Adding upstream version 115.7.0esr.upstream/115.7.0esrupstream

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

10 files changed, 747 insertions, 0 deletions

diff --git a/modules/libpref/test/unit_ipc/test_existing_prefs.js b/modules/libpref/test/unit_ipc/test_existing_prefs.js
new file mode 100644
index 0000000000..4efce784b0
--- /dev/null
+++ b/modules/libpref/test/unit_ipc/test_existing_prefs.js
@@ -0,0 +1,20 @@
+function isParentProcess() {
+  let appInfo = Cc["@mozilla.org/xre/app-info;1"];
+  return (
+    !appInfo ||
+    Services.appinfo.processType == Ci.nsIXULRuntime.PROCESS_TYPE_DEFAULT
+  );
+}
+
+function run_test() {
+  if (!isParentProcess()) {
+    do_load_child_test_harness();
+
+    var pb = Services.prefs;
+    pb.setBoolPref("Test.IPC.bool.new", true);
+    pb.setIntPref("Test.IPC.int.new", 23);
+    pb.setCharPref("Test.IPC.char.new", "hey");
+
+    run_test_in_child("test_observed_prefs.js");
+  }
+}
diff --git a/modules/libpref/test/unit_ipc/test_initial_prefs.js b/modules/libpref/test/unit_ipc/test_initial_prefs.js
new file mode 100644
index 0000000000..9c5e8991cf
--- /dev/null
+++ b/modules/libpref/test/unit_ipc/test_initial_prefs.js
@@ -0,0 +1,14 @@
+function isParentProcess() {
+  return Services.appinfo.processType == Ci.nsIXULRuntime.PROCESS_TYPE_DEFAULT;
+}
+
+function run_test() {
+  if (!isParentProcess()) {
+    const pb = Services.prefs;
+    pb.setBoolPref("Test.IPC.bool", true);
+    pb.setIntPref("Test.IPC.int", 23);
+    pb.setCharPref("Test.IPC.char", "hey");
+
+    run_test_in_child("test_existing_prefs.js");
+  }
+}
diff --git a/modules/libpref/test/unit_ipc/test_large_pref.js b/modules/libpref/test/unit_ipc/test_large_pref.js
new file mode 100644
index 0000000000..79c1330c36
--- /dev/null
+++ b/modules/libpref/test/unit_ipc/test_large_pref.js
@@ -0,0 +1,104 @@
+/* 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/. */
+
+// Large preferences should not be set in the child process.
+// Non-string preferences are not tested here, because their behavior
+// should not be affected by this filtering.
+//
+
+function isParentProcess() {
+  return Services.appinfo.processType == Ci.nsIXULRuntime.PROCESS_TYPE_DEFAULT;
+}
+
+function makeBuffer(length) {
+  let string = "x";
+  while (string.length < length) {
+    string = string + string;
+  }
+  if (string.length > length) {
+    string = string.substring(length - string.length);
+  }
+  return string;
+}
+
+// from prefapi.h
+const MAX_ADVISABLE_PREF_LENGTH = 4 * 1024;
+
+const largeString = makeBuffer(MAX_ADVISABLE_PREF_LENGTH + 1);
+const smallString = makeBuffer(4);
+
+const testValues = [
+  { name: "None", value: undefined },
+  { name: "Small", value: smallString },
+  { name: "Large", value: largeString },
+];
+
+function prefName(def, user) {
+  return "Test.IPC.default" + def.name + "User" + user.name;
+}
+
+function expectedPrefValue(def, user) {
+  if (user.value) {
+    return user.value;
+  }
+  return def.value;
+}
+
+function run_test() {
+  const pb = Services.prefs;
+  let defaultBranch = pb.getDefaultBranch("");
+
+  let isParent = isParentProcess();
+  if (isParent) {
+    // Preferences with large values will still appear in the shared memory
+    // snapshot that we share with all processes. They should not, however, be
+    // sent with the list of changes on top of the snapshot.
