Adding upstream version 115.7.0esr.upstream/115.7.0esrupstream

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

52 files changed, 14378 insertions, 0 deletions

diff --git a/services/common/app_services_logger/AppServicesLoggerComponents.h b/services/common/app_services_logger/AppServicesLoggerComponents.h
new file mode 100644
index 0000000000..015eae230b
--- /dev/null
+++ b/services/common/app_services_logger/AppServicesLoggerComponents.h
@@ -0,0 +1,38 @@
+/* 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/. */
+
+#ifndef mozilla_services_AppServicesLoggerComponents_h_
+#define mozilla_services_AppServicesLoggerComponents_h_
+
+#include "mozIAppServicesLogger.h"
+#include "nsCOMPtr.h"
+
+extern "C" {
+
+// Implemented in Rust, in the `app_services_logger` crate.
+nsresult NS_NewAppServicesLogger(mozIAppServicesLogger** aResult);
+
+}  // extern "C"
+
+namespace mozilla {
+namespace appservices {
+
+// The C++ constructor for a `services.appServicesLogger` service. This wrapper
+// exists because `components.conf` requires a component class constructor to
+// return an `already_AddRefed<T>`, but Rust doesn't have such a type. So we
+// call the Rust constructor using a `nsCOMPtr` (which is compatible with Rust's
+// `xpcom::RefPtr`) out param, and return that.
+already_AddRefed<mozIAppServicesLogger> NewLogService() {
+  nsCOMPtr<mozIAppServicesLogger> logger;
+  nsresult rv = NS_NewAppServicesLogger(getter_AddRefs(logger));
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return nullptr;
+  }
+  return logger.forget();
+}
+
+}  // namespace appservices
+}  // namespace mozilla
+
+#endif  // mozilla_services_AppServicesLoggerComponents_h_
diff --git a/services/common/app_services_logger/Cargo.toml b/services/common/app_services_logger/Cargo.toml
new file mode 100644
index 0000000000..d68c378845
--- /dev/null
+++ b/services/common/app_services_logger/Cargo.toml
@@ -0,0 +1,17 @@
+[package]
+name = "app_services_logger"
+version = "0.1.0"
+authors = ["lougeniac64 <lougeniaC64@users.noreply.github.com>"]
+edition = "2018"
+license = "MPL-2.0"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+cstr = "0.2"
+golden_gate = { path = "../../../services/sync/golden_gate" }
+log = "0.4"
+once_cell = "1.4.0"
+nserror = { path = "../../../xpcom/rust/nserror" }
+nsstring = { path = "../../../xpcom/rust/nsstring" }
+xpcom = { path = "../../../xpcom/rust/xpcom" }
diff --git a/services/common/app_services_logger/components.conf b/services/common/app_services_logger/components.conf
new file mode 100644
index 0000000000..cdea60a04b
--- /dev/null
+++ b/services/common/app_services_logger/components.conf
@@ -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/.
+
+Classes = [
+    {
+        'cid': '{d2716568-f5fa-4989-91dd-e11599e932a1}',
+        'contract_ids': ['@mozilla.org/appservices/logger;1'],
+        'type': 'mozIAppServicesLogger',
+        'headers': ['mozilla/appservices/AppServicesLoggerComponents.h'],
+        'constructor': 'mozilla::appservices::NewLogService',
+    },
+]
diff --git a/services/common/app_services_logger/src/lib.rs b/services/common/app_services_logger/src/lib.rs
new file mode 100644
index 0000000000..0ad96a782a
--- /dev/null
+++ b/services/common/app_services_logger/src/lib.rs
@@ -0,0 +1,135 @@
+/* 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 https://mozilla.org/MPL/2.0/. */
+
+//! This provides a XPCOM service to send app services logs to the desktop
+
+#[macro_use]
+extern crate cstr;
+
+#[macro_use]
+extern crate xpcom;
+
+use golden_gate::log::LogSink;
+use log;
+use nserror::{nsresult, NS_OK};
+use nsstring::nsAString;
+use once_cell::sync::Lazy;
+use std::os::raw::c_char;
+use std::{
+    cmp,
+    collections::HashMap,
+    sync::{
+        atomic::{AtomicBool, Ordering},
+        RwLock,
+    },
+};
+use xpcom::{
+    interfaces::{mozIAppServicesLogger, mozIServicesLogSink, nsIObserverService, nsISupports},
+    RefPtr,
+};
+
+/// A flag that's set after we register our observer to clear the map of loggers
+/// on shutdown.
+static SHUTDOWN_OBSERVED: AtomicBool = AtomicBool::new(false);
+
+#[xpcom(implement(mozIAppServicesLogger), nonatomic)]
+pub struct AppServicesLogger {}
+
+pub static LOGGERS_BY_TARGET: Lazy<RwLock<HashMap<String, LogSink>>> = Lazy::new(|| {
+    let h: HashMap<String, LogSink> = HashMap::new();
+    let m = RwLock::new(h);
+    m
+});
+
+impl AppServicesLogger {
+    xpcom_method!(register => Register(target: *const nsAString, logger: *const mozIServicesLogSink));
+    fn register(&self, target: &nsAString, logger: &mozIServicesLogSink) -> Result<(), nsresult> {
+        let log_sink_logger = LogSink::with_logger(Some(logger))?;
+        let max_level = cmp::max(log::max_level(), log_sink_logger.max_level);
+
+        // Note: This will only work if the max_level is lower than the compile-time
+        // max_level_* filter.
+        log::set_max_level(max_level);
+
+        ensure_observing_shutdown();
+
+        LOGGERS_BY_TARGET
+            .write()
+            .unwrap()
+            .insert(target.to_string(), log_sink_logger);
+        Ok(())
+    }
+
+    pub fn is_app_services_logger_registered(target: String) -> bool {
+        match LOGGERS_BY_TARGET.read() {
+            Ok(loggers_by_target) => loggers_by_target.contains_key(&target),
+            Err(_e) => false,
+        }
+    }
+}
+
+// Import the `NS_IsMainThread` symbol from Gecko...
+extern "C" {
+    fn NS_IsMainThread() -> bool;
+}
+
+/// Registers an observer to clear the loggers map on `xpcom-shutdown`. This
+/// function must be called from the main thread, because the observer service
+//// is main thread-only.
+fn ensure_observing_shutdown() {
+    assert!(unsafe { NS_IsMainThread() });
+    // If we've already registered our observer, bail. Relaxed ordering is safe
+    // here and below, because we've asserted we're only called from the main
+    // thread, and only check the flag here.
+    if SHUTDOWN_OBSERVED.load(Ordering::Relaxed) {
+        return;
+    }
+    if let Ok(service) = xpcom::components::Observer::service::<nsIObserverService>() {
+        let observer = ShutdownObserver::allocate(InitShutdownObserver {});
+        let rv = unsafe {
+            service.AddObserver(observer.coerce(), cstr!("xpcom-shutdown").as_ptr(), false)
+        };
+        // If we fail to register the observer now, or fail to get the observer
+        // service, the flag will remain `false`, and we'll try again on the
+        // next call to `ensure_observing_shutdown`.
