title>
+    <link
+      rel="stylesheet"
+      href="chrome://global/skin/aboutMemory.css"
+      type="text/css"
+    />
+    <script src="chrome://global/content/aboutMemory.js" />
+  </head>
+
+  <body></body>
+</html>
diff --git a/toolkit/components/aboutmemory/jar.mn b/toolkit/components/aboutmemory/jar.mn
new file mode 100644
index 0000000000..0a6b01ed78
--- /dev/null
+++ b/toolkit/components/aboutmemory/jar.mn
@@ -0,0 +1,8 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+toolkit.jar:
+  content/global/aboutMemory.js                        (content/aboutMemory.js)
+  content/global/aboutMemory.xhtml                     (content/aboutMemory.xhtml)
+  content/global/aboutMemory.css                       (content/aboutMemory.css)
diff --git a/toolkit/components/aboutmemory/moz.build b/toolkit/components/aboutmemory/moz.build
new file mode 100644
index 0000000000..017d8d1264
--- /dev/null
+++ b/toolkit/components/aboutmemory/moz.build
@@ -0,0 +1,15 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+MOCHITEST_CHROME_MANIFESTS += ["tests/chrome.ini"]
+XPCSHELL_TESTS_MANIFESTS += [
+    "tests/xpcshell/xpcshell.ini",
+]
+
+JAR_MANIFESTS += ["jar.mn"]
+
+with Files("**"):
+    BUG_COMPONENT = ("Toolkit", "about:memory")
diff --git a/toolkit/components/aboutmemory/tests/chrome.ini b/toolkit/components/aboutmemory/tests/chrome.ini
new file mode 100644
index 0000000000..4e5071e4a0
--- /dev/null
+++ b/toolkit/components/aboutmemory/tests/chrome.ini
@@ -0,0 +1,31 @@
+[DEFAULT]
+skip-if = os == 'android'
+support-files =
+  crash-dump-diff1.json
+  crash-dump-diff2.json
+  crash-dump-good.json
+  fiss-diff1.json
+  fiss-diff2.json
+  memory-reports-bad.json
+  memory-reports-diff1.json
+  memory-reports-diff2.json
+  memory-reports-good.json
+  remote.xhtml
+
+[test_aboutmemory.xhtml]
+[test_aboutmemory2.xhtml]
+[test_aboutmemory3.xhtml]
+[test_aboutmemory4.xhtml]
+skip-if =
+  os == "linux" && bits == 64 && debug # Bug 1683002
+[test_aboutmemory5.xhtml]
+skip-if = 
+  asan # Bug 1116230 
+  os == "linux" && bits == 64 && debug # Bug 1683002
+[test_aboutmemory6.xhtml]
+[test_aboutmemory7.xhtml]
+[test_memoryReporters.xhtml]
+[test_memoryReporters2.xhtml]
+[test_sqliteMultiReporter.xhtml]
+[test_dumpGCAndCCLogsToFile.xhtml]
+skip-if = (verify && debug && (os == 'mac'))
diff --git a/toolkit/components/aboutmemory/tests/crash-dump-diff1.json b/toolkit/components/aboutmemory/tests/crash-dump-diff1.json
new file mode 100644
index 0000000000..2b9c6921a8
--- /dev/null
+++ b/toolkit/components/aboutmemory/tests/crash-dump-diff1.json
@@ -0,0 +1,18 @@
+{
+  "foo": 1,
+  "blah": 2,
+  "memory_report": {
+    "version": 1,
+    "hasMozMallocUsableSize": true,
+    "reports": [
+      {
+        "process": "Main Process (pid NNN)",
+        "path": "heap-allocated",
+        "kind": 2,
+        "units": 0,
+        "amount": 262144000,
+        "description": "Heap allocated."
+      }
+    ]
+  }
+}
diff --git a/toolkit/components/aboutmemory/tests/crash-dump-diff2.json b/toolkit/components/aboutmemory/tests/crash-dump-diff2.json
new file mode 100644
index 0000000000..15ddf2831c
--- /dev/null
+++ b/toolkit/components/aboutmemory/tests/crash-dump-diff2.json
@@ -0,0 +1,18 @@
+{
+  "foo": 3,
+  "blah": 4,
+  "memory_report": {
+    "version": 1,
+    "hasMozMallocUsableSize": true,
+    "reports": [
+      {
+        "process": "Main Process (pid NNN)",
+        "path": "heap-allocated",
+        "kind": 2,
+        "units": 0,
+        "amount": 262144001,
+        "description": "Heap allocated."
+      }
+    ]
+  }
+}
diff --git a/toolkit/components/aboutmemory/tests/crash-dump-good.json b/toolkit/components/aboutmemory/tests/crash-dump-good.json
new file mode 100644
index 0000000000..7865369dc3
--- /dev/null
+++ b/toolkit/components/aboutmemory/tests/crash-dump-good.json
@@ -0,0 +1,42 @@
+{
+  "foo": 1,
+  "blah": 2,
+  "memory_report": {
+    "version": 1,
+    "hasMozMallocUsableSize": true,
+    "reports": [
+      {
+        "process": "Main Process (pid NNN)",
+        "path": "heap-allocated",
+        "kind": 2,
+        "units": 0,
+        "amount": 262144000,
+        "description": "Heap allocated."
+      },
+      {
+        "process": "Main Process (pid NNN)",
+        "path": "other/b",
+        "kind": 2,
+        "units": 0,
+        "amount": 104857,
+        "description": "Other b."
+      },
+      {
+        "process": "Main Process (pid NNN)",
+        "path": "other/a",
+        "kind": 2,
+        "units": 0,
+        "amount": 209715,
+        "description": "Other a."
+      },
+      {
+        "process": "Main Process (pid NNN)",
+        "path": "explicit/a/b",
+        "kind": 1,
+        "units": 0,
+        "amount": 52428800,
+        "description": "A b."
+      }
+    ]
+  }
+}
diff --git a/toolkit/components/aboutmemory/tests/fiss-diff1.json b/toolkit/components/aboutmemory/tests/fiss-diff1.json
new file mode 100644
index 0000000000..abd06bb508
--- /dev/null
+++ b/toolkit/components/aboutmemory/tests/fiss-diff1.json
@@ -0,0 +1,59 @@
+{
+  "foo": 1,
+  "blah": 2,
+  "memory_report": {
+    "version": 1,
+    "hasMozMallocUsableSize": true,
+    "reports": [
+      {
+        "process": "P (pid 12345)",
+        "path": "explicit/foobar",
+        "kind": 1,
+        "units": 0,
+        "amount": 100,
+        "description": "Desc."
+      },
+      {
+        "process": "P (pid 12345)",
+        "path": "explicit/zero1",
+        "kind": 1,
+        "units": 0,
+        "amount": 0,
+        "description": "Desc."
+      },
+      {
+        "process": "P (pid 12345)",
+        "path": "heap-allocated",
+        "kind": 2,
+        "units": 0,
+        "amount": 10000000,
+        "description": "Heap allocated."
+      },
+
+      {
+        "process": "web (pid 12345)",
+        "path": "explicit/a/b",
+        "kind": 1,
+        "units": 0,
+        "amount": 2000000,
+        "description": "Desc."
+      },
+      {
+        "process": "web (pid 12345)",
+        "path": "explicit/a/c/d",
+        "kind": 1,
+        "units": 0,
+        "amount": 2000000,
+        "description": "Desc."
+      },
+      {
+        "process": "web (pid 12345)",
+        "path": "heap-allocated",
+        "kind": 2,
+        "units": 0,
+        "amount": 10000000,
+        "description": "Heap allocated."
+      }
+    ]
+  }
+}
diff --git a/toolkit/components/aboutmemory/tests/fiss-diff2.json b/toolkit/components/aboutmemory/tests/fiss-diff2.json
new file mode 100644
index 0000000000..286d2dd8ec
--- /dev/null
+++ b/toolkit/components/aboutmemory/tests/fiss-diff2.json
@@ -0,0 +1,59 @@
+{
+  "foo": 1,
+  "blah": 2,
+  "memory_report": {
+    "version": 1,
+    "hasMozMallocUsableSize": true,
+    "reports": [
+      {
+        "process": "P (pid 12345)",
+        "path": "explicit/foobar",
+        "kind": 1,
+        "units": 0,
+        "amount": 400,
+        "description": "Desc."
+      },
+      {
+        "process": "P (pid 12345)",
+        "path": "explicit/zero1",
+        "kind": 1,
+        "units": 0,
+        "amount": 0,
+        "description": "Desc."
+      },
+      {
+        "process": "P (pid 12345)",
+        "path": "heap-allocated",
+        "kind": 2,
+        "units": 0,
+        "amount": 13000000,
+        "description": "Heap allocated."
+      },
+
+      {
+        "process": "webIsolated=https://example.com (pid 12345)",
+        "path": "explicit/a/b",
+        "kind": 1,
+        "units": 0,
+        "amount": 2000000,
+        "description": "Desc."
+      },
+      {
+        "process": "webIsolated=https://example.com (pid 12345)",
+        "path": "explicit/a/c/d",
+        "kind": 1,
+        "units": 0,
+        "amount": 3000000,
+        "description": "Desc."
+      },
+      {
+        "process": "webIsolated=https://example.com (pid 12345)",
+        "path": "heap-allocated",
+        "kind": 2,
+        "units": 0,
+        "amount": 12000000,
+        "description": "Heap allocated."
+      }
+    ]
+  }
+}
diff --git a/toolkit/components/aboutmemory/tests/memory-reports-bad.json b/toolkit/components/aboutmemory/tests/memory-reports-bad.json
new file mode 100644
index 0000000000..61a2092b1b
--- /dev/null
+++ b/toolkit/components/aboutmemory/tests/memory-reports-bad.json
@@ -0,0 +1,3 @@
+{
+  "version": 1
+}
diff --git a/toolkit/components/aboutmemory/tests/memory-reports-diff1.json b/toolkit/components/aboutmemory/tests/memory-reports-diff1.json
new file mode 100644
index 0000000000..bdc0eda14b
--- /dev/null
+++ b/toolkit/components/aboutmemory/tests/memory-reports-diff1.json
@@ -0,0 +1,272 @@
+{
+  "version": 1,
+  "hasMozMallocUsableSize": true,
+  "reports": [
+    {
+      "process": "P",
+      "path": "explicit/xpcom/category-manager",
+      "kind": 1,
+      "units": 0,
+      "amount": 56848,
+      "description": "Desc."
+    },
+    {
+      "process": "P",
+      "path": "explicit/storage/prefixset/goog-phish-shavar",
+      "kind": 1,
+      "units": 0,
+      "amount": 680000,
+      "description": "Desc."
+    },
+
+    {
+      "process": "P",
+      "path": "explicit/spell-check",
+      "kind": 1,
+      "units": 0,
+      "amount": 4,
+      "description": "Desc."
+    },
+    {
+      "process": "P",
+      "path": "explicit/spell-check",
+      "kind": 1,
+      "units": 0,
+      "amount": 5,
+      "description": "Desc."
+    },
+
+    {
+      "process": "P",
+      "path": "page-faults-soft",
+      "kind": 2,
+      "units": 2,
+      "amount": 61013,
+      "description": "Desc."
+    },
+
+    {
+      "process": "P",
+      "path": "foobar",
+      "kind": 2,
+      "units": 0,
+      "amount": 100,
+      "description": "Desc."
+    },
+    {
+      "process": "P",
+      "path": "zero1",
+      "kind": 2,
+      "units": 0,
+      "amount": 0,
+      "description": "Desc."
+    },
+
+    {
+      "process": "P",
+      "path": "a/b",
+      "kind": 2,
+      "units": 0,
+      "amount": 1000000,
+      "description": "Desc."
+    },
+    {
+      "process": "P",
+      "path": "a/c/d",
+      "kind": 2,
+      "units": 0,
+      "amount": 2000000,
+      "description": "Desc."
+    },
+    {
+      "process": "P",
+      "path": "a/c/e",
+      "kind": 2,
+      "units": 0,
+      "amount": 2000000,
+      "description": "Desc."
+    },
+    {
+      "process": "P",
+      "path": "a/c/f",
+      "kind": 2,
+      "units": 0,
+      "amount": 3000000,
+      "description": "Desc."
+    },
+    {
+      "process": "P",
+      "path": "a/c/g",
+      "kind": 2,
+      "units": 0,
+      "amount": 3000000,
+      "description": "Desc."
+    },
+    {
+      "process": "P",
+      "path": "a/h",
+      "kind": 2,
+      "units": 0,
+      "amount": 1000,
+      "description": "Desc."
+    },
+
+    {
+      "process": "P2 (pid 22)",
+      "path": "p1 (pid 123)",
+      "kind": 2,
+      "units": 0,
+      "amount": 33,
+      "description": "Desc."
+    },
+    {
+      "process": "P2 (pid 22)",
+      "path": "p2 (blah, pid=123)",
+      "kind": 2,
+      "units": 0,
+      "amount": 33,
+      "description": "Desc."
+    },
+    {
+      "process": "P2 (pid 22)",
+      "path": "p3/zone(0x1234)/p3",
+      "kind": 2,
+      "units": 0,
+      "amount": 33,
+      "description": "Desc."
+    },
+    {
+      "process": "P2 (pid 22)",
+      "path": "p4/js-zone(0x1234)/p4",
+      "kind": 2,
+      "units": 0,
+      "amount": 33,
+      "description": "Desc."
+    },
+    {
+      "process": "P2 (pid 22)",
+      "path": "p5/worker(foo.com, 0x1234)/p5",
+      "kind": 2,
+      "units": 0,
+      "amount": 33,
+      "description": "Desc."
+    },
+    {
+      "process": "P2 (pid 22)",
+      "path": "explicit/window-objects/top(bar.com, id=123)/...",
+      "kind": 0,
+      "units": 0,
+      "amount": 33,
+      "description": "Desc."
+    },
+    {
+      "process": "P2 (pid 22)",
+      "path": "p6/z-moz-nullprincipal:{85e250f3-57ae-46c4-a11e-4176dd39d9c5}/p6",
+      "kind": 2,
+      "units": 0,
+      "amount": 33,
+      "description": "Desc."
+    },
+    {
+      "process": "P2 (pid 22)",
+      "path": "p7/js-main-runtime-compartments/system/jar:file:\\\\\\temp_xyz\\firefox\\omni.ja!/p7",
+      "kind": 2,
+      "units": 0,
+      "amount": 33,
+      "description": "Desc."
+    },
+    {
+      "process": "P2 (pid 22)",
+      "path": "explicit/js-non-window/runtime/script-sources/source(scripts=1011, <non-notable files>)/misc",
+      "kind": 2,
+      "units": 0,
+      "amount": 33,
+      "description": "Desc."
+    },
+
+    {
+      "process": "P3",
+      "path": "p3",
+      "kind": 2,
+      "units": 0,
+      "amount": 55,
+      "description": "Desc."
+    },
+
+    {
+      "process": "P5",
+      "path": "p5",
+      "kind": 2,
+      "units": 0,
+      "amount": 0,
+      "description": "Desc."
+    },
+
+    {
+      "process": "P7",
+      "path": "p7",
+      "kind": 2,
+      "units": 0,
+      "amount": 5,
+      "description": "Desc."
+    },
+
+    {
+      "process": "P8",
+      "path": "p8/a/b/c/d",
+      "kind": 2,
+      "units": 0,
+      "amount": 3,
+      "description": "Desc."
+    },
+    {
+      "process": "P8",
+      "path": "p8/a/b/c/e",
+      "kind": 2,
+      "units": 0,
+      "amount": 4,
+      "description": "Desc."
+    },
+    {
+      "process": "P8",
+      "path": "p8/a/b/f",
+      "kind": 2,
+      "units": 0,
+      "amount": 5,
+      "description": "Desc."
+    },
+    {
+      "process": "P8",
+      "path": "p8/a/g/h",
+      "kind": 2,
+      "units": 0,
+      "amount": 6,
+      "description": "Desc."
+    },
+    {
+      "process": "P8",
+      "path": "p8/a/g/i",
+      "kind": 2,
+      "units": 0,
+      "amount": 7,
+      "description": "Desc."
+    },
+
+    {
+      "process": "P9",
+      "path": "explicit/threads/stacks/DNS Resolver #1 (tid=11)",
+      "kind": 0,
+      "units": 0,
+      "amount": 2000,
+      "description": "Desc."
+    },
+    {
+      "process": "P9",
+      "path": "explicit/threads/stacks/DNS Resolver #2 (tid=22)",
+      "kind": 0,
+      "units": 0,
+      "amount": 4000,
+      "description": "Desc."
+    }
+  ]
+}
diff --git a/toolkit/components/aboutmemory/tests/memory-reports-diff2.json b/toolkit/components/aboutmemory/tests/memory-reports-diff2.json
new file mode 100644
index 0000000000..d6cd988988
--- /dev/null
+++ b/toolkit/components/aboutmemory/tests/memory-reports-diff2.json
@@ -0,0 +1,265 @@
+{
+  "version": 1,
+  "hasMozMallocUsableSize": true,
+  "reports": [
+    {
+      "process": "P",
+      "path": "explicit/xpcom/category-manager",
+      "kind": 1,
+      "units": 0,
+      "amount": 56849,
+      "description": "Desc."
+    },
+    {
+      "process": "P",
+      "path": "explicit/storage/prefixset/goog-phish-shavar",
+      "kind": 1,
+      "units": 0,
+      "amount": 670000,
+      "description": "Desc."
+    },
+
+    {
+      "process": "P",
+      "path": "explicit/spell-check",
+      "kind": 1,
+      "units": 0,
+      "amount": 3,
+      "description": "Desc."
+    },
+
+    {
+      "process": "P",
+      "path": "page-faults-soft",
+      "kind": 2,
+      "units": 2,
+      "amount": 61013,
+      "description": "Desc."
+    },
+
+    {
+      "process": "P",
+      "path": "canvas-2d-pixel-bytes",
+      "kind": 2,
+      "units": 0,
+      "amount": 1000,
+      "description": "Desc."
+    },
+    {
+      "process": "P",
+      "path": "canvas-2d-pixel-bytes",
+      "kind": 2,
+      "units": 0,
+      "amount": 2000,
+      "description": "Desc."
+    },
+
+    {
+      "process": "P",
+      "path": "foobaz",
+      "kind": 2,
+      "units": 0,
+      "amount": 0,
+      "description": "Desc."
+    },
+
+    {
+      "process": "P",
+      "path": "a/b",
+      "kind": 2,
+      "units": 0,
+      "amount": 2000000,
+      "description": "Desc."
+    },
+    {
+      "process": "P",
+      "path": "a/c/d",
+      "kind": 2,
+      "units": 0,
+      "amount": 2998000,
+      "description": "Desc."