+    //
+    // So, make sure we've generated the initial snapshot before we set the
+    // preference values by launching a child process with an empty test.
+    sendCommand("");
+
+    // Set all combinations of none, small and large, for default and user prefs.
+    for (let def of testValues) {
+      for (let user of testValues) {
+        let currPref = prefName(def, user);
+        if (def.value) {
+          defaultBranch.setCharPref(currPref, def.value);
+        }
+        if (user.value) {
+          pb.setCharPref(currPref, user.value);
+        }
+      }
+    }
+
+    run_test_in_child("test_large_pref.js");
+  }
+
+  // Check that each preference is set or not set, as appropriate.
+  for (let def of testValues) {
+    for (let user of testValues) {
+      if (!def.value && !user.value) {
+        continue;
+      }
+      let pref_name = prefName(def, user);
+      if (isParent || (def.name != "Large" && user.name != "Large")) {
+        Assert.equal(pb.getCharPref(pref_name), expectedPrefValue(def, user));
+      } else {
+        // This is the child, and either the default or user value is
+        // large, so the preference should not be set.
+        let prefExists;
+        try {
+          let val = pb.getCharPref(pref_name);
+          prefExists = val.length > 128;
+        } catch (e) {
+          prefExists = false;
+        }
+        ok(
+          !prefExists,
+          "Pref " + pref_name + " should not be set in the child"
+        );
+      }
+    }
+  }
+}
diff --git a/modules/libpref/test/unit_ipc/test_locked_prefs.js b/modules/libpref/test/unit_ipc/test_locked_prefs.js
new file mode 100644
index 0000000000..037427e495
--- /dev/null
+++ b/modules/libpref/test/unit_ipc/test_locked_prefs.js
@@ -0,0 +1,39 @@
+/* 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/. */
+
+// Locked status should be communicated to children.
+
+function isParentProcess() {
+  return Services.appinfo.processType == Ci.nsIXULRuntime.PROCESS_TYPE_DEFAULT;
+}
+
+function run_test() {
+  const pb = Services.prefs;
+
+  let bprefname = "Test.IPC.locked.bool";
+  let iprefname = "Test.IPC.locked.int";
+  let sprefname = "Test.IPC.locked.string";
+
+  let isParent = isParentProcess();
+  if (isParent) {
+    pb.setBoolPref(bprefname, true);
+    pb.lockPref(bprefname);
+
+    pb.setIntPref(iprefname, true);
+    pb.lockPref(iprefname);
+
+    pb.setStringPref(sprefname, true);
+    pb.lockPref(sprefname);
+    pb.unlockPref(sprefname);
+
+    run_test_in_child("test_locked_prefs.js");
+  }
+
+  ok(pb.prefIsLocked(bprefname), bprefname + " should be locked in the child");
+  ok(pb.prefIsLocked(iprefname), iprefname + " should be locked in the child");
+  ok(
+    !pb.prefIsLocked(sprefname),
+    sprefname + " should be unlocked in the child"
+  );
+}
diff --git a/modules/libpref/test/unit_ipc/test_observed_prefs.js b/modules/libpref/test/unit_ipc/test_observed_prefs.js
new file mode 100644
index 0000000000..9f6984d555
--- /dev/null
+++ b/modules/libpref/test/unit_ipc/test_observed_prefs.js
@@ -0,0 +1,12 @@
+function isParentProcess() {
+  return Services.appinfo.processType == Ci.nsIXULRuntime.PROCESS_TYPE_DEFAULT;
+}
+
+function run_test() {
+  if (!isParentProcess()) {
+    const pb = Services.prefs;
+    Assert.equal(pb.getBoolPref("Test.IPC.bool.new"), true);
+    Assert.equal(pb.getIntPref("Test.IPC.int.new"), 23);
+    Assert.equal(pb.getCharPref("Test.IPC.char.new"), "hey");
+  }
+}
diff --git a/modules/libpref/test/unit_ipc/test_sharedMap.js b/modules/libpref/test/unit_ipc/test_sharedMap.js
new file mode 100644
index 0000000000..c9a001d7a0
--- /dev/null
+++ b/modules/libpref/test/unit_ipc/test_sharedMap.js
@@ -0,0 +1,362 @@
+/* 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/. */
+"use strict";
+
+// This file tests the functionality of the preference service when using a
+// shared memory snapshot. In this configuration, a snapshot of the initial
+// state of the preferences database is made when we first spawn a child
+// process, and changes after that point are stored as entries in a dynamic hash
+// table, on top of the snapshot.