+        SHUTDOWN_OBSERVED.store(rv.succeeded(), Ordering::Relaxed);
+    }
+}
+
+#[xpcom(implement(nsIObserver), nonatomic)]
+struct ShutdownObserver {}
+
+impl ShutdownObserver {
+    xpcom_method!(observe => Observe(_subject: *const nsISupports, topic: *const c_char, _data: *const u16));
+    /// Remove our shutdown observer and clear the map.
+    fn observe(
+        &self,
+        _subject: &nsISupports,
+        topic: *const c_char,
+        _data: *const u16,
+    ) -> Result<(), nsresult> {
+        LOGGERS_BY_TARGET.write().unwrap().clear();
+        if let Ok(service) = xpcom::components::Observer::service::<nsIObserverService>() {
+            // Ignore errors, since we're already shutting down.
+            let _ = unsafe { service.RemoveObserver(self.coerce(), topic) };
+        }
+        Ok(())
+    }
+}
+
+/// The constructor for an `AppServicesLogger` service. This uses C linkage so that it
+/// can be called from C++. See `AppServicesLoggerComponents.h` for the C++
+/// constructor that's passed to the component manager.
+///
+/// # Safety
+///
+/// This function is unsafe because it dereferences `result`.
+#[no_mangle]
+pub unsafe extern "C" fn NS_NewAppServicesLogger(
+    result: *mut *const mozIAppServicesLogger,
+) -> nsresult {
+    let logger = AppServicesLogger::allocate(InitAppServicesLogger {});
+    RefPtr::new(logger.coerce::<mozIAppServicesLogger>()).forget(&mut *result);
+    NS_OK
+}
diff --git a/services/common/async.sys.mjs b/services/common/async.sys.mjs
new file mode 100644
index 0000000000..564b46a071
--- /dev/null
+++ b/services/common/async.sys.mjs
@@ -0,0 +1,301 @@
+/* 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/. */
+
+const Timer = Components.Constructor("@mozilla.org/timer;1", "nsITimer");
+
+/*
+ * Helpers for various async operations.
+ */
+export var Async = {
+  /**
+   * Execute an arbitrary number of asynchronous functions one after the
+   * other, passing the callback arguments on to the next one.  All functions
+   * must take a callback function as their last argument.  The 'this' object
+   * will be whatever chain()'s is.
+   *
+   * @usage this._chain = Async.chain;
+   *        this._chain(this.foo, this.bar, this.baz)(args, for, foo)
+   *
+   * This is equivalent to:
+   *
+   *   let self = this;
+   *   self.foo(args, for, foo, function (bars, args) {
+   *     self.bar(bars, args, function (baz, params) {
+   *       self.baz(baz, params);
+   *     });
+   *   });
+   */
+  chain: function chain(...funcs) {
+    let thisObj = this;
+    return function callback() {
+      if (funcs.length) {
+        let args = [...arguments, callback];
+        let f = funcs.shift();
+        f.apply(thisObj, args);
+      }
+    };
+  },
+
+  /**
+   * Check if the app is still ready (not quitting). Returns true, or throws an
+   * exception if not ready.
+   */
+  checkAppReady: function checkAppReady() {
+    // Watch for app-quit notification to stop any sync calls
+    Services.obs.addObserver(function onQuitApplication() {
+      Services.obs.removeObserver(onQuitApplication, "quit-application");
+      Async.checkAppReady = Async.promiseYield = function () {
+        let exception = Components.Exception(
+          "App. Quitting",
+          Cr.NS_ERROR_ABORT
+        );
+        exception.appIsShuttingDown = true;
+        throw exception;
+      };
+    }, "quit-application");
+    // In the common case, checkAppReady just returns true
+    return (Async.checkAppReady = function () {
+      return true;
+    })();
+  },
+
+  /**
+   * Check if the app is still ready (not quitting). Returns true if the app
+   * is ready, or false if it is being shut down.
+   */
+  isAppReady() {
+    try {
+      return Async.checkAppReady();
+    } catch (ex) {
+      if (!Async.isShutdownException(ex)) {
+        throw ex;
+      }
+    }
+    return false;
+  },
+
+  /**
+   * Check if the passed exception is one raised by checkAppReady. Typically
+   * this will be used in exception handlers to allow such exceptions to
+   * make their way to the top frame and allow the app to actually terminate.
+   */
+  isShutdownException(exception) {
+    return exception && exception.appIsShuttingDown === true;
+  },
+
+  /**
+   * A "tight loop" of promises can still lock up the browser for some time.
+   * Periodically waiting for a promise returned by this function will solve
+   * that.
+   * You should probably not use this method directly and instead use jankYielder
+   * below.
+   * Some reference here:
+   * - https://gist.github.com/jesstelford/bbb30b983bddaa6e5fef2eb867d37678
+   * - https://bugzilla.mozilla.org/show_bug.cgi?id=1094248
+   */
+  promiseYield() {
+    return new Promise(resolve => {
+      Services.tm.currentThread.dispatch(resolve, Ci.nsIThread.DISPATCH_NORMAL);
+    });
+  },
+
+  /**
+   * Shared state for yielding every N calls.
+   *
+   * Can be passed to multiple Async.yieldingForEach to have them overall yield
+   * every N iterations.
+   */
+  yieldState(yieldEvery = 50) {
+    let iterations = 0;
+
+    return {
+      shouldYield() {
+        ++iterations;
+        return iterations % yieldEvery === 0;
+      },
+    };
+  },
+
+  /**
+   * Apply the given function to each element of the iterable, yielding the
+   * event loop every yieldEvery iterations.
+   *
+   * @param iterable {Iterable}
+   *        The iterable or iterator to iterate through.
+   *
+   * @param fn {(*) -> void|boolean}
+   *        The function to be called on each element of the iterable.
+   *
+   *        Returning true from the function will stop the iteration.
+   *
+   * @param [yieldEvery = 50] {number|object}
+   *        The number of iterations to complete before yielding back to the event
+   *        loop.
+   *
+   * @return {boolean}
+   *         Whether or not the function returned early.
+   */
+  async yieldingForEach(iterable, fn, yieldEvery = 50) {
+    const yieldState =
+      typeof yieldEvery === "number"
+        ? Async.yieldState(yieldEvery)
+        : yieldEvery;
+    let iteration = 0;
+
+    for (const item of iterable) {
+      let result = fn(item, iteration++);
+      if (typeof result !== "undefined" && typeof result.then !== "undefined") {
+        // If we await result when it is not a Promise, we create an
+        // automatically resolved promise, which is exactly the case that we
+        // are trying to avoid.
+        result = await result;
+      }
+
+      if (result === true) {
+        return true;
+      }
+
+      if (yieldState.shouldYield()) {
+        await Async.promiseYield();
+        Async.checkAppReady();
+      }
+    }
+
+    return false;
+  },
+
+  asyncQueueCaller(log) {
+    return new AsyncQueueCaller(log);
+  },
+
+  asyncObserver(log, obj) {
+    return new AsyncObserver(log, obj);
+  },
+
+  watchdog() {
+    return new Watchdog();
+  },
+};
+
+/**
+ * Allows consumers to enqueue asynchronous callbacks to be called in order.