+    },
+    {
+      "process": "P",
+      "path": "a/c/e",
+      "kind": 2,
+      "units": 0,
+      "amount": 1001000,
+      "description": "Desc."
+    },
+    {
+      "process": "P",
+      "path": "a/c/f",
+      "kind": 2,
+      "units": 0,
+      "amount": 3001000,
+      "description": "Desc."
+    },
+    {
+      "process": "P",
+      "path": "a/c/g",
+      "kind": 2,
+      "units": 0,
+      "amount": 3001000,
+      "description": "Desc."
+    },
+    {
+      "process": "P",
+      "path": "a/h",
+      "kind": 2,
+      "units": 0,
+      "amount": 2000,
+      "description": "Desc."
+    },
+
+    {
+      "process": "P2 (pid 22)",
+      "path": "p1 (pid 456)",
+      "kind": 2,
+      "units": 0,
+      "amount": 44,
+      "description": "Desc."
+    },
+    {
+      "process": "P2 (pid 22)",
+      "path": "p2 (blah, pid=456)",
+      "kind": 2,
+      "units": 0,
+      "amount": 44,
+      "description": "Desc."
+    },
+    {
+      "process": "P2 (pid 22)",
+      "path": "p3/zone(0x5678)/p3",
+      "kind": 2,
+      "units": 0,
+      "amount": 44,
+      "description": "Desc."
+    },
+    {
+      "process": "P2 (pid 22)",
+      "path": "p4/js-zone(0x5678)/p4",
+      "kind": 2,
+      "units": 0,
+      "amount": 44,
+      "description": "Desc."
+    },
+    {
+      "process": "P2 (pid 22)",
+      "path": "p5/worker(foo.com, 0x5678)/p5",
+      "kind": 2,
+      "units": 0,
+      "amount": 44,
+      "description": "Desc."
+    },
+    {
+      "process": "P2 (pid 22)",
+      "path": "explicit/window-objects/top(bar.com, id=456)/...",
+      "kind": 0,
+      "units": 0,
+      "amount": 44,
+      "description": "Desc."
+    },
+    {
+      "process": "P2 (pid 22)",
+      "path": "p6/z-moz-nullprincipal:{161effaa-c1f7-4010-a08e-e7c9aea01aed}/p6",
+      "kind": 2,
+      "units": 0,
+      "amount": 44,
+      "description": "Desc."
+    },
+    {
+      "process": "P2 (pid 22)",
+      "path": "p7/js-main-runtime-compartments/system/jar:file:\\\\\\temp_abc\\firefox\\omni.ja!/p7",
+      "kind": 2,
+      "units": 0,
+      "amount": 44,
+      "description": "Desc."
+    },
+    {
+      "process": "P2 (pid 22)",
+      "path": "explicit/js-non-window/runtime/script-sources/source(scripts=1, <non-notable files>)/misc",
+      "kind": 2,
+      "units": 0,
+      "amount": 33,
+      "description": "Desc."
+    },
+
+    {
+      "process": "P4",
+      "path": "p4",
+      "kind": 2,
+      "units": 0,
+      "amount": 66,
+      "description": "Desc."
+    },
+
+    {
+      "process": "P6",
+      "path": "p6",
+      "kind": 2,
+      "units": 0,
+      "amount": 0,
+      "description": "Desc."
+    },
+
+    {
+      "process": "P7",
+      "path": "p7/b",
+      "kind": 2,
+      "units": 0,
+      "amount": 3,
+      "description": "Desc."
+    },
+    {
+      "process": "P7",
+      "path": "p7/c",
+      "kind": 2,
+      "units": 0,
+      "amount": 4,
+      "description": "Desc."
+    },
+
+    {
+      "process": "P8",
+      "path": "p8/a/b",
+      "kind": 2,
+      "units": 0,
+      "amount": 1,
+      "description": "Desc."
+    },
+    {
+      "process": "P8",
+      "path": "p8/a/g",
+      "kind": 2,
+      "units": 0,
+      "amount": 2,
+      "description": "Desc."
+    },
+
+    {
+      "process": "P9",
+      "path": "explicit/threads/stacks/DNS Resolver #1 (tid=33)",
+      "kind": 0,
+      "units": 0,
+      "amount": 2000,
+      "description": "Desc."
+    },
+    {
+      "process": "P9",
+      "path": "explicit/threads/stacks/DNS Resolver #2 (tid=44)",
+      "kind": 0,
+      "units": 0,
+      "amount": 4000,
+      "description": "Desc."
+    },
+    {
+      "process": "P9",
+      "path": "explicit/threads/stacks/DNS Resolver #3 (tid=45)",
+      "kind": 0,
+      "units": 0,
+      "amount": 5000,
+      "description": "Desc."
+    }
+  ]
+}
diff --git a/toolkit/components/aboutmemory/tests/memory-reports-good.json b/toolkit/components/aboutmemory/tests/memory-reports-good.json
new file mode 100644
index 0000000000..21b6d5b0aa
--- /dev/null
+++ b/toolkit/components/aboutmemory/tests/memory-reports-good.json
@@ -0,0 +1,146 @@
+{
+  "version": 1,
+  "hasMozMallocUsableSize": true,
+  "reports": [
+    {
+      "process": "Main Process (pid NNN)",
+      "path": "heap-allocated",
+      "kind": 2,
+      "units": 0,
+      "amount": 262144000,
+      "description": "Heap allocated."
+    },
+    {
+      "process": "Main Process (pid NNN)",
+      "path": "other/b",
+      "kind": 2,
+      "units": 0,
+      "amount": 104857,
+      "description": "Other b."
+    },
+    {
+      "process": "Main Process (pid NNN)",
+      "path": "other/a",
+      "kind": 2,
+      "units": 0,
+      "amount": 209715,
+      "description": "Other a."
+    },
+    {
+      "process": "Main Process (pid NNN)",
+      "path": "explicit/a/b",
+      "kind": 1,
+      "units": 0,
+      "amount": 52428800,
+      "description": "A b."
+    },
+
+    {
+      "process": "Main Process (pid NNN)",
+      "path": "size/a",
+      "kind": 1,
+      "units": 0,
+      "amount": 1024,
+      "description": "non-sentence"
+    },
+    {
+      "process": "Main Process (pid NNN)",
+      "path": "rss/a",
+      "kind": 1,
+      "units": 0,
+      "amount": 1024,
+      "description": "non-sentence"
+    },
+    {
+      "process": "Main Process (pid NNN)",
+      "path": "pss/a",
+      "kind": 1,
+      "units": 0,
+      "amount": 1024,
+      "description": "non-sentence"
+    },
+    {
+      "process": "Main Process (pid NNN)",
+      "path": "swap/a",
+      "kind": 1,
+      "units": 0,
+      "amount": 1024,
+      "description": "non-sentence"
+    },
+    {
+      "process": "Main Process (pid NNN)",
+      "path": "compartments/system/a",
+      "kind": 1,
+      "units": 0,
+      "amount": 1024,
+      "description": ""
+    },
+    {
+      "process": "Main Process (pid NNN)",
+      "path": "ghost-windows/a",
+      "kind": 1,
+      "units": 0,
+      "amount": 1024,
+      "description": ""
+    },
+
+    {
+      "process": "Heap-unclassified process",
+      "path": "heap-allocated",
+      "kind": 2,
+      "units": 0,
+      "amount": 262144000,
+      "description": "Heap allocated."
+    },
+    {
+      "process": "Heap-unclassified process",
+      "path": "explicit/a/b",
+      "kind": 1,
+      "units": 0,
+      "amount": 52428800,
+      "description": "A b."
+    },
+    {
+      "process": "Heap-unclassified process",
+      "path": "explicit/heap-unclassified",
+      "kind": 1,
+      "units": 0,
+      "amount": 209715200,
+      "description": "Heap unclassified"
+    },
+
+    {
+      "process": "Explicit-only process",
+      "path": "explicit/a/b",
+      "kind": 1,
+      "units": 0,
+      "amount": 100000,
+      "description": "A b."
+    },
+
+    {
+      "process": "Other-only process",
+      "path": "a/b",
+      "kind": 1,
+      "units": 0,
+      "amount": 100000,
+      "description": "A b."
+    },
+    {
+      "process": "Other-only process",
+      "path": "a/c",
+      "kind": 1,
+      "units": 0,
+      "amount": 100000,
+      "description": "A c."
+    },
+    {
+      "process": "Other-only process",
+      "path": "heap-allocated",
+      "kind": 1,
+      "units": 0,
+      "amount": 500000,
+      "description": "D."
+    }
+  ]
+}
diff --git a/toolkit/components/aboutmemory/tests/remote.xhtml b/toolkit/components/aboutmemory/tests/remote.xhtml
new file mode 100644
index 0000000000..7d69101305
--- /dev/null
+++ b/toolkit/components/aboutmemory/tests/remote.xhtml
@@ -0,0 +1,12 @@
+<?xml version="1.0"?>
+<?xml-stylesheet href="chrome://global/skin" type="text/css"?>
+<?xml-stylesheet href="chrome://mochikit/content/tests/SimpleTest/test.css"
+                 type="text/css"?>
+<window title="Remote browser"
+  xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul">
+
+  <!-- test results are displayed in the html:body -->
+  <p>Remote browser</p>
+
+  <browser type="content" src="about:blank" id="remote" remote="true"/>
+</window>
diff --git a/toolkit/components/aboutmemory/tests/test_aboutmemory.xhtml b/toolkit/components/aboutmemory/tests/test_aboutmemory.xhtml
new file mode 100644
index 0000000000..4617a019ad
--- /dev/null
+++ b/toolkit/components/aboutmemory/tests/test_aboutmemory.xhtml
@@ -0,0 +1,599 @@
+<?xml version="1.0"?>
+<?xml-stylesheet type="text/css" href="chrome://global/skin"?>
+<?xml-stylesheet type="text/css" href="chrome://mochikit/content/tests/SimpleTest/test.css"?>
+<window title="about:memory"
+        xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul">
+  <script src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"/>
+  <script src="chrome://mochikit/content/tests/SimpleTest/EventUtils.js"></script>
+
+  <!-- This file uses fake memory reporters to test the presentation of memory
+       reports in about:memory.  test_memoryReporters.xhtml uses the real
+       memory reporters to test whether the memory reporters are producing
+       sensible results. -->
+
+  <!-- test results are displayed in the html:body -->
+  <body xmlns="http://www.w3.org/1999/xhtml"></body>
+
+  <!-- test code goes here -->
+  <script type="application/javascript">
+  <![CDATA[
+  "use strict";
+
+  SimpleTest.expectAssertions(27);
+
+  let mgr = Cc["@mozilla.org/memory-reporter-manager;1"].
+            getService(Ci.nsIMemoryReporterManager);
+
+  // Hide all the real reporters;  we'll restore them at the end.
+  mgr.blockRegistrationAndHideExistingReporters();
+
+  // Setup various fake-but-deterministic reporters.
+  const KB = 1024;
+  const MB = KB * KB;
+  const NONHEAP = Ci.nsIMemoryReporter.KIND_NONHEAP;
+  const HEAP    = Ci.nsIMemoryReporter.KIND_HEAP;
+  const OTHER   = Ci.nsIMemoryReporter.KIND_OTHER;
+
+  const BYTES = Ci.nsIMemoryReporter.UNITS_BYTES;
+  const COUNT = Ci.nsIMemoryReporter.UNITS_COUNT;
+  const COUNT_CUMULATIVE = Ci.nsIMemoryReporter.UNITS_COUNT_CUMULATIVE;
+  const PERCENTAGE = Ci.nsIMemoryReporter.UNITS_PERCENTAGE;
+
+  let fakeReporters = [
+    { collectReports(aCbObj, aClosure, aAnonymize) {
+        function f(aP, aK, aU, aA) {
+          aCbObj.callback("Main Process", aP, aK, aU, aA, "Desc.", aClosure);
+        }
+        f("heap-allocated",     OTHER,   BYTES, 500 * MB);
+        f("heap-unallocated",   OTHER,   BYTES, 100 * MB);
+        f("explicit/a",         HEAP,    BYTES, 222 * MB);
+        f("explicit/b/a",       HEAP,    BYTES,  85 * MB);
+        f("explicit/b/b",       HEAP,    BYTES,  75 * MB);
+        f("explicit/b/c/a",     HEAP,    BYTES,  70 * MB);
+        f("explicit/b/c/b",     HEAP,    BYTES,   2 * MB); // omitted
+        f("explicit/g/a",       HEAP,    BYTES,   6 * MB);
+        f("explicit/g/b",       HEAP,    BYTES,   5 * MB);
+        f("explicit/g/other",   HEAP,    BYTES,   4 * MB);
+        // A degenerate tree with the same name as a non-degenerate tree should
+        // work ok.
+        f("explicit",           OTHER,   BYTES, 888 * MB);
+        f("other1/a/b",         OTHER,   BYTES, 111 * MB);
+        f("other1/c/d",         OTHER,   BYTES,  22 * MB);
+        f("other1/c/e",         OTHER,   BYTES,  33 * MB);
+        f("other4",             OTHER,   COUNT_CUMULATIVE, 777);
+        f("other4",             OTHER,   COUNT_CUMULATIVE, 111);
+        f("other3/a/b/c/d/e",   OTHER,   PERCENTAGE, 2000);
+        f("other3/a/b/c/d/f",   OTHER,   PERCENTAGE, 10);
+        f("other3/a/b/c/d/g",   OTHER,   PERCENTAGE, 5);
+        f("other3/a/b/c/d/g",   OTHER,   PERCENTAGE, 5);
+        // Check that a rounded-up-to-100.00% value is shown as "100.0%" (i.e. one
+        // decimal point).
+        f("other6/big",         OTHER,   COUNT, 99999);
+        f("other6/small",       OTHER,   COUNT, 1);
+        // Check that a 0 / 0 is handled correctly.
+        f("other7/zero",        OTHER,   BYTES, 0);
+        // These compartments ones shouldn't be displayed.
+        f("compartments/user/foo",   OTHER, COUNT, 1);
+        f("compartments/system/foo", OTHER, COUNT, 1);
+      }
+    },
+    { collectReports(aCbObj, aClosure, aAnonymize) {
+        function f(aP, aK, aU, aA) {
+          aCbObj.callback("Main Process", aP, aK, aU, aA, "Desc.", aClosure);
+        }
+        f("explicit/c/d",     NONHEAP, BYTES,  13 * MB);
+        f("explicit/c/d",     NONHEAP, BYTES,  10 * MB); // dup
+        f("explicit/c/other", NONHEAP, BYTES,  77 * MB);
+        f("explicit/cc",      NONHEAP, BYTES,  13 * MB);
+        f("explicit/cc",      NONHEAP, BYTES,  10 * MB); // dup
+        f("explicit/d",       NONHEAP, BYTES, 499 * KB); // omitted
+        f("explicit/e",       NONHEAP, BYTES, 100 * KB); // omitted
+        f("explicit/f/g/h/i", HEAP,    BYTES,  10 * MB);
+        f("explicit/f/g/h/j", HEAP,    BYTES,  10 * MB);
+      }
+    },
+    { collectReports(aCbObj, aClosure, aAnonymize) {
+        function f(aP, aK, aU, aA) {
+          aCbObj.callback("Main Process", aP, aK, aU, aA, "Desc.", aClosure);
+        }
+        f("other3",           OTHER,   COUNT, 777);
+        f("other2",           OTHER,   BYTES, 222 * MB);
+        f("perc2",            OTHER,   PERCENTAGE, 10000);
+        f("perc1",            OTHER,   PERCENTAGE, 4567);
+        f("compartments/user/https:\\\\very-long-url.com\\very-long\\oh-so-long\\really-quite-long.html?a=2&b=3&c=4&d=5&e=abcdefghijklmnopqrstuvwxyz&f=123456789123456789123456789", OTHER, COUNT, 1);
+      }
+    },
+    { collectReports(aCbObj, aClosure, aAnonymize) {
+        function f(aP) {
+          aCbObj.callback("Main Process", aP, OTHER, COUNT, 1, "Desc.", aClosure);
+        }
+        f("compartments/user/bar");
+        f("compartments/system/bar");
+      }
+    }
+  ];
+  for (let i = 0; i < fakeReporters.length; i++) {
+    mgr.registerStrongReporterEvenIfBlocked(fakeReporters[i]);
+  }
+
+  // The main process always comes first when we display about:memory.  The
+  // remaining processes are sorted by their |resident| values (starting with
+  // the largest).  Processes without a |resident| memory reporter are saved
+  // for the end.
+  let fakeReporters2 = [
+    { collectReports(aCbObj, aClosure, aAnonymize) {
+        function f(aP1, aP2, aK, aU, aA) {
+          aCbObj.callback(aP1, aP2, aK, aU, aA, "Desc.", aClosure);
+        }
+        f("2nd", "heap-allocated",  OTHER,   BYTES,1000* MB);
+        f("2nd", "heap-unallocated",OTHER,   BYTES,100 * MB);
+        f("2nd", "explicit/a/b/c",  HEAP,    BYTES,497 * MB);
+        f("2nd", "explicit/a/b/c",  HEAP,    BYTES,  1 * MB); // dup: merge
+        f("2nd", "explicit/a/b/c",  HEAP,    BYTES,  1 * MB); // dup: merge
+        f("2nd", "explicit/flip\\the\\backslashes",
+                                    HEAP,    BYTES,200 * MB);
+        f("2nd", "explicit/compartment(compartment-url)",
+                                    HEAP,    BYTES,200 * MB);
+        f("2nd", "other0",          OTHER,   BYTES,666 * MB);
+        f("2nd", "other1",          OTHER,   BYTES,111 * MB);
+
+        // Check that we can handle "heap-allocated" not being present.
+        f("3rd", "explicit/a/b",    HEAP,    BYTES,333 * MB);
+        f("3rd", "explicit/a/c",    HEAP,    BYTES,444 * MB);
+        f("3rd", "other1",          OTHER,   BYTES,  1 * MB);
+        f("3rd", "resident",        OTHER,   BYTES,100 * MB);
+
+        // Invalid values (negative, too-big) should be identified.
+        f("4th", "heap-allocated",   OTHER,   BYTES,100 * MB);
+        f("4th", "resident",         OTHER,   BYTES,200 * MB);
+        f("4th", "explicit/js/compartment(http:\\\\too-big.com\\)/stuff",
+                                     HEAP,    BYTES,150 * MB);
+        f("4th", "explicit/ok",      HEAP,    BYTES,  5 * MB);
+        f("4th", "explicit/neg1",    NONHEAP, BYTES, -2 * MB);
+        // -111 becomes "-0.00MB" in non-verbose mode, and getting the negative
+        // sign in there correctly is non-trivial.