+
+const { XPCShellContentUtils } = ChromeUtils.importESModule(
+  "resource://testing-common/XPCShellContentUtils.sys.mjs"
+);
+
+XPCShellContentUtils.init(this);
+
+let contentPage;
+
+const { prefs } = Services;
+const defaultPrefs = prefs.getDefaultBranch("");
+
+const FRAME_SCRIPT_INIT = `
+  var { prefs } = Services;
+  var defaultPrefs = prefs.getDefaultBranch("");
+`;
+
+function try_(fn) {
+  try {
+    return fn();
+  } catch (e) {
+    return undefined;
+  }
+}
+
+function getPref(pref) {
+  let flags = {
+    locked: try_(() => prefs.prefIsLocked(pref)),
+    hasUser: try_(() => prefs.prefHasUserValue(pref)),
+  };
+
+  switch (prefs.getPrefType(pref)) {
+    case prefs.PREF_INT:
+      return {
+        ...flags,
+        type: "Int",
+        user: try_(() => prefs.getIntPref(pref)),
+        default: try_(() => defaultPrefs.getIntPref(pref)),
+      };
+    case prefs.PREF_BOOL:
+      return {
+        ...flags,
+        type: "Bool",
+        user: try_(() => prefs.getBoolPref(pref)),
+        default: try_(() => defaultPrefs.getBoolPref(pref)),
+      };
+    case prefs.PREF_STRING:
+      return {
+        ...flags,
+        type: "String",
+        user: try_(() => prefs.getStringPref(pref)),
+        default: try_(() => defaultPrefs.getStringPref(pref)),
+      };
+  }
+  return {};
+}
+
+function getPrefs(prefNames) {
+  let result = {};
+  for (let pref of prefNames) {
+    result[pref] = getPref(pref);
+  }
+  result.childList = prefs.getChildList("");
+  return result;
+}
+
+function checkPref(
+  pref,
+  proc,
+  val,
+  type,
+  userVal,
+  defaultVal,
+  expectedFlags = {}
+) {
+  info(`Check "${pref}" ${proc} value`);
+
+  equal(val.type, type, `Expected type for "${pref}"`);
+  equal(val.user, userVal, `Expected user value for "${pref}"`);
+
+  // We only send changes to the content process when they'll make a visible
+  // difference, so ignore content process default values when we have a defined
+  // user value.