+ * Typically this is used when providing a callback to a caller that doesn't
+ * await on promises.
+ */
+class AsyncQueueCaller {
+  constructor(log) {
+    this._log = log;
+    this._queue = Promise.resolve();
+    this.QueryInterface = ChromeUtils.generateQI([
+      "nsIObserver",
+      "nsISupportsWeakReference",
+    ]);
+  }
+
+  /**
+   * /!\ Never await on another function that calls enqueueCall /!\
+   *     on the same queue or we will deadlock.
+   */
+  enqueueCall(func) {
+    this._queue = (async () => {
+      await this._queue;
+      try {
+        return await func();
+      } catch (e) {
+        this._log.error(e);
+        return false;
+      }
+    })();
+  }
+
+  promiseCallsComplete() {
+    return this._queue;
+  }
+}
+
+/*
+ * Subclass of AsyncQueueCaller that can be used with Services.obs directly.
+ * When this observe() is called, it will enqueue a call to the consumers's
+ * observe().
+ */
+class AsyncObserver extends AsyncQueueCaller {
+  constructor(obj, log) {
+    super(log);
+    this.obj = obj;
+  }
+
+  observe(subject, topic, data) {
+    this.enqueueCall(() => this.obj.observe(subject, topic, data));
+  }
+
+  promiseObserversComplete() {
+    return this.promiseCallsComplete();
+  }
+}
+
+/**
+ * Woof! Signals an operation to abort, either at shutdown or after a timeout.
+ * The buffered engine uses this to abort long-running merges, so that they
+ * don't prevent Firefox from quitting, or block future syncs.
+ */
+class Watchdog {
+  constructor() {
+    this.controller = new AbortController();
+    this.timer = new Timer();
+
+    /**
+     * The reason for signaling an abort. `null` if not signaled,
+     * `"timeout"` if the watchdog timer fired, or `"shutdown"` if the app is
+     * is quitting.
+     *
+     * @type {String?}
+     */
+    this.abortReason = null;
+  }
+
+  /**
+   * Returns the abort signal for this watchdog. This can be passed to APIs
+   * that take a signal for cancellation, like `SyncedBookmarksMirror::apply`
+   * or `fetch`.
+   *
+   * @type {AbortSignal}
+   */
+  get signal() {
+    return this.controller.signal;
+  }
+
+  /**
+   * Starts the watchdog timer, and listens for the app quitting.
+   *
+   * @param {Number} delay
+   *                 The time to wait before signaling the operation to abort.
+   */
+  start(delay) {
+    if (!this.signal.aborted) {
+      Services.obs.addObserver(this, "quit-application");
+      this.timer.init(this, delay, Ci.nsITimer.TYPE_ONE_SHOT);
+    }
+  }
+
+  /**
+   * Stops the watchdog timer and removes any listeners. This should be called
+   * after the operation finishes.
+   */
+  stop() {
+    if (!this.signal.aborted) {
+      Services.obs.removeObserver(this, "quit-application");
+      this.timer.cancel();
+    }
+  }
+
+  observe(subject, topic, data) {
+    if (topic == "timer-callback") {
+      this.abortReason = "timeout";
+    } else if (topic == "quit-application") {
+      this.abortReason = "shutdown";
+    }
+    this.stop();
+    this.controller.abort();
+  }
+}
diff --git a/services/common/hawkclient.sys.mjs b/services/common/hawkclient.sys.mjs
new file mode 100644
index 0000000000..4e45ad13ee
--- /dev/null
+++ b/services/common/hawkclient.sys.mjs
@@ -0,0 +1,337 @@
+/* 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/. */
+
+/*
+ * HAWK is an HTTP authentication scheme using a message authentication code
+ * (MAC) algorithm to provide partial HTTP request cryptographic verification.
+ *
+ * For details, see: https://github.com/hueniverse/hawk
+ *
+ * With HAWK, it is essential that the clocks on clients and server not have an
+ * absolute delta of greater than one minute, as the HAWK protocol uses
+ * timestamps to reduce the possibility of replay attacks.  However, it is
+ * likely that some clients' clocks will be more than a little off, especially
+ * in mobile devices, which would break HAWK-based services (like sync and
+ * firefox accounts) for those clients.
+ *
+ * This library provides a stateful HAWK client that calculates (roughly) the
+ * clock delta on the client vs the server.  The library provides an interface
+ * for deriving HAWK credentials and making HAWK-authenticated REST requests to
+ * a single remote server.  Therefore, callers who want to interact with
+ * multiple HAWK services should instantiate one HawkClient per service.
+ */
+
+import { HAWKAuthenticatedRESTRequest } from "resource://services-common/hawkrequest.sys.mjs";
+
+import { Observers } from "resource://services-common/observers.sys.mjs";
+import { Log } from "resource://gre/modules/Log.sys.mjs";
+import { XPCOMUtils } from "resource://gre/modules/XPCOMUtils.sys.mjs";
+
+// log.appender.dump should be one of "Fatal", "Error", "Warn", "Info", "Config",
+// "Debug", "Trace" or "All". If none is specified, "Error" will be used by
+// default.
+// Note however that Sync will also add this log to *its* DumpAppender, so
+// in a Sync context it shouldn't be necessary to adjust this - however, that
+// also means error logs are likely to be dump'd twice but that's OK.
+const PREF_LOG_LEVEL = "services.common.hawk.log.appender.dump";
+
+// A pref that can be set so "sensitive" information (eg, personally
+// identifiable info, credentials, etc) will be logged.
+const PREF_LOG_SENSITIVE_DETAILS = "services.common.hawk.log.sensitive";
+
+const lazy = {};
+
+XPCOMUtils.defineLazyGetter(lazy, "log", function () {
+  let log = Log.repository.getLogger("Hawk");
+  // We set the log itself to "debug" and set the level from the preference to
+  // the appender.  This allows other things to send the logs to different
+  // appenders, while still allowing the pref to control what is seen via dump()
+  log.level = Log.Level.Debug;
+  let appender = new Log.DumpAppender();
+  log.addAppender(appender);
+  appender.level = Log.Level.Error;
+  try {
+    let level =
+      Services.prefs.getPrefType(PREF_LOG_LEVEL) ==
+        Ci.nsIPrefBranch.PREF_STRING &&
+      Services.prefs.getCharPref(PREF_LOG_LEVEL);
+    appender.level = Log.Level[level] || Log.Level.Error;
+  } catch (e) {
+    log.error(e);
+  }
+
+  return log;
+});
+
+// A boolean to indicate if personally identifiable information (or anything
+// else sensitive, such as credentials) should be logged.
+XPCOMUtils.defineLazyGetter(lazy, "logPII", function () {
+  try {
+    return Services.prefs.getBoolPref(PREF_LOG_SENSITIVE_DETAILS);
+  } catch (_) {
+    return false;
+  }
+});
+
+/*
+ * A general purpose client for making HAWK authenticated requests to a single
+ * host.  Keeps track of the clock offset between the client and the host for
+ * computation of the timestamp in the HAWK Authorization header.
+ *
+ * Clients should create one HawkClient object per each server they wish to
+ * interact with.