+        f("4th",  "other1",          OTHER,   BYTES,-111);
+        f("4th",  "other2",          OTHER,   BYTES,-222 * MB);
+        f("4th",  "other3",          OTHER,   COUNT, -333);
+        f("4th",  "other4",          OTHER,   COUNT_CUMULATIVE, -444);
+        f("4th",  "other5",          OTHER,   PERCENTAGE, -555);
+        f("4th",  "other6",          OTHER,   PERCENTAGE, 66666);
+
+        // If a negative value is within a collapsed sub-tree in non-verbose mode,
+        // we should get the warning at the top and the relevant sub-trees should
+        // be expanded, even in non-verbose mode.
+        f("5th", "heap-allocated",   OTHER,   BYTES,100 * MB);
+        f("5th", "explicit/big",     HEAP,    BYTES, 99 * MB);
+        f("5th", "explicit/a/pos",   HEAP,    BYTES, 40 * KB);
+        f("5th", "explicit/a/neg1",  NONHEAP, BYTES,-20 * KB);
+        f("5th", "explicit/a/neg2",  NONHEAP, BYTES,-10 * KB);
+        f("5th", "explicit/b/c/d/e", NONHEAP, BYTES, 20 * KB);
+        f("5th", "explicit/b/c/d/f", NONHEAP, BYTES,-60 * KB);
+        f("5th", "explicit/b/c/g/h", NONHEAP, BYTES, 10 * KB);
+        f("5th", "explicit/b/c/i/j", NONHEAP, BYTES,  5 * KB);
+      }
+    }
+  ];
+  for (let i = 0; i < fakeReporters2.length; i++) {
+    mgr.registerStrongReporterEvenIfBlocked(fakeReporters2[i]);
+  }
+  fakeReporters = fakeReporters.concat(fakeReporters2);
+  ]]>
+  </script>
+
+  <iframe id="amFrame"  height="300" src="about:memory"></iframe>
+  <!-- vary the capitalization to make sure that works -->
+  <iframe id="amvFrame" height="300" src="About:Memory"></iframe>
+
+  <script type="application/javascript">
+  <![CDATA[
+  let amExpectedText =
+"\
+Main Process\n\
+Explicit Allocations\n\
+\n\
+623.58 MB (100.0%) -- explicit\n\
+├──232.00 MB (37.20%) -- b\n\
+│  ├───85.00 MB (13.63%) ── a\n\
+│  ├───75.00 MB (12.03%) ── b\n\
+│  └───72.00 MB (11.55%) -- c\n\
+│      ├──70.00 MB (11.23%) ── a\n\
+│      └───2.00 MB (00.32%) ── b\n\
+├──222.00 MB (35.60%) ── a\n\
+├──100.00 MB (16.04%) -- c\n\
+│  ├───77.00 MB (12.35%) ── other\n\
+│  └───23.00 MB (03.69%) ── d [2]\n\
+├───23.00 MB (03.69%) ── cc [2]\n\
+├───20.00 MB (03.21%) -- f/g/h\n\
+│   ├──10.00 MB (01.60%) ── i\n\
+│   └──10.00 MB (01.60%) ── j\n\
+├───15.00 MB (02.41%) ++ g\n\
+├───11.00 MB (01.76%) ── heap-unclassified\n\
+└────0.58 MB (00.09%) ++ (2 tiny)\n\
+\n\
+Other Measurements\n\
+\n\
+5 (100.0%) -- compartments\n\
+├──3 (60.00%) -- user\n\
+│  ├──1 (20.00%) ── bar\n\
+│  ├──1 (20.00%) ── foo\n\
+│  └──1 (20.00%) ── https://very-long-url.com/very-long/oh-so-long/really-quite-long.html?a=2&b=3&c=4&d=5&e=abcdefghijklmnopqrstuvwxyz&f=123456789123456789123456789\n\
+└──2 (40.00%) -- system\n\
+   ├──1 (20.00%) ── bar\n\
+   └──1 (20.00%) ── foo\n\
+\n\
+166.00 MB (100.0%) -- other1\n\
+├──111.00 MB (66.87%) ── a/b\n\
+└───55.00 MB (33.13%) -- c\n\
+    ├──33.00 MB (19.88%) ── e\n\
+    └──22.00 MB (13.25%) ── d\n\
+\n\
+20.20% (100.0%) -- other3\n\
+└──20.20% (100.0%) -- a/b/c/d\n\
+   ├──20.00% (99.01%) ── e\n\
+   └───0.20% (00.99%) ++ (2 tiny)\n\
+\n\
+100,000 (100.0%) -- other6\n\
+├───99,999 (100.0%) ── big\n\
+└────────1 (00.00%) ── small\n\
+\n\
+0.00 MB (100.0%) -- other7\n\
+└──0.00 MB (100.0%) ── zero\n\
+\n\
+888.00 MB ── explicit\n\
+500.00 MB ── heap-allocated\n\
+100.00 MB ── heap-unallocated\n\
+222.00 MB ── other2\n\
+      777 ── other3\n\
+      888 ── other4 [2]\n\
+   45.67% ── perc1\n\
+  100.00% ── perc2\n\
+\n\
+End of Main Process\n\
+4th\n\
+\n\
+WARNING: the following values are negative or unreasonably large.\n\
+\n\
+    explicit/js/compartment(http://too-big.com/)/stuff\n\
+    explicit/(2 tiny)\n\
+    explicit/(2 tiny)/neg1\n\
+    explicit/(2 tiny)/heap-unclassified\n\
+    other1\n\
+    other2\n\
+    other3\n\
+    other4\n\
+    other5 \n\
+\n\
+This indicates a defect in one or more memory reporters. The invalid values are highlighted.\n\
+Explicit Allocations\n\
+\n\
+98.00 MB (100.0%) -- explicit\n\
+├──150.00 MB (153.06%) ── js/compartment(http://too-big.com/)/stuff [?!]\n\
+├───5.00 MB (05.10%) ── ok\n\
+└──-57.00 MB (-58.16%) -- (2 tiny) [?!]\n\
+   ├───-2.00 MB (-02.04%) ── neg1 [?!]\n\
+   └──-55.00 MB (-56.12%) ── heap-unclassified [?!]\n\
+\n\
+Other Measurements\n\
+\n\
+ 100.00 MB ── heap-allocated\n\
+  -0.00 MB ── other1 [?!]\n\
+-222.00 MB ── other2 [?!]\n\
+      -333 ── other3 [?!]\n\
+      -444 ── other4 [?!]\n\
+    -5.55% ── other5 [?!]\n\
+   666.66% ── other6\n\
+ 200.00 MB ── resident\n\
+\n\
+End of 4th\n\
+3rd\n\
+\n\
+WARNING: the 'heap-allocated' memory reporter does not work for this platform and/or configuration. This means that 'heap-unclassified' is not shown and the 'explicit' tree shows less memory than it should.\n\
+Explicit Allocations\n\
+\n\
+777.00 MB (100.0%) -- explicit\n\
+└──777.00 MB (100.0%) -- a\n\
+   ├──444.00 MB (57.14%) ── c\n\
+   └──333.00 MB (42.86%) ── b\n\
+\n\
+Other Measurements\n\
+\n\
+  1.00 MB ── other1\n\
+100.00 MB ── resident\n\
+\n\
+End of 3rd\n\
+2nd\n\
+Explicit Allocations\n\
+\n\
+1,000.00 MB (100.0%) -- explicit\n\
+├────499.00 MB (49.90%) ── a/b/c [3]\n\
+├────200.00 MB (20.00%) ── compartment(compartment-url)\n\
+├────200.00 MB (20.00%) ── flip/the/backslashes\n\
+└────101.00 MB (10.10%) ── heap-unclassified\n\
+\n\
+Other Measurements\n\
+\n\
+1,000.00 MB ── heap-allocated\n\
+  100.00 MB ── heap-unallocated\n\
+  666.00 MB ── other0\n\
+  111.00 MB ── other1\n\
+\n\
+End of 2nd\n\
+5th\n\
+\n\
+WARNING: the following values are negative or unreasonably large.\n\
+\n\
+    explicit/(3 tiny)/a/neg2\n\
+    explicit/(3 tiny)/a/neg1\n\
+    explicit/(3 tiny)/b/c\n\
+    explicit/(3 tiny)/b/c/d\n\
+    explicit/(3 tiny)/b/c/d/f \n\
+\n\
+This indicates a defect in one or more memory reporters. The invalid values are highlighted.\n\
+Explicit Allocations\n\
+\n\
+99.95 MB (100.0%) -- explicit\n\
+├──99.00 MB (99.05%) ── big\n\
+└───0.95 MB (00.95%) -- (3 tiny)\n\
+    ├──0.96 MB (00.96%) ── heap-unclassified\n\
+    ├──0.01 MB (00.01%) -- a\n\
+    │  ├──0.04 MB (00.04%) ── pos\n\
+    │  ├──-0.01 MB (-00.01%) ── neg2 [?!]\n\
+    │  └──-0.02 MB (-00.02%) ── neg1 [?!]\n\
+    └──-0.02 MB (-00.02%) -- b/c [?!]\n\
+       ├───0.01 MB (00.01%) ── g/h\n\
+       ├───0.00 MB (00.00%) ── i/j\n\
+       └──-0.04 MB (-00.04%) -- d [?!]\n\
+          ├───0.02 MB (00.02%) ── e\n\
+          └──-0.06 MB (-00.06%) ── f [?!]\n\
+\n\
+Other Measurements\n\
+\n\
+100.00 MB ── heap-allocated\n\
+\n\
+End of 5th\n\
+";
+
+  let amvExpectedText =
+"\
+Main Process\n\
+Explicit Allocations\n\
+\n\
+653,876,224 B (100.0%) -- explicit\n\
+├──243,269,632 B (37.20%) -- b\n\
+│  ├───89,128,960 B (13.63%) ── a\n\
+│  ├───78,643,200 B (12.03%) ── b\n\
+│  └───75,497,472 B (11.55%) -- c\n\
+│      ├──73,400,320 B (11.23%) ── a\n\
+│      └───2,097,152 B (00.32%) ── b\n\
+├──232,783,872 B (35.60%) ── a\n\
+├──104,857,600 B (16.04%) -- c\n\
+│  ├───80,740,352 B (12.35%) ── other\n\
+│  └───24,117,248 B (03.69%) ── d [2]\n\
+├───24,117,248 B (03.69%) ── cc [2]\n\
+├───20,971,520 B (03.21%) -- f/g/h\n\
+│   ├──10,485,760 B (01.60%) ── i\n\
+│   └──10,485,760 B (01.60%) ── j\n\
+├───15,728,640 B (02.41%) -- g\n\
+│   ├───6,291,456 B (00.96%) ── a\n\
+│   ├───5,242,880 B (00.80%) ── b\n\
+│   └───4,194,304 B (00.64%) ── other\n\
+├───11,534,336 B (01.76%) ── heap-unclassified\n\
+├──────510,976 B (00.08%) ── d\n\
+└──────102,400 B (00.02%) ── e\n\
+\n\
+Other Measurements\n\
+\n\
+5 (100.0%) -- compartments\n\
+├──3 (60.00%) -- user\n\
+│  ├──1 (20.00%) ── bar\n\
+│  ├──1 (20.00%) ── foo\n\
+│  └──1 (20.00%) ── https://very-long-url.com/very-long/oh-so-long/really-quite-long.html?a=2&b=3&c=4&d=5&e=abcdefghijklmnopqrstuvwxyz&f=123456789123456789123456789\n\
+└──2 (40.00%) -- system\n\
+   ├──1 (20.00%) ── bar\n\
+   └──1 (20.00%) ── foo\n\
+\n\
+174,063,616 B (100.0%) -- other1\n\
+├──116,391,936 B (66.87%) ── a/b\n\
+└───57,671,680 B (33.13%) -- c\n\
+    ├──34,603,008 B (19.88%) ── e\n\
+    └──23,068,672 B (13.25%) ── d\n\
+\n\
+20.20% (100.0%) -- other3\n\
+└──20.20% (100.0%) -- a/b/c/d\n\
+   ├──20.00% (99.01%) ── e\n\
+   ├───0.10% (00.50%) ── f\n\
+   └───0.10% (00.50%) ── g [2]\n\
+\n\
+100,000 (100.0%) -- other6\n\
+├───99,999 (100.0%) ── big\n\
+└────────1 (00.00%) ── small\n\
+\n\
+0 B (100.0%) -- other7\n\
+└──0 B (100.0%) ── zero\n\
+\n\
+931,135,488 B ── explicit\n\
+524,288,000 B ── heap-allocated\n\
+104,857,600 B ── heap-unallocated\n\
+232,783,872 B ── other2\n\
+          777 ── other3\n\
+          888 ── other4 [2]\n\
+       45.67% ── perc1\n\
+      100.00% ── perc2\n\
+\n\
+End of Main Process\n\
+4th\n\
+\n\
+WARNING: the following values are negative or unreasonably large.\n\
+\n\
+    explicit/js/compartment(http://too-big.com/)/stuff\n\
+    explicit/neg1\n\
+    explicit/heap-unclassified\n\
+    other1\n\
+    other2\n\
+    other3\n\
+    other4\n\
+    other5 \n\
+\n\
+This indicates a defect in one or more memory reporters. The invalid values are highlighted.\n\
+Explicit Allocations\n\
+\n\
+102,760,448 B (100.0%) -- explicit\n\
+├──157,286,400 B (153.06%) ── js/compartment(http://too-big.com/)/stuff [?!]\n\
+├────5,242,880 B (05.10%) ── ok\n\
+├───-2,097,152 B (-02.04%) ── neg1 [?!]\n\
+└──-57,671,680 B (-56.12%) ── heap-unclassified [?!]\n\
+\n\
+Other Measurements\n\
+\n\
+ 104,857,600 B ── heap-allocated\n\
+        -111 B ── other1 [?!]\n\
+-232,783,872 B ── other2 [?!]\n\
+          -333 ── other3 [?!]\n\
+          -444 ── other4 [?!]\n\
+        -5.55% ── other5 [?!]\n\
+       666.66% ── other6\n\
+ 209,715,200 B ── resident\n\
+\n\
+End of 4th\n\
+3rd\n\
+\n\
+WARNING: the 'heap-allocated' memory reporter does not work for this platform and/or configuration. This means that 'heap-unclassified' is not shown and the 'explicit' tree shows less memory than it should.\n\
+Explicit Allocations\n\
+\n\
+814,743,552 B (100.0%) -- explicit\n\
+└──814,743,552 B (100.0%) -- a\n\
+   ├──465,567,744 B (57.14%) ── c\n\
+   └──349,175,808 B (42.86%) ── b\n\
+\n\
+Other Measurements\n\
+\n\
+  1,048,576 B ── other1\n\
+104,857,600 B ── resident\n\
+\n\
+End of 3rd\n\
+2nd\n\
+Explicit Allocations\n\
+\n\
+1,048,576,000 B (100.0%) -- explicit\n\
+├────523,239,424 B (49.90%) ── a/b/c [3]\n\
+├────209,715,200 B (20.00%) ── compartment(compartment-url)\n\
+├────209,715,200 B (20.00%) ── flip/the/backslashes\n\
+└────105,906,176 B (10.10%) ── heap-unclassified\n\
+\n\
+Other Measurements\n\
+\n\
+1,048,576,000 B ── heap-allocated\n\
+  104,857,600 B ── heap-unallocated\n\
+  698,351,616 B ── other0\n\
+  116,391,936 B ── other1\n\
+\n\
+End of 2nd\n\
+5th\n\
+\n\
+WARNING: the following values are negative or unreasonably large.\n\
+\n\
+    explicit/a/neg2\n\
+    explicit/a/neg1\n\
+    explicit/b/c\n\
+    explicit/b/c/d\n\
+    explicit/b/c/d/f \n\
+\n\
+This indicates a defect in one or more memory reporters. The invalid values are highlighted.\n\
+Explicit Allocations\n\
+\n\
+104,801,280 B (100.0%) -- explicit\n\
+├──103,809,024 B (99.05%) ── big\n\
+├────1,007,616 B (00.96%) ── heap-unclassified\n\
+├───────10,240 B (00.01%) -- a\n\
+│       ├──40,960 B (00.04%) ── pos\n\
+│       ├──-10,240 B (-00.01%) ── neg2 [?!]\n\
+│       └──-20,480 B (-00.02%) ── neg1 [?!]\n\
+└──────-25,600 B (-00.02%) -- b/c [?!]\n\
+       ├───10,240 B (00.01%) ── g/h\n\
+       ├────5,120 B (00.00%) ── i/j\n\
+       └──-40,960 B (-00.04%) -- d [?!]\n\
+          ├───20,480 B (00.02%) ── e\n\
+          └──-61,440 B (-00.06%) ── f [?!]\n\
+\n\
+Other Measurements\n\
+\n\
+104,857,600 B ── heap-allocated\n\
+\n\
+End of 5th\n\
+";
+
+  function finish()
+  {
+    mgr.unblockRegistrationAndRestoreOriginalReporters();
+    SimpleTest.finish();
+  }
+
+  // Cut+paste the entire page and check that the cut text matches what we
+  // expect.  This tests the output in general and also that the cutting and
+  // pasting works as expected.
+  function test(aFrameId, aVerbose, aExpected, aNext) {
+    SimpleTest.executeSoon(function() {
+      ok(document.title === "about:memory", "document.title is correct");
+      let mostRecentActual;
+      let frame = document.getElementById(aFrameId);
+      frame.focus();
+
+      // Set the verbose checkbox value and click the go button.
+      let doc = frame.contentWindow.document;
+      let measureButton = doc.getElementById("measureButton");
+      let verbose = doc.getElementById("verbose");
+      verbose.checked = aVerbose;
+      measureButton.click();
+
+      SimpleTest.waitForClipboard(
+        function(aActual) {
+          mostRecentActual = aActual;
+          let rslt = aActual.trim() === aExpected.trim();
+          if (!rslt) {
+            // Try copying again.