+  if (proc !== "content" || val.user === undefined) {
+    equal(val.default, defaultVal, `Expected default value for "${pref}"`);
+  }
+
+  for (let [flag, value] of Object.entries(expectedFlags)) {
+    equal(val[flag], value, `Expected ${flag} value for "${pref}"`);
+  }
+}
+
+function getPrefList() {
+  return prefs.getChildList("");
+}
+
+const TESTS = {
+  "exists.thenDoesNot": {
+    beforeContent(PREF) {
+      prefs.setBoolPref(PREF, true);
+
+      ok(getPrefList().includes(PREF), `Parent list includes "${PREF}"`);
+    },
+    contentStartup(PREF, val, childList) {
+      ok(getPrefList().includes(PREF), `Parent list includes "${PREF}"`);
+      ok(childList.includes(PREF), `Child list includes "${PREF}"`);
+
+      prefs.clearUserPref(PREF);
+      ok(
+        !getPrefList().includes(PREF),
+        `Parent list doesn't include "${PREF}"`
+      );
+    },
+    contentUpdate1(PREF, val, childList) {
+      ok(
+        !getPrefList().includes(PREF),
+        `Parent list doesn't include "${PREF}"`
+      );
+      ok(!childList.includes(PREF), `Child list doesn't include "${PREF}"`);
+
+      prefs.setCharPref(PREF, "foo");
+      ok(getPrefList().includes(PREF), `Parent list includes "${PREF}"`);
+      checkPref(PREF, "parent", getPref(PREF), "String", "foo");
+    },
+    contentUpdate2(PREF, val, childList) {
+      ok(getPrefList().includes(PREF), `Parent list includes "${PREF}"`);
+      ok(childList.includes(PREF), `Child list includes "${PREF}"`);
+
+      checkPref(PREF, "parent", getPref(PREF), "String", "foo");
+      checkPref(PREF, "child", val, "String", "foo");
+    },
+  },
+  "doesNotExists.thenDoes": {
+    contentStartup(PREF, val, childList) {
+      ok(
+        !getPrefList().includes(PREF),
+        `Parent list doesn't include "${PREF}"`
+      );
+      ok(!childList.includes(PREF), `Child list doesn't include "${PREF}"`);
+
+      prefs.setIntPref(PREF, 42);
+      ok(getPrefList().includes(PREF), `Parent list includes "${PREF}"`);
+    },
+    contentUpdate1(PREF, val, childList) {
+      ok(getPrefList().includes(PREF), `Parent list includes "${PREF}"`);
+      ok(childList.includes(PREF), `Child list includes "${PREF}"`);
+
+      checkPref(PREF, "parent", getPref(PREF), "Int", 42);
+      checkPref(PREF, "child", val, "Int", 42);
+    },
+  },
+};
+
+const PREFS = [
+  { type: "Bool", values: [true, false, true] },
+  { type: "Int", values: [24, 42, 73] },
+  { type: "String", values: ["meh", "hem", "hrm"] },
+];
+
+for (let { type, values } of PREFS) {
+  let set = `set${type}Pref`;
+
+  function prefTest(opts) {
+    function check(
+      pref,
+      proc,
+      val,
+      {
+        expectedVal,
+        defaultVal = undefined,
+        expectedDefault = defaultVal,
+        expectedFlags = {},
+      }
+    ) {
+      checkPref(
+        pref,
+        proc,
+        val,
+        type,
+        expectedVal,
+        expectedDefault,
+        expectedFlags
+      );
+    }
+
+    function updatePref(
+      PREF,
+      { userVal = undefined, defaultVal = undefined, flags = {} }
+    ) {
+      info(`Update "${PREF}"`);
+      if (userVal !== undefined) {
+        prefs[set](PREF, userVal);
+      }
+      if (defaultVal !== undefined) {
+        defaultPrefs[set](PREF, defaultVal);
+      }
+      if (flags.locked === true) {
+        prefs.lockPref(PREF);
+      } else if (flags.locked === false) {
+        prefs.unlockPref(PREF);
+      }
+    }
+
+    return {
+      beforeContent(PREF) {
+        updatePref(PREF, opts.initial);
+        check(PREF, "parent", getPref(PREF), opts.initial);
+      },
+      contentStartup(PREF, contentVal) {
+        check(PREF, "content", contentVal, opts.initial);
+        check(PREF, "parent", getPref(PREF), opts.initial);
+
+        updatePref(PREF, opts.change1);
+        check(PREF, "parent", getPref(PREF), opts.change1);
+      },
+      contentUpdate1(PREF, contentVal) {
+        check(PREF, "content", contentVal, opts.change1);
+        check(PREF, "parent", getPref(PREF), opts.change1);
+
+        if (opts.change2) {
+          updatePref(PREF, opts.change2);