+ *
+ * @param host
+ *        The url of the host
+ */
+export var HawkClient = function (host) {
+  this.host = host;
+
+  // Clock offset in milliseconds between our client's clock and the date
+  // reported in responses from our host.
+  this._localtimeOffsetMsec = 0;
+};
+
+HawkClient.prototype = {
+  /*
+   * Construct an error message for a response.  Private.
+   *
+   * @param restResponse
+   *        A RESTResponse object from a RESTRequest
+   *
+   * @param error
+   *        A string or object describing the error
+   */
+  _constructError(restResponse, error) {
+    let errorObj = {
+      error,
+      // This object is likely to be JSON.stringify'd, but neither Error()
+      // objects nor Components.Exception objects do the right thing there,
+      // so we add a new element which is simply the .toString() version of
+      // the error object, so it does appear in JSON'd values.
+      errorString: error.toString(),
+      message: restResponse.statusText,
+      code: restResponse.status,
+      errno: restResponse.status,
+      toString() {
+        return this.code + ": " + this.message;
+      },
+    };
+    let retryAfter =
+      restResponse.headers && restResponse.headers["retry-after"];
+    retryAfter = retryAfter ? parseInt(retryAfter) : retryAfter;
+    if (retryAfter) {
+      errorObj.retryAfter = retryAfter;
+      // and notify observers of the retry interval
+      if (this.observerPrefix) {
+        Observers.notify(this.observerPrefix + ":backoff:interval", retryAfter);
+      }
+    }
+    return errorObj;
+  },
+
+  /*
+   *
+   * Update clock offset by determining difference from date gives in the (RFC
+   * 1123) Date header of a server response.  Because HAWK tolerates a window
+   * of one minute of clock skew (so two minutes total since the skew can be
+   * positive or negative), the simple method of calculating offset here is
+   * probably good enough.  We keep the value in milliseconds to make life
+   * easier, even though the value will not have millisecond accuracy.
+   *
+   * @param dateString
+   *        An RFC 1123 date string (e.g., "Mon, 13 Jan 2014 21:45:06 GMT")
+   *
+   * For HAWK clock skew and replay protection, see
+   * https://github.com/hueniverse/hawk#replay-protection
+   */
+  _updateClockOffset(dateString) {
+    try {
+      let serverDateMsec = Date.parse(dateString);
+      this._localtimeOffsetMsec = serverDateMsec - this.now();
+      lazy.log.debug(
+        "Clock offset vs " + this.host + ": " + this._localtimeOffsetMsec
+      );
+    } catch (err) {
+      lazy.log.warn("Bad date header in server response: " + dateString);
+    }
+  },
+
+  /*
+   * Get the current clock offset in milliseconds.
+   *
+   * The offset is the number of milliseconds that must be added to the client
+   * clock to make it equal to the server clock.  For example, if the client is
+   * five minutes ahead of the server, the localtimeOffsetMsec will be -300000.
+   */
+  get localtimeOffsetMsec() {
+    return this._localtimeOffsetMsec;
+  },
+
+  /*
+   * return current time in milliseconds
+   */
+  now() {
+    return Date.now();
+  },
+
+  /* A general method for sending raw RESTRequest calls authorized using HAWK
+   *
+   * @param path
+   *        API endpoint path
+   * @param method
+   *        The HTTP request method
+   * @param credentials
+   *        Hawk credentials
+   * @param payloadObj
+   *        An object that can be encodable as JSON as the payload of the
+   *        request
+   * @param extraHeaders
+   *        An object with header/value pairs to send with the request.
+   * @return Promise
+   *        Returns a promise that resolves to the response of the API call,
+   *        or is rejected with an error.  If the server response can be parsed
+   *        as JSON and contains an 'error' property, the promise will be
+   *        rejected with this JSON-parsed response.
+   */
+  async request(
+    path,
+    method,
+    credentials = null,
+    payloadObj = {},
+    extraHeaders = {},
+    retryOK = true
+  ) {
+    method = method.toLowerCase();
+
+    let uri = this.host + path;
+
+    let extra = {
+      now: this.now(),
+      localtimeOffsetMsec: this.localtimeOffsetMsec,
+      headers: extraHeaders,
+    };
+
+    let request = this.newHAWKAuthenticatedRESTRequest(uri, credentials, extra);
+    let error;
+    let restResponse = await request[method](payloadObj).catch(e => {
+      // Keep a reference to the error, log a message about it, and return the
+      // response anyway.
+      error = e;
+      lazy.log.warn("hawk request error", error);
+      return request.response;
+    });
+
+    // This shouldn't happen anymore, but it's not exactly difficult to handle.
+    if (!restResponse) {
+      throw error;
+    }
+
+    let status = restResponse.status;
+
+    lazy.log.debug(
+      "(Response) " +
+        path +
+        ": code: " +
+        status +
+        " - Status text: " +
+        restResponse.statusText
+    );
+    if (lazy.logPII) {
+      lazy.log.debug("Response text", restResponse.body);
+    }
+
+    // All responses may have backoff headers, which are a server-side safety
+    // valve to allow slowing down clients without hurting performance.
+    this._maybeNotifyBackoff(restResponse, "x-weave-backoff");
+    this._maybeNotifyBackoff(restResponse, "x-backoff");
+
+    if (error) {
+      // When things really blow up, reconstruct an error object that follows
+      // the general format of the server on error responses.
+      throw this._constructError(restResponse, error);
+    }
+
+    this._updateClockOffset(restResponse.headers.date);
+
+    if (status === 401 && retryOK && !("retry-after" in restResponse.headers)) {
+      // Retry once if we were rejected due to a bad timestamp.
+      // Clock offset is adjusted already in the top of this function.
+      lazy.log.debug("Received 401 for " + path + ": retrying");
+      return this.request(
+        path,
+        method,
+        credentials,
+        payloadObj,
+        extraHeaders,
+        false
+      );
+    }
+
+    // If the server returned a json error message, use it in the rejection
+    // of the promise.
+    //
+    // In the case of a 401, in which we are probably being rejected for a
+    // bad timestamp, retry exactly once, during which time clock offset will
+    // be adjusted.
+
+    let jsonResponse = {};
+    try {
+      jsonResponse = JSON.parse(restResponse.body);
+    } catch (notJSON) {}
+
+    let okResponse = 200 <= status && status < 300;
+    if (!okResponse || jsonResponse.error) {
+      if (jsonResponse.error) {
+        throw jsonResponse;
+      }
+      throw this._constructError(restResponse, "Request failed");
+    }
+
+    // It's up to the caller to know how to decode the response.
+    // We just return the whole response.
+    return restResponse;
+  },
+
+  /*
+   * The prefix used for all notifications sent by this module.  This
+   * allows the handler of notifications to be sure they are handling
+   * notifications for the service they expect.
+   *
+   * If not set, no notifications will be sent.
+   */
+  observerPrefix: null,
+
+  // Given an optional header value, notify that a backoff has been requested.