+            synthesizeKey("A", {accelKey: true});
+            synthesizeKey("C", {accelKey: true});
+          }
+
+          return rslt;
+        },
+        function() {
+          synthesizeKey("A", {accelKey: true});
+          synthesizeKey("C", {accelKey: true});
+        },
+        aNext,
+        function() {
+          ok(false, "pasted text doesn't match for " + aFrameId);
+          dump("******EXPECTED******\n");
+          dump("<<<" + aExpected + ">>>\n");
+          dump("*******ACTUAL*******\n");
+          dump("<<<" + mostRecentActual + ">>>\n");
+          dump("********************\n");
+          finish();
+        }
+      );
+    });
+  }
+
+  SimpleTest.waitForFocus(function() {
+    test(
+      "amFrame",
+      /* verbose = */ false,
+      amExpectedText,
+      function() {
+        test(
+          "amvFrame",
+          /* verbose = */ true,
+          amvExpectedText,
+          function() {
+            finish()
+          }
+        )
+      }
+    );
+  });
+  SimpleTest.waitForExplicitFinish();
+  ]]>
+  </script>
+</window>
diff --git a/toolkit/components/aboutmemory/tests/test_aboutmemory2.xhtml b/toolkit/components/aboutmemory/tests/test_aboutmemory2.xhtml
new file mode 100644
index 0000000000..28c8f7fa4f
--- /dev/null
+++ b/toolkit/components/aboutmemory/tests/test_aboutmemory2.xhtml
@@ -0,0 +1,420 @@
+<?xml version="1.0"?>
+<?xml-stylesheet type="text/css" href="chrome://global/skin"?>
+<?xml-stylesheet type="text/css" href="chrome://mochikit/content/tests/SimpleTest/test.css"?>
+<window title="about:memory"
+        xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul">
+  <script src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"/>
+  <script src="chrome://mochikit/content/tests/SimpleTest/EventUtils.js"></script>
+
+  <!-- This file tests the collapsing and expanding of sub-trees in
+       about:memory. -->
+
+  <!-- test results are displayed in the html:body -->
+  <body xmlns="http://www.w3.org/1999/xhtml"></body>
+
+  <!-- test code goes here -->
+  <script type="application/javascript">
+  <![CDATA[
+  "use strict";
+
+  let mgr = Cc["@mozilla.org/memory-reporter-manager;1"].
+            getService(Ci.nsIMemoryReporterManager);
+
+  // Hide all the real reporters;  we'll restore them at the end.
+  mgr.blockRegistrationAndHideExistingReporters();
+
+  // Setup various fake-but-deterministic reporters.
+  const KB = 1024;
+  const MB = KB * KB;
+  const HEAP  = Ci.nsIMemoryReporter.KIND_HEAP;
+  const OTHER = Ci.nsIMemoryReporter.KIND_OTHER;
+  const BYTES = Ci.nsIMemoryReporter.UNITS_BYTES;
+
+  let hiPath  = "explicit/h/i";
+  let hi2Path = "explicit/h/i2";
+  let jkPath  = "explicit/j/k";
+  let jk2Path = "explicit/j/k2";
+
+  let fakeReporters = [
+    { collectReports(aCbObj, aClosure, aAnonymize) {
+        function f(aP, aK, aA) {
+          aCbObj.callback("Main Process ABC", aP, aK, BYTES, aA, "Desc.", aClosure);
+        }
+        f("heap-allocated",     OTHER,   250 * MB);
+        f("explicit/a/b",       HEAP,     50 * MB);
+        f("explicit/a/c/d",     HEAP,     25 * MB);
+        f("explicit/a/c/e",     HEAP,     15 * MB);
+        f("explicit/a/f",       HEAP,     30 * MB);
+        f("explicit/g",         HEAP,    100 * MB);
+        f(hiPath,               HEAP,     10 * MB);
+        f(hi2Path,              HEAP,      9 * MB);
+        f(jkPath,               HEAP,    0.5 * MB);
+        f(jk2Path,              HEAP,    0.3 * MB);
+        f("explicit/a/l/m",     HEAP,    0.1 * MB);
+        f("explicit/a/l/n",     HEAP,    0.1 * MB);
+      }
+    }
+  ];
+
+  for (let i = 0; i < fakeReporters.length; i++) {
+    mgr.registerStrongReporterEvenIfBlocked(fakeReporters[i]);
+  }
+
+  ]]>
+  </script>
+
+  <iframe id="amFrame"  height="500" src="about:memory"></iframe>
+
+  <script type="application/javascript">
+  <![CDATA[
+  function finish()
+  {
+    mgr.unblockRegistrationAndRestoreOriginalReporters();
+    SimpleTest.finish();
+  }
+
+  // Click on the identified element, then cut+paste the entire page and
+  // check that the cut text matches what we expect.
+  function test(aId, aSwap, aExpected, aNext) {
+    let win = document.getElementById("amFrame").contentWindow;
+    if (aId) {
+      let node = win.document.getElementById(aId);
+
+      // Yuk:  clicking a button is easy;  but for tree entries we need to
+      // click on a child of the span identified via |id|.
+      if (node.nodeName === "button") {
+        if (aSwap) {
+          // We swap hipath/hi2Path and jkPath/jk2Path just before updating, to
+          // test what happens when significant nodes become insignificant and
+          // vice versa.
+          hiPath  = "explicit/j/k";
+          hi2Path = "explicit/j/k2";
+          jkPath  = "explicit/h/i";
+          jk2Path = "explicit/h/i2";
+        }
+        node.click();
+      } else {
+        node.childNodes[0].click();
+      }
+    }
+
+    SimpleTest.executeSoon(function() {
+      let mostRecentActual;
+      document.getElementById("amFrame").focus();
+      SimpleTest.waitForClipboard(
+        function(aActual) {
+          mostRecentActual = aActual;
+          let rslt = aActual.trim() === aExpected.trim();
+          if (!rslt) {
+            // Try copying again.
+            synthesizeKey("A", {accelKey: true});
+            synthesizeKey("C", {accelKey: true});
+          }
+
+          return rslt;
+        },
+        function() {
+          synthesizeKey("A", {accelKey: true});
+          synthesizeKey("C", {accelKey: true});
+        },
+        aNext,
+        function() {
+          ok(false, "pasted text doesn't match");
+          dump("******EXPECTED******\n");
+          dump(aExpected);
+          dump("*******ACTUAL*******\n");
+          dump(mostRecentActual);
+          dump("********************\n");
+          finish();
+        }
+      );
+    });
+  }
+
+  // Returns a function that chains together one test() call per id.
+  function chain(aIds) {
+    let x = aIds.shift();
+    if (x) {
+      return function() { test(x.id, x.swap, x.expected, chain(aIds)); }
+    }
+    return function() { finish(); };
+  }
+
+  let startExpected =
+"\
+Main Process ABC\n\
+Explicit Allocations\n\
+\n\
+250.00 MB (100.0%) -- explicit\n\
+├──120.20 MB (48.08%) -- a\n\
+│  ├───50.00 MB (20.00%) ── b\n\
+│  ├───40.00 MB (16.00%) -- c\n\
+│  │   ├──25.00 MB (10.00%) ── d\n\
+│  │   └──15.00 MB (06.00%) ── e\n\
+│  ├───30.00 MB (12.00%) ── f\n\
+│  └────0.20 MB (00.08%) ++ l\n\
+├──100.00 MB (40.00%) ── g\n\
+├───19.00 MB (07.60%) -- h\n\
+│   ├──10.00 MB (04.00%) ── i\n\
+│   └───9.00 MB (03.60%) ── i2\n\
+├───10.00 MB (04.00%) ── heap-unclassified\n\
+└────0.80 MB (00.32%) ++ j\n\
+\n\
+Other Measurements\n\
+\n\
+250.00 MB ── heap-allocated\n\
+\n\
+End of Main Process ABC\n\
+";
+
+  let acCollapsedExpected =
+"\
+Main Process ABC\n\
+Explicit Allocations\n\
+\n\
+250.00 MB (100.0%) -- explicit\n\
+├──120.20 MB (48.08%) -- a\n\
+│  ├───50.00 MB (20.00%) ── b\n\
+│  ├───40.00 MB (16.00%) ++ c\n\
+│  ├───30.00 MB (12.00%) ── f\n\
+│  └────0.20 MB (00.08%) ++ l\n\
+├──100.00 MB (40.00%) ── g\n\
+├───19.00 MB (07.60%) -- h\n\
+│   ├──10.00 MB (04.00%) ── i\n\
+│   └───9.00 MB (03.60%) ── i2\n\
+├───10.00 MB (04.00%) ── heap-unclassified\n\
+└────0.80 MB (00.32%) ++ j\n\
+\n\
+Other Measurements\n\
+\n\
+250.00 MB ── heap-allocated\n\
+\n\
+End of Main Process ABC\n\
+";
+
+  let alExpandedExpected =
+"\
+Main Process ABC\n\
+Explicit Allocations\n\
+\n\
+250.00 MB (100.0%) -- explicit\n\
+├──120.20 MB (48.08%) -- a\n\
+│  ├───50.00 MB (20.00%) ── b\n\
+│  ├───40.00 MB (16.00%) ++ c\n\
+│  ├───30.00 MB (12.00%) ── f\n\
+│  └────0.20 MB (00.08%) -- l\n\
+│       ├──0.10 MB (00.04%) ── m\n\
+│       └──0.10 MB (00.04%) ── n\n\
+├──100.00 MB (40.00%) ── g\n\
+├───19.00 MB (07.60%) -- h\n\
+│   ├──10.00 MB (04.00%) ── i\n\
+│   └───9.00 MB (03.60%) ── i2\n\
+├───10.00 MB (04.00%) ── heap-unclassified\n\
+└────0.80 MB (00.32%) ++ j\n\
+\n\
+Other Measurements\n\
+\n\
+250.00 MB ── heap-allocated\n\
+\n\
+End of Main Process ABC\n\
+";
+
+  let aCollapsedExpected =
+"\
+Main Process ABC\n\
+Explicit Allocations\n\
+\n\
+250.00 MB (100.0%) -- explicit\n\
+├──120.20 MB (48.08%) ++ a\n\
+├──100.00 MB (40.00%) ── g\n\
+├───19.00 MB (07.60%) -- h\n\
+│   ├──10.00 MB (04.00%) ── i\n\
+│   └───9.00 MB (03.60%) ── i2\n\
+├───10.00 MB (04.00%) ── heap-unclassified\n\
+└────0.80 MB (00.32%) ++ j\n\
+\n\
+Other Measurements\n\
+\n\
+250.00 MB ── heap-allocated\n\
+\n\
+End of Main Process ABC\n\
+";
+
+  let hCollapsedExpected =
+"\
+Main Process ABC\n\
+Explicit Allocations\n\
+\n\
+250.00 MB (100.0%) -- explicit\n\
+├──120.20 MB (48.08%) ++ a\n\
+├──100.00 MB (40.00%) ── g\n\
+├───19.00 MB (07.60%) ++ h\n\
+├───10.00 MB (04.00%) ── heap-unclassified\n\
+└────0.80 MB (00.32%) ++ j\n\
+\n\
+Other Measurements\n\
+\n\
+250.00 MB ── heap-allocated\n\
+\n\
+End of Main Process ABC\n\
+";
+
+  let jExpandedExpected =
+"\
+Main Process ABC\n\
+Explicit Allocations\n\
+\n\
+250.00 MB (100.0%) -- explicit\n\
+├──120.20 MB (48.08%) ++ a\n\
+├──100.00 MB (40.00%) ── g\n\
+├───19.00 MB (07.60%) ++ h\n\
+├───10.00 MB (04.00%) ── heap-unclassified\n\
+└────0.80 MB (00.32%) -- j\n\
+     ├──0.50 MB (00.20%) ── k\n\
+     └──0.30 MB (00.12%) ── k2\n\
+\n\
+Other Measurements\n\
+\n\
+250.00 MB ── heap-allocated\n\
+\n\
+End of Main Process ABC\n\
+";
+
+  // The important thing here is that two values have been swapped.
+  // explicit/h/i should remain collapsed, and explicit/j/k should remain
+  // expanded.  See bug 724863.
+  let updatedExpected =
+"\
+Main Process ABC\n\
+Explicit Allocations\n\
+\n\
+250.00 MB (100.0%) -- explicit\n\
+├──120.20 MB (48.08%) ++ a\n\
+├──100.00 MB (40.00%) ── g\n\
+├───19.00 MB (07.60%) -- j\n\
+│   ├──10.00 MB (04.00%) ── k\n\
+│   └───9.00 MB (03.60%) ── k2\n\
+├───10.00 MB (04.00%) ── heap-unclassified\n\
+└────0.80 MB (00.32%) ++ h\n\
+\n\
+Other Measurements\n\
+\n\
+250.00 MB ── heap-allocated\n\
+\n\
+End of Main Process ABC\n\
+";
+
+  let aExpandedExpected =
+"\
+Main Process ABC\n\
+Explicit Allocations\n\
+\n\
+250.00 MB (100.0%) -- explicit\n\
+├──120.20 MB (48.08%) -- a\n\
+│  ├───50.00 MB (20.00%) ── b\n\
+│  ├───40.00 MB (16.00%) ++ c\n\
+│  ├───30.00 MB (12.00%) ── f\n\
+│  └────0.20 MB (00.08%) -- l\n\
+│       ├──0.10 MB (00.04%) ── m\n\
+│       └──0.10 MB (00.04%) ── n\n\
+├──100.00 MB (40.00%) ── g\n\
+├───19.00 MB (07.60%) -- j\n\
+│   ├──10.00 MB (04.00%) ── k\n\
+│   └───9.00 MB (03.60%) ── k2\n\
+├───10.00 MB (04.00%) ── heap-unclassified\n\
+└────0.80 MB (00.32%) ++ h\n\
+\n\
+Other Measurements\n\
+\n\
+250.00 MB ── heap-allocated\n\
+\n\
+End of Main Process ABC\n\
+";
+
+  let acExpandedExpected =
+"\
+Main Process ABC\n\
+Explicit Allocations\n\
+\n\
+250.00 MB (100.0%) -- explicit\n\
+├──120.20 MB (48.08%) -- a\n\
+│  ├───50.00 MB (20.00%) ── b\n\
+│  ├───40.00 MB (16.00%) -- c\n\
+│  │   ├──25.00 MB (10.00%) ── d\n\
+│  │   └──15.00 MB (06.00%) ── e\n\
+│  ├───30.00 MB (12.00%) ── f\n\
+│  └────0.20 MB (00.08%) -- l\n\
+│       ├──0.10 MB (00.04%) ── m\n\
+│       └──0.10 MB (00.04%) ── n\n\
+├──100.00 MB (40.00%) ── g\n\
+├───19.00 MB (07.60%) -- j\n\
+│   ├──10.00 MB (04.00%) ── k\n\
+│   └───9.00 MB (03.60%) ── k2\n\
+├───10.00 MB (04.00%) ── heap-unclassified\n\
+└────0.80 MB (00.32%) ++ h\n\
+\n\
+Other Measurements\n\
+\n\
+250.00 MB ── heap-allocated\n\
+\n\
+End of Main Process ABC\n\
+";
+
+  let alCollapsedExpected =
+"\
+Main Process ABC\n\
+Explicit Allocations\n\
+\n\
+250.00 MB (100.0%) -- explicit\n\
+├──120.20 MB (48.08%) -- a\n\
+│  ├───50.00 MB (20.00%) ── b\n\
+│  ├───40.00 MB (16.00%) -- c\n\
+│  │   ├──25.00 MB (10.00%) ── d\n\
+│  │   └──15.00 MB (06.00%) ── e\n\
+│  ├───30.00 MB (12.00%) ── f\n\
+│  └────0.20 MB (00.08%) ++ l\n\
+├──100.00 MB (40.00%) ── g\n\
+├───19.00 MB (07.60%) -- j\n\
+│   ├──10.00 MB (04.00%) ── k\n\
+│   └───9.00 MB (03.60%) ── k2\n\
+├───10.00 MB (04.00%) ── heap-unclassified\n\
+└────0.80 MB (00.32%) ++ h\n\
+\n\
+Other Measurements\n\
+\n\
+250.00 MB ── heap-allocated\n\
+\n\
+End of Main Process ABC\n\
+";
+
+  // Test the following cases:
+  // - explicit/a/c is significant, we collapse it, it's unchanged upon
+  //   update, we re-expand it
+  // - explicit/a/l is insignificant, we expand it, it's unchanged upon
+  //   update, we re-collapse it
+  // - explicit/a is significant, we collapse it (which hides its
+  //   sub-trees), it's unchanged upon update, we re-expand it
+  // - explicit/h is significant, we collapse it, it becomes insignificant
+  //   upon update (and should remain collapsed)
+  // - explicit/j is insignificant, we expand it, it becomes significant
+  //   upon update (and should remain expanded)
+  //
+  let idsToClick = [
+    { id: "measureButton",                 swap: 0, expected: startExpected },
+    { id: "Main Process ABC:explicit/a/c", swap: 0, expected: acCollapsedExpected },
+    { id: "Main Process ABC:explicit/a/l", swap: 0, expected: alExpandedExpected },
+    { id: "Main Process ABC:explicit/a",   swap: 0, expected: aCollapsedExpected },
+    { id: "Main Process ABC:explicit/h",   swap: 0, expected: hCollapsedExpected },
+    { id: "Main Process ABC:explicit/j",   swap: 0, expected: jExpandedExpected },
+    { id: "measureButton",                 swap: 1, expected: updatedExpected },
+    { id: "Main Process ABC:explicit/a",   swap: 0, expected: aExpandedExpected },
+    { id: "Main Process ABC:explicit/a/c", swap: 0, expected: acExpandedExpected },
+    { id: "Main Process ABC:explicit/a/l", swap: 0, expected: alCollapsedExpected }
+  ];
+
+  SimpleTest.waitForFocus(chain(idsToClick));
+
+  SimpleTest.waitForExplicitFinish();
+  ]]>
+  </script>
+</window>
diff --git a/toolkit/components/aboutmemory/tests/test_aboutmemory3.xhtml b/toolkit/components/aboutmemory/tests/test_aboutmemory3.xhtml
new file mode 100644
index 0000000000..1391af38b7
--- /dev/null
+++ b/toolkit/components/aboutmemory/tests/test_aboutmemory3.xhtml
@@ -0,0 +1,558 @@
+<?xml version="1.0"?>
+<?xml-stylesheet type="text/css" href="chrome://global/skin"?>
+<?xml-stylesheet type="text/css" href="chrome://mochikit/content/tests/SimpleTest/test.css"?>
+<window title="about:memory"
+        xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul">
+  <script src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"/>
+  <script src="chrome://mochikit/content/tests/SimpleTest/EventUtils.js"></script>
+
+  <!-- This file tests the saving and loading of memory reports to/from file in
+       about:memory. -->
+
+  <!-- test results are displayed in the html:body -->
+  <body xmlns="http://www.w3.org/1999/xhtml"></body>
+
+  <!-- test code goes here -->
+  <script type="application/javascript">
+  <![CDATA[
+  "use strict";
+
+  let mgr = Cc["@mozilla.org/memory-reporter-manager;1"].
+            getService(Ci.nsIMemoryReporterManager);
+
+  // Hide all the real reporters;  we'll restore them at the end.
+  mgr.blockRegistrationAndHideExistingReporters();
+
+  // Setup a minimal number of fake reporters.