+          check(PREF, "parent", getPref(PREF), opts.change2);
+        }
+      },
+      contentUpdate2(PREF, contentVal) {
+        if (opts.change2) {
+          check(PREF, "content", contentVal, opts.change2);
+          check(PREF, "parent", getPref(PREF), opts.change2);
+        }
+      },
+    };
+  }
+
+  for (let i of [0, 1]) {
+    let userVal = values[i];
+    let defaultVal = values[+!i];
+
+    TESTS[`type.${type}.${i}.default`] = prefTest({
+      initial: { defaultVal, expectedVal: defaultVal },
+      change1: { defaultVal: values[2], expectedVal: values[2] },
+    });
+
+    TESTS[`type.${type}.${i}.user`] = prefTest({
+      initial: { userVal, expectedVal: userVal },
+      change1: { defaultVal: values[2], expectedVal: userVal },
+      change2: {
+        userVal: values[2],
+        expectedDefault: values[2],
+        expectedVal: values[2],
+      },
+    });
+
+    TESTS[`type.${type}.${i}.both`] = prefTest({
+      initial: { userVal, defaultVal, expectedVal: userVal },
+      change1: { defaultVal: values[2], expectedVal: userVal },
+      change2: {
+        userVal: values[2],
+        expectedDefault: values[2],
+        expectedVal: values[2],
+      },
+    });
+
+    TESTS[`type.${type}.${i}.both.thenLock`] = prefTest({
+      initial: { userVal, defaultVal, expectedVal: userVal },
+      change1: {
+        expectedDefault: defaultVal,
+        expectedVal: defaultVal,
+        flags: { locked: true },
+        expectFlags: { locked: true },
+      },
+    });
+
+    TESTS[`type.${type}.${i}.both.thenUnlock`] = prefTest({
+      initial: {
+        userVal,
+        defaultVal,
+        expectedVal: defaultVal,
+        flags: { locked: true },
+        expectedFlags: { locked: true },
+      },
+      change1: {
+        expectedDefault: defaultVal,
+        expectedVal: userVal,
+        flags: { locked: false },
+        expectFlags: { locked: false },
+      },
+    });
+
+    TESTS[`type.${type}.${i}.both.locked`] = prefTest({
+      initial: {
+        userVal,
+        defaultVal,
+        expectedVal: defaultVal,
+        flags: { locked: true },
+        expectedFlags: { locked: true },
+      },
+      change1: {
+        userVal: values[2],
+        expectedDefault: defaultVal,
+        expectedVal: defaultVal,
+        expectedFlags: { locked: true },
+      },
+      change2: {
+        defaultVal: values[2],
+        expectedDefault: defaultVal,
+        expectedVal: defaultVal,
+        expectedFlags: { locked: true },
+      },
+    });
+  }
+}
+
+add_task(async function test_sharedMap_prefs() {
+  let prefValues = {};
+
+  async function runChecks(op) {
+    for (let [pref, ops] of Object.entries(TESTS)) {
+      if (ops[op]) {
+        info(`Running ${op} for "${pref}"`);
+        await ops[op](
+          pref,
+          prefValues[pref] || undefined,
+          prefValues.childList || undefined
+        );
+      }
+    }
+  }
+
+  await runChecks("beforeContent");
+
+  contentPage = await XPCShellContentUtils.loadContentPage("about:blank", {
+    remote: true,
+  });
+  registerCleanupFunction(() => contentPage.close());
+
+  contentPage.addFrameScriptHelper(FRAME_SCRIPT_INIT);
+  contentPage.addFrameScriptHelper(try_);
+  contentPage.addFrameScriptHelper(getPref);
+
+  let prefNames = Object.keys(TESTS);
+  prefValues = await contentPage.legacySpawn(prefNames, getPrefs);
+
+  await runChecks("contentStartup");
+
+  prefValues = await contentPage.legacySpawn(prefNames, getPrefs);
+
+  await runChecks("contentUpdate1");
+
+  prefValues = await contentPage.legacySpawn(prefNames, getPrefs);
+
+  await runChecks("contentUpdate2");
+});
diff --git a/modules/libpref/test/unit_ipc/test_sharedMap_static_prefs.js b/modules/libpref/test/unit_ipc/test_sharedMap_static_prefs.js
new file mode 100644
index 0000000000..a8181bf2cb
--- /dev/null
+++ b/modules/libpref/test/unit_ipc/test_sharedMap_static_prefs.js
@@ -0,0 +1,76 @@
+/* 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/. */
+"use strict";
+
+// Tests that static preferences in the content process
+// correctly handle values which are different from their
+// statically-defined defaults.