+  _maybeNotifyBackoff(response, headerName) {
+    if (!this.observerPrefix || !response.headers) {
+      return;
+    }
+    let headerVal = response.headers[headerName];
+    if (!headerVal) {
+      return;
+    }
+    let backoffInterval;
+    try {
+      backoffInterval = parseInt(headerVal, 10);
+    } catch (ex) {
+      lazy.log.error(
+        "hawkclient response had invalid backoff value in '" +
+          headerName +
+          "' header: " +
+          headerVal
+      );
+      return;
+    }
+    Observers.notify(
+      this.observerPrefix + ":backoff:interval",
+      backoffInterval
+    );
+  },
+
+  // override points for testing.
+  newHAWKAuthenticatedRESTRequest(uri, credentials, extra) {
+    return new HAWKAuthenticatedRESTRequest(uri, credentials, extra);
+  },
+};
diff --git a/services/common/hawkrequest.sys.mjs b/services/common/hawkrequest.sys.mjs
new file mode 100644
index 0000000000..a856ef032d
--- /dev/null
+++ b/services/common/hawkrequest.sys.mjs
@@ -0,0 +1,197 @@
+/* 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/. */
+
+import { Log } from "resource://gre/modules/Log.sys.mjs";
+
+import { RESTRequest } from "resource://services-common/rest.sys.mjs";
+import { CommonUtils } from "resource://services-common/utils.sys.mjs";
+import { Credentials } from "resource://gre/modules/Credentials.sys.mjs";
+
+const lazy = {};
+
+ChromeUtils.defineESModuleGetters(lazy, {
+  CryptoUtils: "resource://services-crypto/utils.sys.mjs",
+});
+
+/**
+ * Single-use HAWK-authenticated HTTP requests to RESTish resources.
+ *
+ * @param uri
+ *        (String) URI for the RESTRequest constructor
+ *
+ * @param credentials
+ *        (Object) Optional credentials for computing HAWK authentication
+ *        header.
+ *
+ * @param payloadObj
+ *        (Object) Optional object to be converted to JSON payload
+ *
+ * @param extra
+ *        (Object) Optional extra params for HAWK header computation.
+ *        Valid properties are:
+ *
+ *          now:                 <current time in milliseconds>,
+ *          localtimeOffsetMsec: <local clock offset vs server>,
+ *          headers:             <An object with header/value pairs to be sent
+ *                                as headers on the request>
+ *
+ * extra.localtimeOffsetMsec is the value in milliseconds that must be added to
+ * the local clock to make it agree with the server's clock.  For instance, if
+ * the local clock is two minutes ahead of the server, the time offset in
+ * milliseconds will be -120000.
+ */
+
+export var HAWKAuthenticatedRESTRequest = function HawkAuthenticatedRESTRequest(
+  uri,
+  credentials,
+  extra = {}
+) {
+  RESTRequest.call(this, uri);
+
+  this.credentials = credentials;
+  this.now = extra.now || Date.now();
+  this.localtimeOffsetMsec = extra.localtimeOffsetMsec || 0;
+  this._log.trace(
+    "local time, offset: " + this.now + ", " + this.localtimeOffsetMsec
+  );
+  this.extraHeaders = extra.headers || {};
+
+  // Expose for testing
+  this._intl = getIntl();
+};
+
+HAWKAuthenticatedRESTRequest.prototype = {
+  async dispatch(method, data) {
+    let contentType = "text/plain";
+    if (method == "POST" || method == "PUT" || method == "PATCH") {
+      contentType = "application/json";
+    }
+    if (this.credentials) {
+      let options = {
+        now: this.now,
+        localtimeOffsetMsec: this.localtimeOffsetMsec,
+        credentials: this.credentials,
+        payload: (data && JSON.stringify(data)) || "",
+        contentType,
+      };
+      let header = await lazy.CryptoUtils.computeHAWK(
+        this.uri,
+        method,
+        options
+      );
+      this.setHeader("Authorization", header.field);
+    }
+
+    for (let header in this.extraHeaders) {
+      this.setHeader(header, this.extraHeaders[header]);
+    }
+
+    this.setHeader("Content-Type", contentType);
+
+    this.setHeader("Accept-Language", this._intl.accept_languages);
+
+    return super.dispatch(method, data);
+  },
+};
+
+Object.setPrototypeOf(
+  HAWKAuthenticatedRESTRequest.prototype,
+  RESTRequest.prototype
+);
+
+/**
+ * Generic function to derive Hawk credentials.
+ *
+ * Hawk credentials are derived using shared secrets, which depend on the token
+ * in use.
+ *
+ * @param tokenHex
+ *        The current session token encoded in hex
+ * @param context
+ *        A context for the credentials. A protocol version will be prepended
+ *        to the context, see Credentials.keyWord for more information.
+ * @param size
+ *        The size in bytes of the expected derived buffer,
+ *        defaults to 3 * 32.
+ * @return credentials
+ *        Returns an object:
+ *        {
+ *          id: the Hawk id (from the first 32 bytes derived)
+ *          key: the Hawk key (from bytes 32 to 64)
+ *          extra: size - 64 extra bytes (if size > 64)
+ *        }
+ */
+export async function deriveHawkCredentials(tokenHex, context, size = 96) {
+  let token = CommonUtils.hexToBytes(tokenHex);
+  let out = await lazy.CryptoUtils.hkdfLegacy(
+    token,
+    undefined,
+    Credentials.keyWord(context),
+    size
+  );
+
+  let result = {
+    key: out.slice(32, 64),
+    id: CommonUtils.bytesAsHex(out.slice(0, 32)),
+  };
+  if (size > 64) {
+    result.extra = out.slice(64);
+  }
+
+  return result;
+}
+
+// With hawk request, we send the user's accepted-languages with each request.
+// To keep the number of times we read this pref at a minimum, maintain the
+// preference in a stateful object that notices and updates itself when the
+// pref is changed.
+function Intl() {
+  // We won't actually query the pref until the first time we need it
+  this._accepted = "";
+  this._everRead = false;
+  this.init();
+}
+
+Intl.prototype = {
+  init() {
+    Services.prefs.addObserver("intl.accept_languages", this);
+  },
+
+  uninit() {
+    Services.prefs.removeObserver("intl.accept_languages", this);
+  },
+
+  observe(subject, topic, data) {
+    this.readPref();
+  },
+
+  readPref() {
+    this._everRead = true;
+    try {
+      this._accepted = Services.prefs.getComplexValue(
+        "intl.accept_languages",
+        Ci.nsIPrefLocalizedString
+      ).data;
+    } catch (err) {
+      let log = Log.repository.getLogger("Services.Common.RESTRequest");
+      log.error("Error reading intl.accept_languages pref", err);
+    }
+  },
+
+  get accept_languages() {
+    if (!this._everRead) {
+      this.readPref();
+    }
+    return this._accepted;
+  },
+};
+
+// Singleton getter for Intl, creating an instance only when we first need it.
+var intl = null;
+function getIntl() {
+  if (!intl) {
+    intl = new Intl();
+  }
+  return intl;
+}
diff --git a/services/common/kinto-http-client.js b/services/common/kinto-http-client.js
new file mode 100644
index 0000000000..ffd4bd66fc
--- /dev/null
+++ b/services/common/kinto-http-client.js
@@ -0,0 +1,2877 @@
+/*
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+"use strict";
+
+/*
+ * This file is generated from kinto-http.js - do not modify directly.