+  const KB = 1024;
+  const MB = KB * KB;
+  const HEAP  = Ci.nsIMemoryReporter.KIND_HEAP;
+  const OTHER = Ci.nsIMemoryReporter.KIND_OTHER;
+  const BYTES = Ci.nsIMemoryReporter.UNITS_BYTES;
+
+  let fakeReporters = [
+    { collectReports(aCbObj, aClosure, aAnonymize) {
+        function f(aP, aK, aA, aD) {
+          aCbObj.callback("", aP, aK, BYTES, aA, aD, aClosure);
+        }
+        f("heap-allocated",     OTHER,   250 * MB, "Heap allocated.");
+        f("explicit/a/b",       HEAP,     50 * MB, "A b.");
+        f("other/a",            OTHER,   0.2 * MB, "Other a.");
+        f("other/b",            OTHER,   0.1 * MB, "Other b.");
+      }
+    }
+  ];
+
+  for (let i = 0; i < fakeReporters.length; i++) {
+    mgr.registerStrongReporterEvenIfBlocked(fakeReporters[i]);
+  }
+
+  ]]>
+  </script>
+
+  <iframe id="amFrame"  height="400" src="about:memory"></iframe>
+
+  <script type="application/javascript">
+  <![CDATA[
+  function finish()
+  {
+    mgr.unblockRegistrationAndRestoreOriginalReporters();
+    SimpleTest.finish();
+  }
+
+  // Load the given file into the frame, then copy+paste the entire frame and
+  // check that the cut text matches what we expect.
+  function test(aFilename, aFilename2, aExpected, aDumpFirst, aVerbose, aNext) {
+    let frame = document.getElementById("amFrame");
+    frame.focus();
+
+    let doc = frame.contentWindow.document;
+    let verbosity = doc.getElementById("verbose");
+    verbosity.checked = aVerbose;
+
+    function getFilePath(aFilename) {
+      let file = SpecialPowers.Services.dirsvc.get("CurWorkD", Ci.nsIFile);
+      file.append("chrome");
+      file.append("toolkit");
+      file.append("components");
+      file.append("aboutmemory");
+      file.append("tests");
+      file.append(aFilename);
+      return file.path;
+    }
+
+    let filePath = getFilePath(aFilename);
+
+    let e = document.createEvent('Event');
+    e.initEvent('change', true, true);
+
+    function check() {
+      // Initialize the clipboard contents.
+      SpecialPowers.clipboardCopyString("initial clipboard value");
+
+      let numFailures = 0, maxFailures = 30;
+
+      // Because the file load is async, we don't know when it will finish and
+      // the output will show up.  So we poll.
+      function copyPasteAndCheck() {
+        // Copy and paste frame contents, and filter out non-deterministic
+        // differences.
+        synthesizeKey("A", {accelKey: true});
+        synthesizeKey("C", {accelKey: true});
+        let actual = SpecialPowers.getClipboardData("text/plain");
+        actual = actual.replace(/\(pid \d+\)/g, "(pid NNN)");
+
+        if (actual.trim() === aExpected.trim()) {
+          SimpleTest.ok(true, "Clipboard has the expected contents");
+          aNext();
+        } else {
+          numFailures++;
+          if (numFailures === maxFailures) {
+            ok(false, "pasted text doesn't match");
+            dump("******EXPECTED******\n");
+            dump(aExpected);
+            dump("*******ACTUAL*******\n");
+            dump(actual);
+            dump("********************\n");
+            finish();
+          } else {
+            setTimeout(copyPasteAndCheck, 100);
+          }
+        }
+      }
+      copyPasteAndCheck();
+    }
+
+    if (!aFilename2) {
+      function loadAndCheck() {
+        let fileInput1 =
+          frame.contentWindow.document.getElementById("fileInput1");
+        fileInput1.value = filePath;    // this works because it's a chrome test
+
+        fileInput1.dispatchEvent(e);
+        check();
+      }
+
+      if (aDumpFirst) {
+        let dumper = Cc["@mozilla.org/memory-info-dumper;1"].
+                        getService(Ci.nsIMemoryInfoDumper);
+        dumper.dumpMemoryReportsToNamedFile(filePath, loadAndCheck, null,
+                                            /* anonymize = */ false,
+                                            /* minimize memory usage = */ false);
+      } else {
+        loadAndCheck();
+      }
+
+    } else {
+      let fileInput2 =
+        frame.contentWindow.document.getElementById("fileInput2");
+      fileInput2.value = filePath;    // this works because it's a chrome test
+
+      // Hack alert:  fileInput2's onchange handler calls fileInput2.click().
+      // But we don't want that to happen, because we want to bypass the file
+      // picker for the test.  So we set |e.skipClick|, which causes
+      // fileInput2.click() to be skipped, and dispatch the second change event
+      // directly ourselves.
+
+      e.skipClick = true;
+      fileInput2.dispatchEvent(e);
+
+      let filePath2 = getFilePath(aFilename2);
+      fileInput2.value = filePath2;    // this works because it's a chrome test
+
+      let e2 = document.createEvent('Event');
+      e2.initEvent('change', true, true);
+      fileInput2.dispatchEvent(e);
+
+      check();
+    }
+  }
+
+  // Returns a function that chains together multiple test() calls.
+  function chain(aPieces) {
+    let x = aPieces.shift();
+    if (x) {
+      return function() { test(x.filename, x.filename2, x.expected, x.dumpFirst, x.verbose, chain(aPieces)); }
+    }
+    return function() { finish(); };
+  }
+
+  let expectedGood =
+"\
+Main Process (pid NNN)\n\
+Explicit Allocations\n\
+\n\
+262,144,000 B (100.0%) -- explicit\n\
+├──209,715,200 B (80.00%) ── heap-unclassified\n\
+└───52,428,800 B (20.00%) ── a/b\n\
+\n\
+Other Measurements\n\
+\n\
+1,024 B (100.0%) -- compartments\n\
+└──1,024 B (100.0%) ── system/a\n\
+\n\
+1,024 B (100.0%) -- ghost-windows\n\
+└──1,024 B (100.0%) ── a\n\
+\n\
+314,572 B (100.0%) -- other\n\
+├──209,715 B (66.67%) ── a\n\
+└──104,857 B (33.33%) ── b\n\
+\n\
+1,024 B (100.0%) -- pss\n\
+└──1,024 B (100.0%) ── a\n\
+\n\
+1,024 B (100.0%) -- rss\n\
+└──1,024 B (100.0%) ── a\n\
+\n\
+1,024 B (100.0%) -- size\n\
+└──1,024 B (100.0%) ── a\n\
+\n\
+1,024 B (100.0%) -- swap\n\
+└──1,024 B (100.0%) ── a\n\
+\n\
+262,144,000 B ── heap-allocated\n\
+\n\
+End of Main Process (pid NNN)\n\
+Explicit-only process\n\
+\n\
+WARNING: the 'heap-allocated' memory reporter does not work for this platform and/or configuration. This means that 'heap-unclassified' is not shown and the 'explicit' tree shows less memory than it should.\n\
+Explicit Allocations\n\
+\n\
+100,000 B (100.0%) -- explicit\n\
+└──100,000 B (100.0%) ── a/b\n\
+\n\
+End of Explicit-only process\n\
+Heap-unclassified process\n\
+Explicit Allocations\n\
+\n\
+262,144,000 B (100.0%) -- explicit\n\
+├──209,715,200 B (80.00%) ── heap-unclassified\n\
+└───52,428,800 B (20.00%) ── a/b\n\
+\n\
+Other Measurements\n\
+\n\
+262,144,000 B ── heap-allocated\n\
+\n\
+End of Heap-unclassified process\n\
+Other-only process\n\
+Other Measurements\n\
+\n\
+200,000 B (100.0%) -- a\n\
+├──100,000 B (50.00%) ── b\n\
+└──100,000 B (50.00%) ── c\n\
+\n\
+500,000 B ── heap-allocated\n\
+\n\
+End of Other-only process\n\
+";
+
+  let expectedGood2 =
+"\
+Main Process (pid NNN)\n\
+Explicit Allocations\n\
+\n\
+262,144,000 B (100.0%) -- explicit\n\
+├──209,715,200 B (80.00%) ── heap-unclassified\n\
+└───52,428,800 B (20.00%) ── a/b\n\
+\n\
+Other Measurements\n\
+\n\
+314,572 B (100.0%) -- other\n\
+├──209,715 B (66.67%) ── a\n\
+└──104,857 B (33.33%) ── b\n\
+\n\
+262,144,000 B ── heap-allocated\n\
+\n\
+End of Main Process (pid NNN)\n\
+";
+
+  // This is the output for a malformed data file.
+  let expectedBad =
+"\
+Error: Invalid memory report(s): missing 'hasMozMallocUsableSize' property\
+";
+
+  // This is the output for a non-verbose diff.
+  let expectedDiffNonVerbose =
+"\
+P\n\
+\n\
+WARNING: the 'heap-allocated' memory reporter does not work for this platform and/or configuration. This means that 'heap-unclassified' is not shown and the 'explicit' tree shows less memory than it should.\n\
+Explicit Allocations\n\
+\n\
+-0.01 MB (100.0%) -- explicit\n\
+├──-0.01 MB (99.95%) ── storage/prefixset/goog-phish-shavar\n\
+└──-0.00 MB (00.05%) ++ (2 tiny)\n\
+\n\
+Other Measurements\n\
+\n\
+0.96 MB (100.0%) -- a\n\
+├──0.95 MB (99.80%) ── b\n\
+├──0.00 MB (00.10%) -- c\n\
+│  ├──-0.95 MB (-99.70%) ── e\n\
+│  ├──0.95 MB (99.60%) ── d\n\
+│  └──0.00 MB (00.20%) ++ (2 tiny)\n\
+└──0.00 MB (00.10%) ── h\n\
+\n\
+ 0.00 MB ── canvas-2d-pixel-bytes [2] [+]\n\
+-0.00 MB ── foobar [-]\n\
+\n\
+End of P\n\
+P2 (pid NNN)\n\
+\n\
+WARNING: the 'heap-allocated' memory reporter does not work for this platform and/or configuration. This means that 'heap-unclassified' is not shown and the 'explicit' tree shows less memory than it should.\n\
+Explicit Allocations\n\
+\n\
+0.00 MB (100.0%) -- explicit\n\
+└──0.00 MB (100.0%) ── window-objects/top(bar.com, id=NNN)/...\n\
+\n\
+Other Measurements\n\
+\n\
+0.00 MB (100.0%) -- p3\n\
+└──0.00 MB (100.0%) ── zone(0xNNN)/p3\n\
+\n\
+0.00 MB (100.0%) -- p4\n\
+└──0.00 MB (100.0%) ── js-zone(0xNNN)/p4\n\
+\n\
+0.00 MB (100.0%) -- p5\n\
+└──0.00 MB (100.0%) ── worker(foo.com, 0xNNN)/p5\n\
+\n\
+0.00 MB (100.0%) -- p6\n\
+└──0.00 MB (100.0%) ── z-moz-nullprincipal:{NNNNNNNN-NNNN-NNNN-NNNN-NNNNNNNNNNNN}/p6\n\
+\n\
+0.00 MB (100.0%) -- p7\n\
+└──0.00 MB (100.0%) ── js-main-runtime-compartments/system/jar:file:///.../omni.ja!/p7\n\
+\n\
+0.00 MB ── p1 (pid NNN)\n\
+0.00 MB ── p2 (blah, pid=NNN)\n\
+\n\
+End of P2 (pid NNN)\n\
+P3\n\
+Other Measurements\n\
+\n\
+-0.00 MB ── p3 [-]\n\
+\n\
+End of P3\n\
+P4\n\
+Other Measurements\n\
+\n\
+0.00 MB ── p4 [+]\n\
+\n\
+End of P4\n\
+P7\n\
+Other Measurements\n\
+\n\
+0.00 MB (100.0%) -- p7\n\
+├──0.00 MB (57.14%) ── c [+]\n\
+└──0.00 MB (42.86%) ── b [+]\n\
+\n\
+-0.00 MB ── p7 [-]\n\
+\n\
+End of P7\n\
+P8\n\
+Other Measurements\n\
+\n\
+-0.00 MB (100.0%) -- p8\n\
+└──-0.00 MB (100.0%) -- a\n\
+   ├──-0.00 MB (50.00%) -- b\n\
+   │  ├──-0.00 MB (31.82%) -- c\n\
+   │  │  ├──-0.00 MB (18.18%) ── e [-]\n\
+   │  │  └──-0.00 MB (13.64%) ── d [-]\n\
+   │  ├──-0.00 MB (22.73%) ── f [-]\n\
+   │  └───0.00 MB (-04.55%) ── (fake child) [!]\n\
+   └──-0.00 MB (50.00%) -- g\n\
+      ├──-0.00 MB (31.82%) ── i [-]\n\
+      ├──-0.00 MB (27.27%) ── h [-]\n\
+      └───0.00 MB (-09.09%) ── (fake child) [!]\n\
+\n\
+End of P8\n\
+P9\n\
+\n\
+WARNING: the 'heap-allocated' memory reporter does not work for this platform and/or configuration. This means that 'heap-unclassified' is not shown and the 'explicit' tree shows less memory than it should.\n\
+Explicit Allocations\n\
+\n\
+0.00 MB (100.0%) -- explicit\n\
+└──0.00 MB (100.0%) ── threads/stacks/DNS Resolver #N (tid=NNN) [3]\n\
+\n\
+End of P9\n\
+";
+
+  // This is the output for a verbose diff.
+  let expectedDiffVerbose =
+"\
+P\n\
+\n\
+WARNING: the 'heap-allocated' memory reporter does not work for this platform and/or configuration. This means that 'heap-unclassified' is not shown and the 'explicit' tree shows less memory than it should.\n\
+Explicit Allocations\n\
+\n\
+-10,005 B (100.0%) -- explicit\n\
+├──-10,000 B (99.95%) ── storage/prefixset/goog-phish-shavar\n\
+├───────-6 B (00.06%) ── spell-check [2]\n\
+└────────1 B (-00.01%) ── xpcom/category-manager\n\
+\n\
+Other Measurements\n\
+\n\
+1,002,000 B (100.0%) -- a\n\
+├──1,000,000 B (99.80%) ── b\n\
+├──────1,000 B (00.10%) -- c\n\
+│      ├──-999,000 B (-99.70%) ── e\n\
+│      ├──998,000 B (99.60%) ── d\n\
+│      ├──1,000 B (00.10%) ── f\n\
+│      └──1,000 B (00.10%) ── g\n\
+└──────1,000 B (00.10%) ── h\n\
+\n\
+3,000 B ── canvas-2d-pixel-bytes [2] [+]\n\
+ -100 B ── foobar [-]\n\
+\n\
+End of P\n\
+P2 (pid NNN)\n\
+\n\
+WARNING: the 'heap-allocated' memory reporter does not work for this platform and/or configuration. This means that 'heap-unclassified' is not shown and the 'explicit' tree shows less memory than it should.\n\
+Explicit Allocations\n\
+\n\
+11 B (100.0%) -- explicit\n\
+└──11 B (100.0%) ── window-objects/top(bar.com, id=NNN)/...\n\
+\n\
+Other Measurements\n\
+\n\
+11 B (100.0%) -- p3\n\
+└──11 B (100.0%) ── zone(0xNNN)/p3\n\
+\n\
+11 B (100.0%) -- p4\n\
+└──11 B (100.0%) ── js-zone(0xNNN)/p4\n\
+\n\
+11 B (100.0%) -- p5\n\
+└──11 B (100.0%) ── worker(foo.com, 0xNNN)/p5\n\
+\n\
+11 B (100.0%) -- p6\n\
+└──11 B (100.0%) ── z-moz-nullprincipal:{NNNNNNNN-NNNN-NNNN-NNNN-NNNNNNNNNNNN}/p6\n\
+\n\
+11 B (100.0%) -- p7\n\
+└──11 B (100.0%) ── js-main-runtime-compartments/system/jar:file:///.../omni.ja!/p7\n\
+\n\
+11 B ── p1 (pid NNN)\n\
+11 B ── p2 (blah, pid=NNN)\n\
+\n\
+End of P2 (pid NNN)\n\
+P3\n\
+Other Measurements\n\
+\n\
+-55 B ── p3 [-]\n\
+\n\
+End of P3\n\
+P4\n\
+Other Measurements\n\
+\n\
+66 B ── p4 [+]\n\
+\n\
+End of P4\n\
+P7\n\
+Other Measurements\n\
+\n\
+7 B (100.0%) -- p7\n\
+├──4 B (57.14%) ── c [+]\n\
+└──3 B (42.86%) ── b [+]\n\
+\n\
+-5 B ── p7 [-]\n\
+\n\
+End of P7\n\
+P8\n\
+Other Measurements\n\
+\n\
+-22 B (100.0%) -- p8\n\
+└──-22 B (100.0%) -- a\n\
+   ├──-11 B (50.00%) -- b\n\
+   │  ├───-7 B (31.82%) -- c\n\
+   │  │   ├──-4 B (18.18%) ── e [-]\n\
+   │  │   └──-3 B (13.64%) ── d [-]\n\
+   │  ├───-5 B (22.73%) ── f [-]\n\
+   │  └────1 B (-04.55%) ── (fake child) [!]\n\
+   └──-11 B (50.00%) -- g\n\
+      ├───-7 B (31.82%) ── i [-]\n\
+      ├───-6 B (27.27%) ── h [-]\n\
+      └────2 B (-09.09%) ── (fake child) [!]\n\
+\n\
+End of P8\n\
+P9\n\
+\n\
+WARNING: the 'heap-allocated' memory reporter does not work for this platform and/or configuration. This means that 'heap-unclassified' is not shown and the 'explicit' tree shows less memory than it should.\n\
+Explicit Allocations\n\
+\n\
+5,000 B (100.0%) -- explicit\n\
+└──5,000 B (100.0%) ── threads/stacks/DNS Resolver #N (tid=NNN) [3]\n\
+\n\
+End of P9\n\
+";
+
+  // This is the output for the crash reports diff.
+  let expectedDiff2 =
+"\
+Main Process (pid NNN)\n\
+Other Measurements\n\
+\n\
+1 B ── heap-allocated\n\
+\n\
+End of Main Process (pid NNN)\n\
+";
+
+  let expectedDiffFiss =
+"\
+P (pid NNN)\n\
+Explicit Allocations\n\
+\n\
+3,000,000 B (100.0%) -- explicit\n\
+├──2,999,700 B (99.99%) ── heap-unclassified\n\
+└────────300 B (00.01%) ── foobar\n\
+\n\
+Other Measurements\n\
+\n\
+3,000,000 B ── heap-allocated\n\
+\n\
+End of P (pid NNN)\n\
+web (pid NNN)\n\
+Explicit Allocations\n\
+\n\
+2,000,000 B (100.0%) -- explicit\n\
+├──1,000,000 B (50.00%) ── a/c/d\n\
+└──1,000,000 B (50.00%) ── heap-unclassified\n\
+\n\
+Other Measurements\n\
+\n\
+2,000,000 B ── heap-allocated\n\
+\n\
+End of web (pid NNN)\n\
+";
+
+  let frames = [
+    // This loads a pre-existing memory reports file that is valid.