+//
+// Since we can't access static preference values from JS, this tests relies on
+// assertions in debug builds to detect mismatches. The default and user
+// values of two preferences are changed (respectively) before a content
+// process is started. Once the content process is launched, the
+// preference service asserts that the values stored in all static prefs
+// match their current values as known to the preference service. If
+// there's a mismatch, the shell will crash, and the test will fail.
+//
+// For sanity, we also check that the dynamically retrieved preference
+// values in the content process match our expectations, though this is
+// not strictly part of the test.
+
+const PREF1_NAME = "dom.webcomponents.shadowdom.report_usage";
+const PREF1_VALUE = false;
+
+const PREF2_NAME = "dom.mutation-events.cssom.disabled";
+const PREF2_VALUE = true;
+
+const { XPCShellContentUtils } = ChromeUtils.importESModule(
+  "resource://testing-common/XPCShellContentUtils.sys.mjs"
+);
+
+XPCShellContentUtils.init(this);
+
+const { prefs } = Services;
+const defaultPrefs = prefs.getDefaultBranch("");
+
+add_task(async function test_sharedMap_static_prefs() {
+  equal(
+    prefs.getBoolPref(PREF1_NAME),
+    PREF1_VALUE,
+    `Expected initial value for ${PREF1_NAME}`
+  );
+  equal(
+    prefs.getBoolPref(PREF2_NAME),
+    PREF2_VALUE,
+    `Expected initial value for ${PREF2_NAME}`
+  );
+
+  defaultPrefs.setBoolPref(PREF1_NAME, !PREF1_VALUE);
+  prefs.setBoolPref(PREF2_NAME, !PREF2_VALUE);
+
+  equal(
+    prefs.getBoolPref(PREF1_NAME),
+    !PREF1_VALUE,
+    `Expected updated value for ${PREF1_NAME}`
+  );
+  equal(
+    prefs.getBoolPref(PREF2_NAME),
+    !PREF2_VALUE,
+    `Expected updated value for ${PREF2_NAME}`
+  );
+
+  let contentPage = await XPCShellContentUtils.loadContentPage("about:blank", {
+    remote: true,
+  });
+  registerCleanupFunction(() => contentPage.close());
+
+  /* eslint-disable no-shadow */
+  let values = await contentPage.spawn([[PREF1_NAME, PREF2_NAME]], prefs => {
+    return prefs.map(pref => Services.prefs.getBoolPref(pref));
+  });
+  /* eslint-enable no-shadow */
+
+  equal(values[0], !PREF1_VALUE, `Expected content value for ${PREF1_NAME}`);
+  equal(values[1], !PREF2_VALUE, `Expected content value for ${PREF2_NAME}`);
+});
diff --git a/modules/libpref/test/unit_ipc/test_update_prefs.js b/modules/libpref/test/unit_ipc/test_update_prefs.js
new file mode 100644
index 0000000000..51e2c458c5
--- /dev/null
+++ b/modules/libpref/test/unit_ipc/test_update_prefs.js
@@ -0,0 +1,34 @@
+function isParentProcess() {
+  return Services.appinfo.processType == Ci.nsIXULRuntime.PROCESS_TYPE_DEFAULT;
+}
+
+function run_test() {
+  if (isParentProcess()) {
+    do_load_child_test_harness();
+
+    var pb = Services.prefs;
+
+    // these prefs are set after the child has been created.