+ */
+
+const global = this;
+const globalThis = this;
+
+var EXPORTED_SYMBOLS = ["KintoHttpClient"];
+
+const { setTimeout, clearTimeout } = ChromeUtils.importESModule("resource://gre/modules/Timer.sys.mjs");
+const { XPCOMUtils } = ChromeUtils.importESModule("resource://gre/modules/XPCOMUtils.sys.mjs");
+XPCOMUtils.defineLazyGlobalGetters(global, ["fetch"]);
+
+/*
+ * Version 5.3.0 - 284d97d
+ */
+
+(function (global, factory) {
+    typeof exports === 'object' && typeof module !== 'undefined' ? module.exports = factory() :
+    typeof define === 'function' && define.amd ? define(factory) :
+    (global = typeof globalThis !== 'undefined' ? globalThis : global || self, global.KintoHttpClient = factory());
+}(this, (function () { 'use strict';
+
+    /*! *****************************************************************************
+    Copyright (c) Microsoft Corporation.
+
+    Permission to use, copy, modify, and/or distribute this software for any
+    purpose with or without fee is hereby granted.
+
+    THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
+    REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+    AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
+    INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+    LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
+    OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+    PERFORMANCE OF THIS SOFTWARE.
+    ***************************************************************************** */
+    function __decorate(decorators, target, key, desc) {
+        var c = arguments.length, r = c < 3 ? target : desc === null ? desc = Object.getOwnPropertyDescriptor(target, key) : desc, d;
+        if (typeof Reflect === "object" && typeof Reflect.decorate === "function")
+            r = Reflect.decorate(decorators, target, key, desc);
+        else
+            for (var i = decorators.length - 1; i >= 0; i--)
+                if (d = decorators[i])
+                    r = (c < 3 ? d(r) : c > 3 ? d(target, key, r) : d(target, key)) || r;
+        return c > 3 && r && Object.defineProperty(target, key, r), r;
+    }
+
+    /**
+     * Chunks an array into n pieces.
+     *
+     * @private
+     * @param  {Array}  array
+     * @param  {Number} n
+     * @return {Array}
+     */
+    function partition(array, n) {
+        if (n <= 0) {
+            return [array];
+        }
+        return array.reduce((acc, x, i) => {
+            if (i === 0 || i % n === 0) {
+                acc.push([x]);
+            }
+            else {
+                acc[acc.length - 1].push(x);
+            }
+            return acc;
+        }, []);
+    }
+    /**
+     * Returns a Promise always resolving after the specified amount in milliseconds.
+     *
+     * @return Promise<void>
+     */
+    function delay(ms) {
+        return new Promise((resolve) => setTimeout(resolve, ms));
+    }
+    /**
+     * Always returns a resource data object from the provided argument.
+     *
+     * @private
+     * @param  {Object|String} resource
+     * @return {Object}
+     */
+    function toDataBody(resource) {
+        if (isObject(resource)) {
+            return resource;
+        }
+        if (typeof resource === "string") {
+            return { id: resource };
+        }
+        throw new Error("Invalid argument.");
+    }
+    /**
+     * Transforms an object into an URL query string, stripping out any undefined
+     * values.
+     *
+     * @param  {Object} obj
+     * @return {String}
+     */
+    function qsify(obj) {
+        const encode = (v) => encodeURIComponent(typeof v === "boolean" ? String(v) : v);
+        const stripped = cleanUndefinedProperties(obj);
+        return Object.keys(stripped)
+            .map((k) => {
+            const ks = encode(k) + "=";
+            if (Array.isArray(stripped[k])) {
+                return ks + stripped[k].map((v) => encode(v)).join(",");
+            }
+            else {
+                return ks + encode(stripped[k]);
+            }
+        })
+            .join("&");
+    }
+    /**
+     * Checks if a version is within the provided range.
+     *
+     * @param  {String} version    The version to check.
+     * @param  {String} minVersion The minimum supported version (inclusive).
+     * @param  {String} maxVersion The minimum supported version (exclusive).
+     * @throws {Error} If the version is outside of the provided range.
+     */
+    function checkVersion(version, minVersion, maxVersion) {
+        const extract = (str) => str.split(".").map((x) => parseInt(x, 10));
+        const [verMajor, verMinor] = extract(version);
+        const [minMajor, minMinor] = extract(minVersion);
+        const [maxMajor, maxMinor] = extract(maxVersion);
+        const checks = [
+            verMajor < minMajor,
+            verMajor === minMajor && verMinor < minMinor,
+            verMajor > maxMajor,
+            verMajor === maxMajor && verMinor >= maxMinor,
+        ];
+        if (checks.some((x) => x)) {
+            throw new Error(`Version ${version} doesn't satisfy ${minVersion} <= x < ${maxVersion}`);
+        }
+    }
+    /**
+     * Generates a decorator function ensuring a version check is performed against
+     * the provided requirements before executing it.
+     *
+     * @param  {String} min The required min version (inclusive).
+     * @param  {String} max The required max version (inclusive).
+     * @return {Function}
+     */
+    function support(min, max) {
+        return function (
+        // @ts-ignore
+        target, key, descriptor) {
+            const fn = descriptor.value;
+            return {
+                configurable: true,
+                get() {
+                    const wrappedMethod = (...args) => {
+                        // "this" is the current instance which its method is decorated.
+                        const client = this.client ? this.client : this;
+                        return client
+                            .fetchHTTPApiVersion()
+                            .then((version) => checkVersion(version, min, max))
+                            .then(() => fn.apply(this, args));
+                    };
+                    Object.defineProperty(this, key, {
+                        value: wrappedMethod,
+                        configurable: true,
+                        writable: true,
+                    });
+                    return wrappedMethod;
+                },
+            };
+        };
+    }
+    /**
+     * Generates a decorator function ensuring that the specified capabilities are
+     * available on the server before executing it.
+     *
+     * @param  {Array<String>} capabilities The required capabilities.
+     * @return {Function}
+     */
+    function capable(capabilities) {
+        return function (
+        // @ts-ignore
+        target, key, descriptor) {
+            const fn = descriptor.value;
+            return {
+                configurable: true,
+                get() {
+                    const wrappedMethod = (...args) => {
+                        // "this" is the current instance which its method is decorated.
+                        const client = this.client ? this.client : this;
+                        return client
+                            .fetchServerCapabilities()
+                            .then((available) => {
+                            const missing = capabilities.filter((c) => !(c in available));
+                            if (missing.length > 0) {
+                                const missingStr = missing.join(", ");
+                                throw new Error(`Required capabilities ${missingStr} not present on server`);
+                            }
+                        })
+                            .then(() => fn.apply(this, args));
+                    };
+                    Object.defineProperty(this, key, {
+                        value: wrappedMethod,
+                        configurable: true,
+                        writable: true,
+                    });
+                    return wrappedMethod;
+                },
+            };
+        };
+    }
+    /**
+     * Generates a decorator function ensuring an operation is not performed from
+     * within a batch request.
+     *
+     * @param  {String} message The error message to throw.