+    { filename: "memory-reports-good.json", expected: expectedGood, dumpFirst: false, verbose: true },
+
+    // This loads a pre-existing crash dump file that is valid.
+    { filename: "crash-dump-good.json", expected: expectedGood2, dumpFirst: false, verbose: true },
+
+    // This dumps to a file and then reads it back in. (The result is the same
+    // as the previous test.)
+    { filename: "memory-reports-dumped.json.gz", expected: expectedGood2, dumpFirst: true, verbose: true },
+
+    // This loads a pre-existing file that is invalid.
+    { filename: "memory-reports-bad.json",  expected: expectedBad, dumpFirst: false, verbose: true },
+
+    // This diffs two pre-existing memory reports files.
+    { filename: "memory-reports-diff1.json", filename2: "memory-reports-diff2.json", expected: expectedDiffNonVerbose, dumpFirst: false, verbose: false },
+
+    // Ditto.
+    { filename: "memory-reports-diff1.json", filename2: "memory-reports-diff2.json", expected: expectedDiffVerbose, dumpFirst: false, verbose: true },
+
+    // This diffs two pre-existing crash report files.
+    { filename: "crash-dump-diff1.json", filename2: "crash-dump-diff2.json", expected: expectedDiff2, dumpFirst: false, verbose: true },
+
+    // This diffs a non-Fission and a Fission memory report.
+    { filename: "fiss-diff1.json", filename2: "fiss-diff2.json", expected: expectedDiffFiss, dumpFirst: false, verbose: true }
+  ];
+
+  SimpleTest.waitForFocus(chain(frames));
+
+  SimpleTest.waitForExplicitFinish();
+  ]]>
+  </script>
+</window>
diff --git a/toolkit/components/aboutmemory/tests/test_aboutmemory4.xhtml b/toolkit/components/aboutmemory/tests/test_aboutmemory4.xhtml
new file mode 100644
index 0000000000..9d9db694f2
--- /dev/null
+++ b/toolkit/components/aboutmemory/tests/test_aboutmemory4.xhtml
@@ -0,0 +1,176 @@
+<?xml version="1.0"?>
+<?xml-stylesheet type="text/css" href="chrome://global/skin"?>
+<?xml-stylesheet type="text/css" href="chrome://mochikit/content/tests/SimpleTest/test.css"?>
+<window title="about:memory"
+        xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul">
+  <script src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"/>
+  <script src="chrome://mochikit/content/tests/SimpleTest/EventUtils.js"></script>
+
+  <!-- This file tests the loading of memory reports from file when specified
+       in about:memory's URL (via the "file=" suffix). -->
+
+  <!-- test results are displayed in the html:body -->
+  <body xmlns="http://www.w3.org/1999/xhtml"></body>
+
+  <!-- test code goes here -->
+  <script type="application/javascript">
+  <![CDATA[
+  "use strict";
+
+  function makePathname(aFilename) {
+    let file = SpecialPowers.Services.dirsvc.get("CurWorkD", Ci.nsIFile);
+    file.append("chrome");
+    file.append("toolkit");
+    file.append("components");
+    file.append("aboutmemory");
+    file.append("tests");
+    file.append(aFilename);
+    return file.path;
+  }
+
+  // Load the given file into the frame, then copy+paste the entire frame and
+  // check that the cut text matches what we expect.
+  function test(aFilename, aExpected, aNext) {
+    let frame = document.createElementNS("http://www.w3.org/1999/xhtml", "iframe")
+    frame.height = 300;
+    frame.src = "about:memory?file=" + makePathname(aFilename);
+    document.documentElement.appendChild(frame);
+    frame.addEventListener("load", function onFrameLoad(e) {
+      frame.focus();
+
+      // Initialize the clipboard contents.
+      SpecialPowers.clipboardCopyString("initial clipboard value");
+
+      let numFailures = 0, maxFailures = 30;
+
+      // Because the file load is async, we don't know when it will finish and
+      // the output will show up.  So we poll.
+      function copyPasteAndCheck() {
+        // Copy and paste frame contents, and filter out non-deterministic
+        // differences.
+        synthesizeKey("A", {accelKey: true});
+        synthesizeKey("C", {accelKey: true});
+        let actual = SpecialPowers.getClipboardData("text/plain");
+        actual = actual.replace(/\(pid \d+\)/, "(pid NNN)");
+
+        if (actual.trim() === aExpected.trim()) {
+          SimpleTest.ok(true, "Clipboard has the expected contents");
+          aNext();
+        } else {
+          numFailures++;
+          if (numFailures === maxFailures) {
+            ok(false, "pasted text doesn't match");
+            dump("******EXPECTED******\n");
+            dump(aExpected);
+            dump("*******ACTUAL*******\n");
+            dump(actual);
+            dump("********************\n");
+            SimpleTest.finish();
+          } else {
+            setTimeout(copyPasteAndCheck, 100);
+          }
+        }
+      }
+      copyPasteAndCheck();
+    }, {once: true});
+  }
+
+  // Returns a function that chains together multiple test() calls.
+  function chain(aFrameIds) {
+    let x = aFrameIds.shift();
+    if (x) {
+      return function() { test(x.filename, x.expected, chain(aFrameIds)); }
+    }
+    return function() { SimpleTest.finish(); };
+  }
+
+  // This is pretty simple output, but that's ok;  this file is about testing
+  // the loading of data from file.  If we got this far, we're doing fine.
+  let expectedGood =
+"\
+Main Process (pid NNN)\n\
+Explicit Allocations\n\
+\n\
+250.00 MB (100.0%) -- explicit\n\
+├──200.00 MB (80.00%) ── heap-unclassified\n\
+└───50.00 MB (20.00%) ── a/b\n\
+\n\
+Other Measurements\n\
+\n\
+0.00 MB (100.0%) -- compartments\n\
+└──0.00 MB (100.0%) ── system/a\n\
+\n\
+0.00 MB (100.0%) -- ghost-windows\n\
+└──0.00 MB (100.0%) ── a\n\
+\n\
+0.30 MB (100.0%) -- other\n\
+├──0.20 MB (66.67%) ── a\n\
+└──0.10 MB (33.33%) ── b\n\
+\n\
+0.00 MB (100.0%) -- pss\n\
+└──0.00 MB (100.0%) ── a\n\
+\n\
+0.00 MB (100.0%) -- rss\n\
+└──0.00 MB (100.0%) ── a\n\
+\n\
+0.00 MB (100.0%) -- size\n\
+└──0.00 MB (100.0%) ── a\n\
+\n\
+0.00 MB (100.0%) -- swap\n\
+└──0.00 MB (100.0%) ── a\n\
+\n\
+250.00 MB ── heap-allocated\n\
+\n\
+End of Main Process (pid NNN)\n\
+Explicit-only process\n\
+\n\
+WARNING: the 'heap-allocated' memory reporter does not work for this platform and/or configuration. This means that 'heap-unclassified' is not shown and the 'explicit' tree shows less memory than it should.\n\
+Explicit Allocations\n\
+\n\
+0.10 MB (100.0%) -- explicit\n\
+└──0.10 MB (100.0%) ── a/b\n\
+\n\
+End of Explicit-only process\n\
+Heap-unclassified process\n\
+Explicit Allocations\n\
+\n\
+250.00 MB (100.0%) -- explicit\n\
+├──200.00 MB (80.00%) ── heap-unclassified\n\
+└───50.00 MB (20.00%) ── a/b\n\
+\n\
+Other Measurements\n\
+\n\
+250.00 MB ── heap-allocated\n\
+\n\
+End of Heap-unclassified process\n\
+Other-only process\n\
+Other Measurements\n\
+\n\
+0.19 MB (100.0%) -- a\n\
+├──0.10 MB (50.00%) ── b\n\
+└──0.10 MB (50.00%) ── c\n\
+\n\
+0.48 MB ── heap-allocated\n\
+\n\
+End of Other-only process\n\
+";
+
+  // This is the output for a malformed data file.
+  let expectedBad =
+"\
+Error: Invalid memory report(s): missing 'hasMozMallocUsableSize' property";
+
+  let frames = [
+    // This loads a pre-existing file that is valid.
+    { filename: "memory-reports-good.json", expected: expectedGood },
+
+    // This loads a pre-existing file that is valid.
+    { filename: "memory-reports-bad.json", expected: expectedBad }
+  ];
+
+  SimpleTest.waitForFocus(chain(frames));
+
+  SimpleTest.waitForExplicitFinish();
+  ]]>
+  </script>
+</window>
diff --git a/toolkit/components/aboutmemory/tests/test_aboutmemory5.xhtml b/toolkit/components/aboutmemory/tests/test_aboutmemory5.xhtml
new file mode 100644
index 0000000000..7b63179767
--- /dev/null
+++ b/toolkit/components/aboutmemory/tests/test_aboutmemory5.xhtml
@@ -0,0 +1,169 @@
+<?xml version="1.0"?>
+<?xml-stylesheet type="text/css" href="chrome://global/skin"?>
+<?xml-stylesheet type="text/css" href="chrome://mochikit/content/tests/SimpleTest/test.css"?>
+<window title="about:memory"
+        xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul">
+  <script src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"/>
+  <script src="chrome://mochikit/content/tests/SimpleTest/EventUtils.js"></script>
+
+  <!-- This file tests the saving and loading of memory reports to/from file in
+       about:memory in the presence of child processes.  It is also notable
+       for being an about:memory test that uses the real reporters, rather
+       than fake deterministic ones, and so tends to show up problems in the
+       real reporters (like bogus negative values). -->
+
+  <!-- test results are displayed in the html:body -->
+  <body xmlns="http://www.w3.org/1999/xhtml"></body>
+
+  <iframe id="amFrame"  height="400" src="about:memory"></iframe>
+
+  <script type="application/javascript">
+  <![CDATA[
+  "use strict";
+
+  let mgr = Cc["@mozilla.org/memory-reporter-manager;1"].
+            getService(Ci.nsIMemoryReporterManager);
+
+  let numRemotes = 3;
+  let numReady = 0;
+
+  // Create some remote processes, and set up message-passing so that
+  // we know when each child is fully initialized.
+  let remotes = [];
+
+  let prefs = [
+    ["dom.ipc.processCount", 3],            // Allow up to 3 child processes
+    ["memory.report_concurrency", 2]        // Cover more child handling cases
+  ];
+
+  SpecialPowers.pushPrefEnv({"set": prefs}).then(function() {
+    for (let i = 0; i < numRemotes; i++) {
+      let w = remotes[i] = window.browsingContext.topChromeWindow.open("remote.xhtml", "", "chrome");
+
+      w.addEventListener("load", function loadHandler() {
+        let remoteBrowser = w.document.getElementById("remote");
+        let mm = remoteBrowser.messageManager;
+        mm.addMessageListener("test:ready", function readyHandler() {
+          mm.removeMessageListener("test:ready", readyHandler);
+          numReady++;
+          if (numReady == numRemotes) {
+            // All the remote processes are ready.
+            SimpleTest.waitForFocus(onFocus);
+          }
+        });
+        mm.loadFrameScript("data:," + encodeURI("sendAsyncMessage('test:ready');"), true);
+      });
+    }
+  });
+
+  // Load the given file into the frame, then copy+paste the entire frame and
+  // check that the cut text matches what we expect.
+  function onFocus() {
+    let frame = document.getElementById("amFrame");
+    frame.focus();
+
+    function getFilePath(aFilename) {
+      let file = SpecialPowers.Services.dirsvc.get("CurWorkD", Ci.nsIFile);
+      file.append("chrome");
+      file.append("toolkit");
+      file.append("components");
+      file.append("aboutmemory");
+      file.append("tests");
+      file.append(aFilename);
+      return file.path;
+    }
+
+    let filePath = getFilePath("memory-reports-dumped.json.gz");
+
+    let e = document.createEvent('Event');
+    e.initEvent('change', true, true);
+
+    let dumper = Cc["@mozilla.org/memory-info-dumper;1"].
+                    getService(Ci.nsIMemoryInfoDumper);
+    dumper.dumpMemoryReportsToNamedFile(filePath, loadAndCheck, null,
+                                        /* anonymize = */ false,
+                                        /* minimize memory usage = */ false);
+
+    function loadAndCheck() {
+      // Load the file.
+      let fileInput1 =
+        frame.contentWindow.document.getElementById("fileInput1");
+      fileInput1.value = filePath;    // this works because it's a chrome test
+      fileInput1.dispatchEvent(e);
+
+      // Initialize the clipboard contents.
+      SpecialPowers.clipboardCopyString("initial clipboard value");
+
+      let numFailures = 0, maxFailures = 30;
+
+      copyPasteAndCheck();
+
+      // Because the file load is async, we don't know when it will finish and
+      // the output will show up.  So we poll.
+      function copyPasteAndCheck() {
+        // Copy and paste frame contents, and filter out non-deterministic
+        // differences.
+        synthesizeKey("A", {accelKey: true});
+        synthesizeKey("C", {accelKey: true});
+        let actual = SpecialPowers.getClipboardData("text/plain");
+
+        // If we have more than 1000 chars, we've probably successfully
+        // copy+pasted.
+        if (actual.length > 1000) {
+
+          let good = true;
+
+          if (actual.match("End of System")) {
+            let m1 = actual.match("anonymous") &&
+                     actual.match("shared-libraries");
+            ok(m1, "system-wide reporter")
+            good = good && !!m1;
+          }
+
+          // Note: Match "vsize" but not "vsize-max-contiguous".
+          let vsizes = actual.match(/vsize[^-]/g);
+          let endOfBrowsers = actual.match(/End of Browser/g);
+          if (endOfBrowsers == null) {
+            endOfBrowsers = actual.match(/End of [wW]eb /g);
+          }
+
+          let socketProcessRunning = 0;
+          if (SpecialPowers.Services.io.socketProcessLaunched) {
+            socketProcessRunning = 1;
+          }
+
+          let m2 = (vsizes.length == (4 + socketProcessRunning + ChromeUtils.aliveUtilityProcesses) &&
+                    endOfBrowsers.length == 3);
+          ok(m2, "three content processes present in loaded data");
+          good = good && !!m2;
+
+          if (!good) {
+            dump("*******ACTUAL*******\n");
+            dump(actual);
+            dump("********************\n");
+          }
+
+          // Close the remote processes.
+          for (let i = 0; i < numRemotes; i++) {
+            remotes[i].close();
+          }
+
+          SimpleTest.finish();
+
+        } else {
+          numFailures++;
+          if (numFailures === maxFailures) {
+            ok(false, "not enough chars in pasted output");
+            SimpleTest.finish();
+          } else {
+            setTimeout(copyPasteAndCheck, 100);
+          }
+        }
+      }
+    }
+  }
+
+  SimpleTest.waitForExplicitFinish();
+  ]]>
+  </script>
+</window>
diff --git a/toolkit/components/aboutmemory/tests/test_aboutmemory6.xhtml b/toolkit/components/aboutmemory/tests/test_aboutmemory6.xhtml
new file mode 100644
index 0000000000..a3a76532e7
--- /dev/null
+++ b/toolkit/components/aboutmemory/tests/test_aboutmemory6.xhtml
@@ -0,0 +1,85 @@
+<?xml version="1.0"?>
+<?xml-stylesheet type="text/css" href="chrome://global/skin"?>
+<?xml-stylesheet type="text/css" href="chrome://mochikit/content/tests/SimpleTest/test.css"?>
+<window title="about:memory"
+        xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul">
+  <script src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"/>
+  <script src="chrome://mochikit/content/tests/SimpleTest/EventUtils.js"></script>
+
+  <!-- This file tests the saving of GC and CC logs in both concise and
+       verbose formats. -->
+
+  <!-- test results are displayed in the html:body -->
+  <body xmlns="http://www.w3.org/1999/xhtml"></body>
+
+  <iframe id="amFrame"  height="400" src="about:memory"></iframe>
+
+  <script type="application/javascript">
+  <![CDATA[
+  "use strict";
+
+  function onFocus() {
+    let frame = document.getElementById("amFrame");
+    frame.focus();
+
+    // Checks that a file exists on the local file system and removes it if it
+    // is present.
+    function checkForFileAndRemove(aFilename) {
+      let localFile = Cc["@mozilla.org/file/local;1"]
+                        .createInstance(Ci.nsIFile);
+      localFile.initWithPath(aFilename);
+
+      let exists = localFile.exists();
+      if (exists) {
+        localFile.remove(/* recursive = */ false);
+      }
+
+      return exists;
+    }
+
+    // Given a save log button, triggers the action and checks if both CC & GC
+    // logs were written to disk.
+    function saveLogs(aLogButton, aCCLogType)
+    {
+      // trigger the log saving
+      aLogButton.click();
+
+      // mainDiv
+      // |-> section
+      //        | -> div gc log path
+      //        | -> div cc log path
+      let mainDiv = frame.contentWindow.document.getElementById("mainDiv");
+      let logNodes = mainDiv.childNodes[0];
+
+      // we expect 2 logs listed
+      let numOfLogs = logNodes.childNodes.length;
+      ok(numOfLogs == 2, "two log entries generated")
+
+      // grab the path portion of the text
+      let gcLogPath = logNodes.childNodes[0].textContent
+                        .replace("Saved GC log to ", "");
+      let ccLogPath = logNodes.childNodes[1].textContent
+                        .replace("Saved " + aCCLogType + " CC log to ", "");
+
+      // check that the files actually exist
+      ok(checkForFileAndRemove(gcLogPath), "GC log file exists");
+      ok(checkForFileAndRemove(ccLogPath), "CC log file exists");
+    }
+
+    // get the log buttons to test
+    let saveConcise = frame.contentWindow.document
+                        .getElementById("saveLogsConcise");
+    let saveVerbose = frame.contentWindow.document
+                        .getElementById("saveLogsVerbose");
+
+    saveLogs(saveConcise, "concise");
+    saveLogs(saveVerbose, "verbose");
+
+    SimpleTest.finish();
+  }
+
+  SimpleTest.waitForFocus(onFocus);
+  SimpleTest.waitForExplicitFinish();
+  ]]>
+  </script>
+</window>
diff --git a/toolkit/components/aboutmemory/tests/test_aboutmemory7.xhtml b/toolkit/components/aboutmemory/tests/test_aboutmemory7.xhtml
new file mode 100644
index 0000000000..28872cd516
--- /dev/null
+++ b/toolkit/components/aboutmemory/tests/test_aboutmemory7.xhtml
@@ -0,0 +1,215 @@
+<?xml version="1.0"?>
+<?xml-stylesheet type="text/css" href="chrome://global/skin"?>
+<?xml-stylesheet type="text/css" href="chrome://mochikit/content/tests/SimpleTest/test.css"?>
+<window title="about:memory"
+        xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul">
+  <script src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"/>
+  <script src="chrome://mochikit/content/tests/SimpleTest/EventUtils.js"></script>
+
+  <!-- This file tests filtering in about:memory. -->
+
+  <!-- test results are displayed in the html:body -->
+  <body xmlns="http://www.w3.org/1999/xhtml"></body>
+
+  <!-- test code goes here -->
+  <script type="application/javascript">
+  <![CDATA[
+  "use strict";
+
+  let mgr = Cc["@mozilla.org/memory-reporter-manager;1"].