+    pb.setBoolPref("Test.IPC.bool.new", true);
+    pb.setIntPref("Test.IPC.int.new", 23);
+    pb.setCharPref("Test.IPC.char.new", "hey");
+
+    run_test_in_child("test_observed_prefs.js", testPrefClear);
+  }
+}
+
+function testPrefClear() {
+  var pb = Services.prefs;
+  pb.clearUserPref("Test.IPC.bool.new");
+
+  sendCommand(
+    'var pb = Cc["@mozilla.org/preferences-service;1"].getService(Ci.nsIPrefBranch);\n' +
+      'pb.prefHasUserValue("Test.IPC.bool.new");\n',
+    checkWasCleared
+  );
+}
+
+function checkWasCleared(existsStr) {
+  Assert.equal(existsStr, "false");
+  do_test_finished();
+}
diff --git a/modules/libpref/test/unit_ipc/test_user_default_prefs.js b/modules/libpref/test/unit_ipc/test_user_default_prefs.js
new file mode 100644
index 0000000000..3307522513
--- /dev/null
+++ b/modules/libpref/test/unit_ipc/test_user_default_prefs.js
@@ -0,0 +1,72 @@
+const pb = Services.prefs;
+
+// This pref is chosen somewhat arbitrarily --- we just need one
+// that's guaranteed to have a default value.
+const kPrefName = "intl.accept_languages"; // of type char, which we
+// assume below
+var initialValue = null;
+
+function check_child_pref_info_eq(continuation) {
+  sendCommand(
+    'var pb = Components.classes["@mozilla.org/preferences-service;1"].getService(Components.interfaces.nsIPrefBranch);\n' +
+      // Returns concatenation "[value],[isUser]"
+      'pb.getCharPref("' +
+      kPrefName +
+      '")+ "," +' +
+      'pb.prefHasUserValue("' +
+      kPrefName +
+      '");',
+    function (info) {
+      let [value, isUser] = info.split(",");
+      Assert.equal(pb.getCharPref(kPrefName), value);
+      Assert.equal(pb.prefHasUserValue(kPrefName), isUser == "true");
+      continuation();
+    }
+  );
+}
+
+function run_test() {
+  // We finish in clean_up()
+  do_test_pending();
+
+  initialValue = pb.getCharPref(kPrefName);
+
+  test_user_setting();
+}
+
+function test_user_setting() {
+  // We rely on setting this before the content process starts up.
+  // When it starts up, it should recognize this as a user pref, not
+  // a default pref.
+  pb.setCharPref(kPrefName, "i-imaginarylanguage");
+  // NB: processing of the value-change notification in the child
+  // process triggered by the above set happens-before the remaining
+  // code here
+  check_child_pref_info_eq(function () {
+    Assert.equal(pb.prefHasUserValue(kPrefName), true);
+
+    test_cleared_is_default();
+  });
+}
+
+function test_cleared_is_default() {
+  pb.clearUserPref(kPrefName);
+  // NB: processing of the value-change notification in the child
+  // process triggered by the above set happens-before the remaining
+  // code here
+  check_child_pref_info_eq(function () {
+    Assert.equal(pb.prefHasUserValue(kPrefName), false);
+
+    clean_up();
+  });
+}
+
+function clean_up() {
+  pb.setCharPref(kPrefName, initialValue);
+  // NB: processing of the value-change notification in the child
+  // process triggered by the above set happens-before the remaining
+  // code here
+  check_child_pref_info_eq(function () {
+    do_test_finished();
+  });
+}
diff --git a/modules/libpref/test/unit_ipc/xpcshell.ini b/modules/libpref/test/unit_ipc/xpcshell.ini
new file mode 100644
index 0000000000..e2a444f774
--- /dev/null
+++ b/modules/libpref/test/unit_ipc/xpcshell.ini
@@ -0,0 +1,14 @@
+[DEFAULT]
+head =
+skip-if = toolkit == 'android'
+
+[test_existing_prefs.js]
+[test_initial_prefs.js]
+[test_large_pref.js]
+[test_locked_prefs.js]
+[test_observed_prefs.js]
+[test_update_prefs.js]
+[test_sharedMap.js]
+[test_sharedMap_static_prefs.js]
+skip-if = !debug # Relies on debug assertions to catch failure cases.
+[test_user_default_prefs.js]