+     * @return {Function}
+     */
+    function nobatch(message) {
+        return function (
+        // @ts-ignore
+        target, key, descriptor) {
+            const fn = descriptor.value;
+            return {
+                configurable: true,
+                get() {
+                    const wrappedMethod = (...args) => {
+                        // "this" is the current instance which its method is decorated.
+                        if (this._isBatch) {
+                            throw new Error(message);
+                        }
+                        return fn.apply(this, args);
+                    };
+                    Object.defineProperty(this, key, {
+                        value: wrappedMethod,
+                        configurable: true,
+                        writable: true,
+                    });
+                    return wrappedMethod;
+                },
+            };
+        };
+    }
+    /**
+     * Returns true if the specified value is an object (i.e. not an array nor null).
+     * @param  {Object} thing The value to inspect.
+     * @return {bool}
+     */
+    function isObject(thing) {
+        return typeof thing === "object" && thing !== null && !Array.isArray(thing);
+    }
+    /**
+     * Parses a data url.
+     * @param  {String} dataURL The data url.
+     * @return {Object}
+     */
+    function parseDataURL(dataURL) {
+        const regex = /^data:(.*);base64,(.*)/;
+        const match = dataURL.match(regex);
+        if (!match) {
+            throw new Error(`Invalid data-url: ${String(dataURL).substr(0, 32)}...`);
+        }
+        const props = match[1];
+        const base64 = match[2];
+        const [type, ...rawParams] = props.split(";");
+        const params = rawParams.reduce((acc, param) => {
+            const [key, value] = param.split("=");
+            return Object.assign(Object.assign({}, acc), { [key]: value });
+        }, {});
+        return Object.assign(Object.assign({}, params), { type, base64 });
+    }
+    /**
+     * Extracts file information from a data url.
+     * @param  {String} dataURL The data url.
+     * @return {Object}
+     */
+    function extractFileInfo(dataURL) {
+        const { name, type, base64 } = parseDataURL(dataURL);
+        const binary = atob(base64);
+        const array = [];
+        for (let i = 0; i < binary.length; i++) {
+            array.push(binary.charCodeAt(i));
+        }
+        const blob = new Blob([new Uint8Array(array)], { type });
+        return { blob, name };
+    }
+    /**
+     * Creates a FormData instance from a data url and an existing JSON response
+     * body.
+     * @param  {String} dataURL            The data url.
+     * @param  {Object} body               The response body.
+     * @param  {Object} [options={}]       The options object.
+     * @param  {Object} [options.filename] Force attachment file name.
+     * @return {FormData}
+     */
+    function createFormData(dataURL, body, options = {}) {
+        const { filename = "untitled" } = options;
+        const { blob, name } = extractFileInfo(dataURL);
+        const formData = new FormData();
+        formData.append("attachment", blob, name || filename);
+        for (const property in body) {
+            if (typeof body[property] !== "undefined") {
+                formData.append(property, JSON.stringify(body[property]));
+            }
+        }
+        return formData;
+    }
+    /**
+     * Clones an object with all its undefined keys removed.
+     * @private
+     */
+    function cleanUndefinedProperties(obj) {
+        const result = {};
+        for (const key in obj) {
+            if (typeof obj[key] !== "undefined") {
+                result[key] = obj[key];
+            }
+        }
+        return result;
+    }
+    /**
+     * Handle common query parameters for Kinto requests.
+     *
+     * @param  {String}  [path]  The endpoint base path.
+     * @param  {Array}   [options.fields]    Fields to limit the
+     *   request to.
+     * @param  {Object}  [options.query={}]  Additional query arguments.
+     */
+    function addEndpointOptions(path, options = {}) {
+        const query = Object.assign({}, options.query);
+        if (options.fields) {
+            query._fields = options.fields;
+        }
+        const queryString = qsify(query);
+        if (queryString) {
+            return path + "?" + queryString;
+        }
+        return path;
+    }
+    /**
+     * Replace authorization header with an obscured version
+     */
+    function obscureAuthorizationHeader(headers) {
+        const h = new Headers(headers);
+        if (h.has("authorization")) {
+            h.set("authorization", "**** (suppressed)");
+        }
+        const obscuredHeaders = {};
+        for (const [header, value] of h.entries()) {
+            obscuredHeaders[header] = value;
+        }
+        return obscuredHeaders;
+    }
+
+    /**
+     * Kinto server error code descriptors.
+     */
+    const ERROR_CODES = {
+        104: "Missing Authorization Token",
+        105: "Invalid Authorization Token",
+        106: "Request body was not valid JSON",
+        107: "Invalid request parameter",
+        108: "Missing request parameter",
+        109: "Invalid posted data",
+        110: "Invalid Token / id",
+        111: "Missing Token / id",
+        112: "Content-Length header was not provided",
+        113: "Request body too large",
+        114: "Resource was created, updated or deleted meanwhile",
+        115: "Method not allowed on this end point (hint: server may be readonly)",
+        116: "Requested version not available on this server",
+        117: "Client has sent too many requests",
+        121: "Resource access is forbidden for this user",
+        122: "Another resource violates constraint",
+        201: "Service Temporary unavailable due to high load",
+        202: "Service deprecated",
+        999: "Internal Server Error",
+    };
+    class NetworkTimeoutError extends Error {
+        constructor(url, options) {
+            super(`Timeout while trying to access ${url} with ${JSON.stringify(options)}`);
+            if (Error.captureStackTrace) {
+                Error.captureStackTrace(this, NetworkTimeoutError);
+            }
+            this.url = url;
+            this.options = options;
+        }
+    }
+    class UnparseableResponseError extends Error {
+        constructor(response, body, error) {
+            const { status } = response;
+            super(`Response from server unparseable (HTTP ${status || 0}; ${error}): ${body}`);
+            if (Error.captureStackTrace) {
+                Error.captureStackTrace(this, UnparseableResponseError);
+            }
+            this.status = status;
+            this.response = response;
+            this.stack = error.stack;
+            this.error = error;
+        }
+    }
+    /**
+     * "Error" subclass representing a >=400 response from the server.
+     *
+     * Whether or not this is an error depends on your application.
+     *
+     * The `json` field can be undefined if the server responded with an
+     * empty response body. This shouldn't generally happen. Most "bad"
+     * responses come with a JSON error description, or (if they're
+     * fronted by a CDN or nginx or something) occasionally non-JSON
+     * responses (which become UnparseableResponseErrors, above).
+     */
+    class ServerResponse extends Error {
+        constructor(response, json) {
+            const { status } = response;
+            let { statusText } = response;
+            let errnoMsg;
+            if (json) {
+                // Try to fill in information from the JSON error.
+                statusText = json.error || statusText;
+                // Take errnoMsg from either ERROR_CODES or json.message.
+                if (json.errno && json.errno in ERROR_CODES) {
+                    errnoMsg = ERROR_CODES[json.errno];
+                }
+                else if (json.message) {
+                    errnoMsg = json.message;
+                }
+                // If we had both ERROR_CODES and json.message, and they differ,
+                // combine them.