+            getService(Ci.nsIMemoryReporterManager);
+
+  // Hide all the real reporters;  we'll restore them at the end.
+  mgr.blockRegistrationAndHideExistingReporters();
+
+  // Setup various fake-but-deterministic reporters.
+  const KB = 1024;
+  const MB = KB * KB;
+  const HEAP  = Ci.nsIMemoryReporter.KIND_HEAP;
+  const OTHER = Ci.nsIMemoryReporter.KIND_OTHER;
+  const BYTES = Ci.nsIMemoryReporter.UNITS_BYTES;
+
+  let fakeReporters = [
+    { collectReports(aCbObj, aClosure, aAnonymize) {
+        function f(aP, aK, aA) {
+          aCbObj.callback("Main Process", aP, aK, BYTES, aA, "Desc.", aClosure);
+        }
+        f("heap-allocated",     OTHER,   250 * MB);
+        f("explicit/a/b",       HEAP,     50 * MB);
+        f("explicit/a/c/d",     HEAP,     25 * MB);
+        f("explicit/a/c/e",     HEAP,     15 * MB);
+        f("explicit/a/f",       HEAP,     30 * MB);
+        f("explicit/g",         HEAP,    100 * MB);
+        f("explicit/h/i",       HEAP,     10 * MB);
+        f("explicit/h/i2",      HEAP,      9 * MB);
+        f("explicit/j/k",       HEAP,    0.5 * MB);
+        f("explicit/j/k2",      HEAP,    0.3 * MB);
+        f("explicit/a/l/m",     HEAP,    0.1 * MB);
+        f("explicit/a/l/n",     HEAP,    0.1 * MB);
+      }
+    }
+  ];
+
+  for (let i = 0; i < fakeReporters.length; i++) {
+    mgr.registerStrongReporterEvenIfBlocked(fakeReporters[i]);
+  }
+
+  ]]>
+  </script>
+
+  <iframe id="amFrame"  height="500" src="about:memory"></iframe>
+
+  <script type="application/javascript">
+  <![CDATA[
+  function finish()
+  {
+    mgr.unblockRegistrationAndRestoreOriginalReporters();
+    SimpleTest.finish();
+  }
+
+  // Click on the identified element, then cut+paste the entire page and
+  // check that the cut text matches what we expect.
+  function testClick(aId, aExpected, aNext) {
+    let win = document.getElementById("amFrame").contentWindow;
+
+    win.document.getElementById(aId).click();
+
+    testClipboard(aExpected, aNext, 0);
+  }
+
+  // Apply the specified filter, then cut+paste the entire page and
+  // check that the cut text matches what we expect.
+  function testFilter(aFilterString, aRegEx, aExpected, aNext) {
+    let win = document.getElementById("amFrame").contentWindow;
+
+    let filterInput = win.document.querySelector(".filterInput");
+    let filterRegExCheckbox =
+      win.document.querySelector(".filterInput + * input[type=checkbox]");
+
+    filterInput.value = aFilterString;
+    filterRegExCheckbox.checked = aRegEx;
+
+    // Dispatch a synthetic input event, since assigning to .value above
+    // doesn't trigger this.
+    filterInput.dispatchEvent(new win.Event("input"));
+
+    // about:memory delays 300 ms before applying the filter, so we wait a
+    // a bit longer than that before checking the clipboard.
+    testClipboard(aExpected, aNext, /* delay */ 600);
+  }
+
+  function testClipboard(aExpected, aNext, aDelay) {
+    setTimeout(function() {
+      let mostRecentActual;
+      document.getElementById("amFrame").focus();
+      SimpleTest.waitForClipboard(
+        function(aActual) {
+          mostRecentActual = aActual;
+          let rslt = aActual.trim() === aExpected.trim();
+          if (!rslt) {
+            // Try copying again.
+            synthesizeKey("A", {accelKey: true});
+            synthesizeKey("C", {accelKey: true});
+          }
+
+          return rslt;
+        },
+        function() {
+          synthesizeKey("A", {accelKey: true});
+          synthesizeKey("C", {accelKey: true});
+        },
+        aNext,
+        function() {
+          ok(false, "pasted text doesn't match");
+          dump("******EXPECTED******\n");
+          dump(aExpected);
+          dump("*******ACTUAL*******\n");
+          dump(mostRecentActual);
+          dump("********************\n");
+          finish();
+        }
+      );
+    }, aDelay);
+  }
+
+  // Returns a function that chains together one test() call per id.
+  function chain(aIds) {
+    let x = aIds.shift();
+    if (x) {
+      if (x.click) {
+        return function() { testClick(x.click, x.expected, chain(aIds)); }
+      }
+      return function() { testFilter(x.filter, x.regex, x.expected, chain(aIds)); }
+    }
+    return function() { finish(); };
+  }
+
+  let startExpected =
+"\
+Main Process\n\
+Explicit Allocations\n\
+\n\
+250.00 MB (100.0%) -- explicit\n\
+├──120.20 MB (48.08%) -- a\n\
+│  ├───50.00 MB (20.00%) ── b\n\
+│  ├───40.00 MB (16.00%) -- c\n\
+│  │   ├──25.00 MB (10.00%) ── d\n\
+│  │   └──15.00 MB (06.00%) ── e\n\
+│  ├───30.00 MB (12.00%) ── f\n\
+│  └────0.20 MB (00.08%) ++ l\n\
+├──100.00 MB (40.00%) ── g\n\
+├───19.00 MB (07.60%) -- h\n\
+│   ├──10.00 MB (04.00%) ── i\n\
+│   └───9.00 MB (03.60%) ── i2\n\
+├───10.00 MB (04.00%) ── heap-unclassified\n\
+└────0.80 MB (00.32%) ++ j\n\
+\n\
+Other Measurements\n\
+\n\
+250.00 MB ── heap-allocated\n\
+\n\
+End of Main Process\n\
+";
+
+  let acFilterExpected =
+"\
+Main Process\n\
+Explicit Allocations\n\
+\n\
+40.00 MB (100.0%) -- explicit\n\
+└──40.00 MB (100.0%) -- a/c\n\
+   ├──25.00 MB (62.50%) ── d\n\
+   └──15.00 MB (37.50%) ── e\n\
+\n\
+End of Main Process\n\
+";
+
+  let hjFilterExpected =
+"\
+Main Process\n\
+Explicit Allocations\n\
+\n\
+19.80 MB (100.0%) -- explicit\n\
+├──19.00 MB (95.96%) -- h\n\
+│  ├──10.00 MB (50.51%) ── i\n\
+│  └───9.00 MB (45.45%) ── i2\n\
+└───0.80 MB (04.04%) -- j\n\
+    ├──0.50 MB (02.53%) ── k\n\
+    └──0.30 MB (01.52%) ── k2\n\
+\n\
+End of Main Process\n\
+";
+
+  let filtersToApplyOrIdsToClick = [
+    { click: "measureButton",               expected: startExpected },
+    { filter: "a/c",          regex: false, expected: acFilterExpected },
+    { filter: "/[hj]",        regex: false, expected: "No results found." },
+    { filter: "/[hj]",        regex: true,  expected: hjFilterExpected },
+  ];
+
+  SimpleTest.waitForFocus(chain(filtersToApplyOrIdsToClick));
+
+  SimpleTest.waitForExplicitFinish();
+  ]]>
+  </script>
+</window>
diff --git a/toolkit/components/aboutmemory/tests/test_dumpGCAndCCLogsToFile.xhtml b/toolkit/components/aboutmemory/tests/test_dumpGCAndCCLogsToFile.xhtml
new file mode 100644
index 0000000000..9f3cdfe774
--- /dev/null
+++ b/toolkit/components/aboutmemory/tests/test_dumpGCAndCCLogsToFile.xhtml
@@ -0,0 +1,90 @@
+<?xml version="1.0"?>
+<?xml-stylesheet href="chrome://global/skin" type="text/css"?>
+<?xml-stylesheet href="chrome://mochikit/content/tests/SimpleTest/test.css"
+                 type="text/css"?>
+<window title="GC/CC logging with child processes"
+  xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul">
+  <script src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"/>
+
+  <!-- test results are displayed in the html:body -->
+  <body xmlns="http://www.w3.org/1999/xhtml">
+  </body>
+
+  <!-- test code goes here -->
+  <script type="application/javascript"><![CDATA[
+
+  SimpleTest.waitForExplicitFinish();
+
+  let numRemotes = 3;
+  let numReady = 0;
+
+  // Create some remote processes, and set up message-passing so that
+  // we know when each child is fully initialized.
+  let remotes = [];
+  SpecialPowers.pushPrefEnv({"set": [["dom.ipc.processCount", numRemotes]]}).then(function() {
+    for (let i = 0; i < numRemotes; i++) {
+      let w = remotes[i] = window.browsingContext.topChromeWindow.open("remote.xhtml", "", "chrome");
+
+      w.addEventListener("load", function loadHandler() {
+        let remoteBrowser = w.document.getElementById("remote");
+        let mm = remoteBrowser.messageManager;
+        mm.addMessageListener("test:ready", function readyHandler() {
+          mm.removeMessageListener("test:ready", readyHandler);
+          numReady++;
+          if (numReady == numRemotes) {
+            // All the remote processes are ready.  Run test.
+            runTest();
+          }
+        });
+        mm.loadFrameScript("data:," + encodeURI("sendAsyncMessage('test:ready');"), true);
+      }, {once: true});
+    }
+  });
+
+  let dumper = Cc["@mozilla.org/memory-info-dumper;1"].
+               getService(Ci.nsIMemoryInfoDumper);
+
+  function runTest() {
+    let numParents = 0;
+    let numChildren = 0;
+    dumper.dumpGCAndCCLogsToFile(
+      /* identifier: */ "test." + Date.now(),
+      /* allTraces: */ false,
+      /* childProcesses: */ true,
+      {
+        onDump(gcLog, ccLog, isParent) {
+          if (isParent) {
+            numParents++;
+          } else {
+            numChildren++;
+          }
+          checkAndRemoveLog(gcLog);
+          checkAndRemoveLog(ccLog);
+        },
+        onFinish() {
+          is(numParents, 1, "GC/CC logs for the parent process");
+          is(numChildren, numRemotes, "GC/CC logs for each child process");
+          cleanUpAndFinish();
+        },
+      }
+    );
+  }
+
+  function cleanUpAndFinish() {
+      // Close the remote processes.
+      for (let i = 0; i < numRemotes; i++) {
+          remotes[i].close();
+      }
+      SimpleTest.finish();
+  }
+
+  function checkAndRemoveLog(logFile) {
+      let name = logFile.path;
+      ok(logFile.exists(), "log file "+name+" exists");
+      ok(logFile.isFile(), "log file "+name+" is a regular file");
+      ok(logFile.fileSize > 0, "log file "+name+" is not empty");
+      logFile.remove(/* recursive: */ false);
+  }
+
+  ]]></script>
+</window>
diff --git a/toolkit/components/aboutmemory/tests/test_memoryReporters.xhtml b/toolkit/components/aboutmemory/tests/test_memoryReporters.xhtml
new file mode 100644
index 0000000000..c97981258e
--- /dev/null
+++ b/toolkit/components/aboutmemory/tests/test_memoryReporters.xhtml
@@ -0,0 +1,433 @@
+<?xml version="1.0"?>
+<?xml-stylesheet type="text/css" href="chrome://global/skin"?>
+<?xml-stylesheet type="text/css" href="chrome://mochikit/content/tests/SimpleTest/test.css"?>
+<window title="Memory reporters"
+        xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul">
+  <script src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"/>
+
+  <!-- This file tests (in a rough fashion) whether the memory reporters are
+       producing sensible results.  test_aboutmemory.xhtml tests the
+       presentation of memory reports in about:memory. -->
+
+  <!-- test results are displayed in the html:body -->
+  <body xmlns="http://www.w3.org/1999/xhtml">
+  <!-- In bug 773533, <marquee> elements crashed the JS memory reporter -->
+  <marquee>Marquee</marquee>
+  </body>
+
+  <!-- some URIs that should be anonymized in anonymous mode -->
+  <iframe id="amFrame"  height="200" src="http://example.org:80"></iframe>
+  <iframe id="amFrame"  height="200" src="https://example.com:443"></iframe>
+
+  <!-- test code goes here -->
+  <script type="application/javascript">
+  <![CDATA[
+
+  "use strict";
+
+  const NONHEAP = Ci.nsIMemoryReporter.KIND_NONHEAP;
+  const HEAP    = Ci.nsIMemoryReporter.KIND_HEAP;
+  const OTHER   = Ci.nsIMemoryReporter.KIND_OTHER;
+
+  const BYTES = Ci.nsIMemoryReporter.UNITS_BYTES;
+  const COUNT = Ci.nsIMemoryReporter.UNITS_COUNT;
+  const COUNT_CUMULATIVE = Ci.nsIMemoryReporter.UNITS_COUNT_CUMULATIVE;
+  const PERCENTAGE = Ci.nsIMemoryReporter.UNITS_PERCENTAGE;
+
+  // Use backslashes instead of forward slashes due to memory reporting's hacky
+  // handling of URLs.
+  const XUL_NS =
+    "http:\\\\www.mozilla.org\\keymaster\\gatekeeper\\there.is.only.xul";
+
+  SimpleTest.waitForExplicitFinish();
+
+  let vsizeAmounts = [];
+  let residentAmounts = [];
+  let heapAllocatedAmounts = [];
+  let storageSqliteAmounts = [];
+
+  let jsGcHeapUsedGcThingsTotal = 0;
+  let jsGcHeapUsedGcThings = {};
+
+  let present = {}
+
+  // Generate a long, random string.  We'll check that this string is
+  // reported in at least one of the memory reporters.
+  let bigString = "";
+  while (bigString.length < 10000) {
+    bigString += Math.random();
+  }
+  let bigStringPrefix = bigString.substring(0, 100);
+
+  // Generate many copies of two distinctive short strings, "!)(*&" and
+  // "@)(*&". We'll check that these strings are reported in at least one of
+  // the memory reporters. We will create these strings in the tenured heap to
+  // avoid nursery string deduplication.
+  let shortStrings = [];
+  let newString = Cu.getJSTestingFunctions().newString;
+  for (let i = 0; i < 10000; i++) {
+    let str = (Math.random() > 0.5 ? "!" : "@") + ")(*&";
+    shortStrings.push(newString(str, {tenured: true}));
+  }
+
+  // Strings in the nursery are not reported, so make sure the above test
+  // strings are tenured (not all are created tenured).
+  Cu.forceGC();
+
+  let mySandbox = Cu.Sandbox(document.nodePrincipal,
+                    { sandboxName: "this-is-a-sandbox-name" });
+
+  function handleReportNormal(aProcess, aPath, aKind, aUnits, aAmount,
+                              aDescription)
+  {
+    if (aProcess.startsWith(`Utility `)) {
+      // The Utility process that runs the ORB JavaScript validator starts on first
+      // idle in the parent process. This makes it notoriously hard to know _if_ it
+      // actually has started. So we bail. See Bug 1813985.
+      return;
+    }
+    // Record the values of some notable reporters.
+    if (aPath === "vsize") {
+      vsizeAmounts.push(aAmount);
+    } else if (aPath === "resident") {
+      residentAmounts.push(aAmount);
+    } else if (aPath.search(/^js-main-runtime-gc-heap-committed\/used\/gc-things\//) >= 0) {
+      jsGcHeapUsedGcThingsTotal += aAmount;
+      jsGcHeapUsedGcThings[aPath] = (jsGcHeapUsedGcThings[aPath] | 0) + 1;
+    } else if (aPath === "heap-allocated") {
+      heapAllocatedAmounts.push(aAmount);
+    } else if (aPath === "storage-sqlite") {
+      storageSqliteAmounts.push(aAmount);
+
+    // Check the presence of some other notable reporters.
+    } else if (aPath.search(/^explicit\/js-non-window\/.*realm\(/) >= 0) {
+      present.jsNonWindowRealms = true;
+    } else if (aPath.search(/^explicit\/window-objects\/top\(.*\/js-realm\(/) >= 0) {
+      present.windowObjectsJsRealms = true;
+    } else if (aPath.search(/^explicit\/storage\/sqlite\/places.sqlite/) >= 0) {
+      present.places = true;
+    } else if (aPath.search(/^explicit\/images/) >= 0) {
+      present.images = true;
+    } else if (aPath.search(/^explicit\/atoms\/dynamic-objects-and-chars$/) >= 0) {
+      present.dynamicObjectsAndChars = true;
+    } else if (/\[System Principal\].*this-is-a-sandbox-name/.test(aPath)) {
+      // A system compartment with a location (such as a sandbox) should
+      // show that location.
+      present.sandboxLocation = true;
+    } else if (aPath.includes(bigStringPrefix)) {
+      present.bigString = true;
+    } else if (aPath.includes("!)(*&")) {
+      present.smallString1 = true;
+    } else if (aPath.includes("@)(*&")) {
+      present.smallString2 = true;
+    }
+
+    // Shouldn't get any anonymized paths.
+    if (aPath.includes('<anonymized')) {
+        present.anonymizedWhenUnnecessary = aPath;
+    }
+  }
+
+  function handleReportAnonymized(aProcess, aPath, aKind, aUnits, aAmount,
+                                  aDescription)
+  {
+    // Path might include an xmlns using http, which is safe to ignore.
+    let reducedPath = aPath.replace(XUL_NS, "");
+
+    // Shouldn't get http: or https: in any paths.
+    if (reducedPath.includes('http:')) {
+        present.httpWhenAnonymized = aPath;
+    }
+
+    // file: URLs should have their path anonymized.
+    if (reducedPath.search('file:..[^<]') !== -1) {
+        present.unanonymizedFilePathWhenAnonymized = aPath;
+    }
+  }
+
+  let mgr = Cc["@mozilla.org/memory-reporter-manager;1"].
+            getService(Ci.nsIMemoryReporterManager);
+
+  let amounts = [
+    "vsize",
+    "vsizeMaxContiguous",
+    "resident",
+    "residentFast",
+    "residentPeak",
+    "residentUnique",
+    "heapAllocated",
+    "heapOverheadFraction",
+    "JSMainRuntimeGCHeap",
+    "JSMainRuntimeTemporaryPeak",
+    "JSMainRuntimeRealmsSystem",
+    "JSMainRuntimeRealmsUser",
+    "imagesContentUsedUncompressed",
+    "storageSQLite",
+    "lowMemoryEventsPhysical",
+    "ghostWindows",
+    "pageFaultsHard",
+  ];
+  for (let i = 0; i < amounts.length; i++) {
+    try {
+      // If mgr[amounts[i]] throws an exception, just move on -- some amounts
+      // aren't available on all platforms.  But if the attribute simply
+      // isn't present, that indicates the distinguished amounts have changed
+      // and this file hasn't been updated appropriately.
+      let dummy = mgr[amounts[i]];
+      ok(dummy !== undefined,
+         "accessed an unknown distinguished amount: " + amounts[i]);
+    } catch (ex) {
+    }
+  }
+
+  // Run sizeOfTab() to make sure it doesn't crash.  We can't check the result
+  // values because they're non-deterministic.
+  let jsObjectsSize = {};
+  let jsStringsSize = {};
+  let jsOtherSize = {};
+  let domSize = {};
+  let styleSize = {};
+  let otherSize = {};
+  let totalSize = {};
+  let jsMilliseconds = {};
+  let nonJSMilliseconds = {};
+  mgr.sizeOfTab(window, jsObjectsSize, jsStringsSize, jsOtherSize,
+                domSize, styleSize, otherSize, totalSize,
+                jsMilliseconds, nonJSMilliseconds);
+
+  let asyncSteps = [
+    getReportsNormal,
+    getReportsAnonymized,
+    checkResults,
+    test_register_strong,
+    test_register_strong, // Make sure re-registering works
+    test_register_weak,
+    SimpleTest.finish
+  ];
+
+  function runNext() {
+    setTimeout(asyncSteps.shift(), 0);
+  }
+
+  function getReportsNormal()
+  {
+    mgr.getReports(handleReportNormal, null,
+                   runNext, null,
+                   /* anonymize = */ false);
+  }
+
+  function getReportsAnonymized()
+  {
+    mgr.getReports(handleReportAnonymized, null,
+                   runNext, null,
+                   /* anonymize = */ true);
+  }
+
+  function checkSizeReasonable(aName, aAmount)
+  {
+    // Check the size is reasonable -- i.e. not ridiculously large or small.
+    ok(100 * 1000 <= aAmount && aAmount <= 10 * 1000 * 1000 * 1000,
+       aName + "'s size is reasonable");
+  }
+
+  function checkSpecialReport(aName, aAmounts, aCanBeUnreasonable)
+  {
+    let socketProcessRunning = 0;
+    if (SpecialPowers.Services.io.socketProcessLaunched) {
+      socketProcessRunning = 1;
+    }
+    is(aAmounts.length, 1 + socketProcessRunning,
+       aName + " has " + aAmounts.length + " report");
+    let n = aAmounts[0];
+    if (!aCanBeUnreasonable) {
+      checkSizeReasonable(aName, n);
+    }
+  }
+
+  function checkResults()
+  {
+    try {
+      // Nb: mgr.heapAllocated will throw NS_ERROR_NOT_AVAILABLE if this is a
+      // --disable-jemalloc build.  Allow for skipping this test on that
+      // exception, but *only* that exception.
+      // eslint-disable-next-line no-unused-vars
+      let dummy = mgr.heapAllocated;
+      checkSpecialReport("heap-allocated", heapAllocatedAmounts);
+    } catch (ex) {
+      is(ex.result, Cr.NS_ERROR_NOT_AVAILABLE, "mgr.heapAllocated exception");
+    }
+    // vsize may be unreasonable if ASAN is enabled
+    checkSpecialReport("vsize",          vsizeAmounts, /*canBeUnreasonable*/true);
+    checkSpecialReport("resident",       residentAmounts);
+
+    for (var reporter in jsGcHeapUsedGcThings) {
+      ok(jsGcHeapUsedGcThings[reporter] == 1);
+    }
+    checkSizeReasonable("js-main-runtime-gc-heap-committed/used/gc-things",
+                        jsGcHeapUsedGcThingsTotal);
+
+    ok(present.jsNonWindowRealms,           "js-non-window realms are present");
+    ok(present.windowObjectsJsRealms,       "window-objects/.../js realms are present");
+    ok(present.places,                      "places is present");
+    ok(present.images,                      "images is present");
+    ok(present.dynamicObjectsAndChars,      "dynamic-objects-and-chars is present");
+    ok(present.sandboxLocation,             "sandbox locations are present");
+    ok(present.bigString,                   "large string is present");
+    ok(present.smallString1,                "small string 1 is present");
+    ok(present.smallString2,                "small string 2 is present");
+
+    ok(!present.anonymizedWhenUnnecessary,
+       "anonymized paths are not present when unnecessary. Failed case: " +
+       present.anonymizedWhenUnnecessary);
+    ok(!present.httpWhenAnonymized,
+       "http URLs are anonymized when necessary. Failed case: " +
+       present.httpWhenAnonymized);
+    ok(!present.unanonymizedFilePathWhenAnonymized,
+       "file URLs are anonymized when necessary. Failed case: " +
+       present.unanonymizedFilePathWhenAnonymized);
+
+    runNext();
+  }
+
+  // Reporter registration tests
+
+  // collectReports() calls to the test reporter.
+  let called = 0;
+
+  // The test memory reporter, testing the various report units.
+  // Also acts as a report collector, verifying the reported values match the
+  // expected ones after passing through XPConnect / nsMemoryReporterManager
+  // and back.
+  function MemoryReporterAndCallback() {
+    this.seen = 0;
+  }
+  MemoryReporterAndCallback.prototype = {
+    // The test reports.
+    // Each test key corresponds to the path of the report.  |amount| is a
+    // function called when generating the report.  |expected| is a function
+    // to be tested when receiving a report during collection.  If |expected| is
+    // omitted the |amount| will be checked instead.
+    tests: {
+      "test-memory-reporter-bytes1": {
+        units: BYTES,
+        amount: () => 0
+      },
+      "test-memory-reporter-bytes2": {
+        units: BYTES,
+        amount: () => (1<<30) * 8 // awkward way to say 8G in JS
+      },
+      "test-memory-reporter-counter": {
+        units: COUNT,
+        amount: () => 2
+      },
+      "test-memory-reporter-ccounter": {
+        units: COUNT_CUMULATIVE,
+        amount: () => ++called,
+        expected: () => called
+      },
+      "test-memory-reporter-percentage": {
+        units: PERCENTAGE,
+        amount: () => 9999
+      }
+    },
+    // nsIMemoryReporter
+    collectReports(callback, data, anonymize) {
+      for (let path of Object.keys(this.tests)) {
+        try {
+          let test = this.tests[path];
+          callback.callback(
+            "", // Process. Should be "" initially.
+            path,
+            OTHER,
+            test.units,
+            test.amount(),
+            "Test " + path + ".",
+            data);
+        }
+        catch (ex) {
+          ok(false, ex);
+        }
+      }
+    },
+    // nsIHandleReportCallback
+    callback(process, path, kind, units, amount, data) {
+      if (path in this.tests) {
+        this.seen++;
+        let test = this.tests[path];
+        ok(units === test.units, "Test reporter units match");
+        ok(amount === (test.expected || test.amount)(),
+           "Test reporter values match: " + amount);
+      }
+    },
+    // Checks that the callback has seen the expected number of reports, and
+    // resets the callback counter.
+    // @param expected  Optional.  Expected number of reports the callback
+    //                  should have processed.
+    finish(expected) {
+      if (expected === undefined) {
+        expected = Object.keys(this.tests).length;
+      }
+      is(expected, this.seen,
+         "Test reporter called the correct number of times: " + expected);
+      this.seen = 0;
+    }
+  };
+
+  // General memory reporter + registerStrongReporter tests.
+  function test_register_strong() {
+    let reporterAndCallback = new MemoryReporterAndCallback();
+    // Registration works.
+    mgr.registerStrongReporter(reporterAndCallback);
+
+    // Check the generated reports.
+    mgr.getReports(reporterAndCallback, null,
+      () => {
+        reporterAndCallback.finish();
+        window.setTimeout(test_unregister_strong, 0, reporterAndCallback);
+      }, null,
+      /* anonymize = */ false);
+  }
+
+  function test_unregister_strong(aReporterAndCallback)
+  {
+    mgr.unregisterStrongReporter(aReporterAndCallback);
+
+    // The reporter was unregistered, hence there shouldn't be any reports from
+    // the test reporter.
+    mgr.getReports(aReporterAndCallback, null,
+      () => {
+        aReporterAndCallback.finish(0);
+        runNext();
+      }, null,
+      /* anonymize = */ false);
+  }
+
+  // Check that you cannot register JS components as weak reporters.
+  function test_register_weak() {
+    let reporterAndCallback = new MemoryReporterAndCallback();
+    try {
+      // Should fail! nsMemoryReporterManager will only hold a raw pointer to
+      // "weak" reporters.  When registering a weak reporter, XPConnect will
+      // create a WrappedJS for JS components.  This WrappedJS would be
+      // successfully registered with the manager, only to be destroyed
+      // immediately after, which would eventually lead to a crash when
+      // collecting the reports.  Therefore nsMemoryReporterManager should
+      // reject WrappedJS reporters, which is what is tested here.
+      // See bug 950391 comment #0.
+      mgr.registerWeakReporter(reporterAndCallback);
+      ok(false, "Shouldn't be allowed to register a JS component (WrappedJS)");
+    }
+    catch (ex) {
+      ok(ex.message.includes("NS_ERROR_"),
+         "WrappedJS reporter got rejected: " + ex);
+    }
+
+    runNext();
+  }
+
+  // Kick-off the async tests.
+  runNext();
+
+  ]]>
+  </script>
+</window>
diff --git a/toolkit/components/aboutmemory/tests/test_memoryReporters2.xhtml b/toolkit/components/aboutmemory/tests/test_memoryReporters2.xhtml
new file mode 100644
index 0000000000..b7251c4e62
--- /dev/null
+++ b/toolkit/components/aboutmemory/tests/test_memoryReporters2.xhtml
@@ -0,0 +1,116 @@
+<?xml version="1.0"?>
+<?xml-stylesheet href="chrome://global/skin" type="text/css"?>
+<?xml-stylesheet href="chrome://mochikit/content/tests/SimpleTest/test.css"
+                 type="text/css"?>
+<window title="Memory reporters with child processes"
+  xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul">
+  <script src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"/>
+
+  <!-- This file tests (in a rough fashion) whether the memory reporters are
+       producing sensible results in the presence of child processes. -->
+
+  <!-- test results are displayed in the html:body -->
+  <body xmlns="http://www.w3.org/1999/xhtml">
+  </body>
+
+  <!-- test code goes here -->
+  <script type="application/javascript"><![CDATA[
+
+  SimpleTest.waitForExplicitFinish();
+  let socketProcessRunning = 0;
+  if (SpecialPowers.Services.io.socketProcessLaunched) {
+    socketProcessRunning = 1;
+  }
+  let numToOpen = 3;
+  const expectedNumRemotes = numToOpen + socketProcessRunning;
+  let numReady = 0;
+
+  // Create some remote processes, and set up message-passing so that
+  // we know when each child is fully initialized.
+  let remotes = [];
+  SpecialPowers.pushPrefEnv({"set": [["dom.ipc.processCount", 3]]}).then(function() {
+    for (let i = 0; i < numToOpen; i++) {
+      let w = remotes[i] = window.browsingContext.topChromeWindow.open("remote.xhtml", "", "chrome");
+
+      w.addEventListener("load", function loadHandler() {
+        let remoteBrowser = w.document.getElementById("remote");
+        let mm = remoteBrowser.messageManager;
+        mm.addMessageListener("test:ready", function readyHandler() {
+          mm.removeMessageListener("test:ready", readyHandler);
+          numReady++;
+          if (numReady == numToOpen) {
+            // All the remote processes are ready.  Do memory reporting.
+            doReports();
+          }
+        });
+        mm.loadFrameScript("data:," + encodeURI("sendAsyncMessage('test:ready');"), true);
+      }, {once: true});
+    }
+  });
+
+  let mgr = Cc["@mozilla.org/memory-reporter-manager;1"].
+            getService(Ci.nsIMemoryReporterManager);
+
+  function doReports()
+  {
+    let residents = {};
+
+    let handleReport = function(aProcess, aPath, aKind, aUnits, aAmount, aDesc) {
+      if (aProcess.startsWith(`Utility `)) {
+        // The Utility process that runs the ORB JavaScript validator starts on first
+        // idle in the parent process. This makes it notoriously hard to know _if_ it
+        // actually has started. So we bail. See Bug 1813985.
+        return;
+      }
+
+      if (aPath === "resident") {
+        ok(100 * 1000 <= aAmount && aAmount <= 10 * 1000 * 1000 * 1000,
+           "resident is reasonable");
+        residents[aProcess] = aAmount;
+      }
+    }
+
+    let processReports = function() {
+      // First, test a failure case:  calling getReports() before the previous
+      // getReports() has finished should silently abort.  (And the arguments
+      // won't be used.)
+      mgr.getReports(
+        () => ok(false, "handleReport called for nested getReports() call"),
+        null, null, null, /* anonymize = */ false
+      );
+
+      // Close the remote processes.
+      for (let i = 0; i < numToOpen; i++) {
+        remotes[i].close();
+      }
+
+      // Check the results.
+
+      let processes = Object.keys(residents);
+      ok(processes.length == expectedNumRemotes + 1, "correct resident count");
+
+      let numEmptyProcesses = 0, numNonEmptyProcesses = 0;
+      for (let i = 0; i < processes.length; i++) {
+        if (processes[i] == "") {
+          numEmptyProcesses++;
+        } else {
+          ok(processes[i].startsWith("Browser (") || processes[i].startsWith("Web Content (") ||
+             (processes[i].startsWith("Socket (") && socketProcessRunning)
+             || processes[i].startsWith("web (") || processes[i].startsWith("Utility ("),
+             "correct non-empty process name prefix: " + processes[i]);
+          numNonEmptyProcesses++;
+        }
+      }
+      ok(numEmptyProcesses == 1, "correct empty process name count");
+      ok(numNonEmptyProcesses == expectedNumRemotes,
+                                 "correct non-empty process name count");
+
+      SimpleTest.finish();
+    }
+
+    mgr.getReports(handleReport, null, processReports, null,
+                   /* anonymize = */ false);
+  }
+
+  ]]></script>
+</window>
diff --git a/toolkit/components/aboutmemory/tests/test_sqliteMultiReporter.xhtml b/toolkit/components/aboutmemory/tests/test_sqliteMultiReporter.xhtml
new file mode 100644
index 0000000000..206cee5434
--- /dev/null
+++ b/toolkit/components/aboutmemory/tests/test_sqliteMultiReporter.xhtml
@@ -0,0 +1,46 @@
+<?xml version="1.0"?>
+<?xml-stylesheet type="text/css" href="chrome://global/skin"?>
+<?xml-stylesheet type="text/css" href="chrome://mochikit/content/tests/SimpleTest/test.css"?>
+<window title="about:memory"
+        xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul">
+  <script src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"/>
+  <script src="chrome://mochikit/content/tests/SimpleTest/EventUtils.js"></script>
+
+  <!-- test results are displayed in the html:body -->
+  <body xmlns="http://www.w3.org/1999/xhtml"></body>
+
+  <!-- test code goes here -->
+  <script type="application/javascript">
+  <![CDATA[
+
+  // Test for bug 708248, where the SQLite memory multi-reporter was
+  // crashing when a DB was closed.
+
+  // Nb: this test is all JS and chould be done with an xpcshell test,
+  // but all the other memory reporter tests are mochitests, so it's easier
+  // if this one is too.
+
+  SimpleTest.waitForExplicitFinish();
+
+  // Make a fake DB file.
+  let file = SpecialPowers.Services.dirsvc.get("ProfD", Ci.nsIFile);
+  file.append("test_sqliteMultiReporter-fake-DB-tmp.sqlite");
+
+  // Open and close the DB.
+  let db = SpecialPowers.Services.storage.openDatabase(file);
+  db.close();
+
+  // Invoke all the reporters.  The SQLite multi-reporter is among
+  // them.  It shouldn't crash.
+  let mgr = Cc["@mozilla.org/memory-reporter-manager;1"].
+            getService(Ci.nsIMemoryReporterManager);
+  mgr.getReports(function(){}, null,
+    () => {
+      ok(true, "didn't crash");
+      SimpleTest.finish();
+    }, null,
+    /* anonymize = */ false);
+
+  ]]>
+  </script>
+</window>
diff --git a/toolkit/components/aboutmemory/tests/xpcshell/test_gpuprocess.js b/toolkit/components/aboutmemory/tests/xpcshell/test_gpuprocess.js
new file mode 100644
index 0000000000..4a77752b17
--- /dev/null
+++ b/toolkit/components/aboutmemory/tests/xpcshell/test_gpuprocess.js
@@ -0,0 +1,39 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+"use strict";
+
+function run_test() {
+  let gfxInfo = Cc["@mozilla.org/gfx/info;1"].getService(Ci.nsIGfxInfo);
+  let mgr = Cc["@mozilla.org/memory-reporter-manager;1"].getService(
+    Ci.nsIMemoryReporterManager
+  );
+
+  let ok = gfxInfo.controlGPUProcessForXPCShell(true);
+  Assert.equal(ok, true);
+
+  let endTesting = function () {
+    gfxInfo.controlGPUProcessForXPCShell(false);
+    do_test_finished();
+  };
+
+  let foundGPUProcess = false;
+  let onHandleReport = function (
+    aProcess,
+    aPath,
+    aKind,
+    aUnits,
+    aAmount,
+    aDescription
+  ) {
+    if (/GPU \(pid \d+\)/.test(aProcess)) {
+      foundGPUProcess = true;
+    }
+  };
+  let onFinishReporting = function () {
+    Assert.equal(foundGPUProcess, true);
+    endTesting();
+  };
+
+  mgr.getReports(onHandleReport, null, onFinishReporting, null, false);
+  do_test_pending();
+}
diff --git a/toolkit/components/aboutmemory/tests/xpcshell/xpcshell.ini b/toolkit/components/aboutmemory/tests/xpcshell/xpcshell.ini
new file mode 100644
index 0000000000..3a0598bf49
--- /dev/null
+++ b/toolkit/components/aboutmemory/tests/xpcshell/xpcshell.ini
@@ -0,0 +1,5 @@
+[DEFAULT]
+head =
+skip-if = toolkit != 'windows'
+
+[test_gpuprocess.js]