+                if (errnoMsg && json.message && json.message !== errnoMsg) {
+                    errnoMsg += ` (${json.message})`;
+                }
+            }
+            let message = `HTTP ${status} ${statusText}`;
+            if (errnoMsg) {
+                message += `: ${errnoMsg}`;
+            }
+            super(message.trim());
+            if (Error.captureStackTrace) {
+                Error.captureStackTrace(this, ServerResponse);
+            }
+            this.response = response;
+            this.data = json;
+        }
+    }
+
+    var errors = /*#__PURE__*/Object.freeze({
+        __proto__: null,
+        'default': ERROR_CODES,
+        NetworkTimeoutError: NetworkTimeoutError,
+        ServerResponse: ServerResponse,
+        UnparseableResponseError: UnparseableResponseError
+    });
+
+    /**
+     * Enhanced HTTP client for the Kinto protocol.
+     * @private
+     */
+    class HTTP {
+        /**
+         * Constructor.
+         *
+         * @param {EventEmitter} events                       The event handler.
+         * @param {Object}       [options={}}                 The options object.
+         * @param {Number}       [options.timeout=null]       The request timeout in ms, if any (default: `null`).
+         * @param {String}       [options.requestMode="cors"] The HTTP request mode (default: `"cors"`).
+         */
+        constructor(events, options = {}) {
+            // public properties
+            /**
+             * The event emitter instance.
+             * @type {EventEmitter}
+             */
+            this.events = events;
+            /**
+             * The request mode.
+             * @see  https://fetch.spec.whatwg.org/#requestmode
+             * @type {String}
+             */
+            this.requestMode = options.requestMode || HTTP.defaultOptions.requestMode;
+            /**
+             * The request timeout.
+             * @type {Number}
+             */
+            this.timeout = options.timeout || HTTP.defaultOptions.timeout;
+            /**
+             * The fetch() function.
+             * @type {Function}
+             */
+            this.fetchFunc = options.fetchFunc || globalThis.fetch.bind(globalThis);
+        }
+        /**
+         * Default HTTP request headers applied to each outgoing request.
+         *
+         * @type {Object}
+         */
+        static get DEFAULT_REQUEST_HEADERS() {
+            return {
+                Accept: "application/json",
+                "Content-Type": "application/json",
+            };
+        }
+        /**
+         * Default options.
+         *
+         * @type {Object}
+         */
+        static get defaultOptions() {
+            return { timeout: null, requestMode: "cors" };
+        }
+        /**
+         * @private
+         */
+        timedFetch(url, options) {
+            let hasTimedout = false;
+            return new Promise((resolve, reject) => {
+                // Detect if a request has timed out.
+                let _timeoutId;
+                if (this.timeout) {
+                    _timeoutId = setTimeout(() => {
+                        hasTimedout = true;
+                        if (options && options.headers) {
+                            options = Object.assign(Object.assign({}, options), { headers: obscureAuthorizationHeader(options.headers) });
+                        }
+                        reject(new NetworkTimeoutError(url, options));
+                    }, this.timeout);
+                }
+                function proceedWithHandler(fn) {
+                    return (arg) => {
+                        if (!hasTimedout) {
+                            if (_timeoutId) {
+                                clearTimeout(_timeoutId);
+                            }
+                            fn(arg);
+                        }
+                    };
+                }
+                this.fetchFunc(url, options)
+                    .then(proceedWithHandler(resolve))
+                    .catch(proceedWithHandler(reject));
+            });
+        }
+        /**
+         * @private
+         */
+        async processResponse(response) {
+            const { status, headers } = response;
+            const text = await response.text();
+            // Check if we have a body; if so parse it as JSON.
+            let json;
+            if (text.length !== 0) {
+                try {
+                    json = JSON.parse(text);
+                }
+                catch (err) {
+                    throw new UnparseableResponseError(response, text, err);
+                }
+            }
+            if (status >= 400) {
+                throw new ServerResponse(response, json);
+            }
+            return { status, json: json, headers };
+        }
+        /**
+         * @private
+         */
+        async retry(url, retryAfter, request, options) {
+            await delay(retryAfter);
+            return this.request(url, request, Object.assign(Object.assign({}, options), { retry: options.retry - 1 }));
+        }
+        /**
+         * Performs an HTTP request to the Kinto server.
+         *
+         * Resolves with an objet containing the following HTTP response properties:
+         * - `{Number}  status`  The HTTP status code.
+         * - `{Object}  json`    The JSON response body.
+         * - `{Headers} headers` The response headers object; see the ES6 fetch() spec.
+         *
+         * @param  {String} url               The URL.
+         * @param  {Object} [request={}]      The request object, passed to
+         *     fetch() as its options object.
+         * @param  {Object} [request.headers] The request headers object (default: {})
+         * @param  {Object} [options={}]      Options for making the
+         *     request
+         * @param  {Number} [options.retry]   Number of retries (default: 0)
+         * @return {Promise}
+         */
+        async request(url, request = { headers: {} }, options = { retry: 0 }) {
+            // Ensure default request headers are always set
+            request.headers = Object.assign(Object.assign({}, HTTP.DEFAULT_REQUEST_HEADERS), request.headers);
+            // If a multipart body is provided, remove any custom Content-Type header as
+            // the fetch() implementation will add the correct one for us.
+            if (request.body && request.body instanceof FormData) {
+                if (request.headers instanceof Headers) {
+                    request.headers.delete("Content-Type");
+                }
+                else if (!Array.isArray(request.headers)) {
+                    delete request.headers["Content-Type"];
+                }
+            }
+            request.mode = this.requestMode;
+            const response = await this.timedFetch(url, request);
+            const { headers } = response;
+            this._checkForDeprecationHeader(headers);
+            this._checkForBackoffHeader(headers);
+            // Check if the server summons the client to retry after a while.
+            const retryAfter = this._checkForRetryAfterHeader(headers);
+            // If number of allowed of retries is not exhausted, retry the same request.
+            if (retryAfter && options.retry > 0) {
+                return this.retry(url, retryAfter, request, options);
+            }
+            else {
+                return this.processResponse(response);
+            }
+        }
+        _checkForDeprecationHeader(headers) {
+            const alertHeader = headers.get("Alert");
+            if (!alertHeader) {
+                return;
+            }
+            let alert;
+            try {
+                alert = JSON.parse(alertHeader);
+            }
+            catch (err) {
+                console.warn("Unable to parse Alert header message", alertHeader);
+                return;
+            }
+            console.warn(alert.message, alert.url);
+            if (this.events) {
+                this.events.emit("deprecated", alert);
+            }
+        }
+        _checkForBackoffHeader(headers) {
+            let backoffMs;
+            const backoffHeader = headers.get("Backoff");
+            const backoffSeconds = backoffHeader ? parseInt(backoffHeader, 10) : 0;
+            if (backoffSeconds > 0) {
+                backoffMs = new Date().getTime() + backoffSeconds * 1000;
+            }
+            else {
+                backoffMs = 0;
+            }
+            if (this.events) {
+                this.events.emit("backoff", backoffMs);
+            }
+        }
+        _checkForRetryAfterHeader(headers) {
+            const retryAfter = headers.get("Retry-After");
+            if (!retryAfter) {
+                return;
+            }
+            const delay = parseInt(retryAfter, 10) * 1000;
+            const tryAgainAfter = new Date().getTime() + delay;
+            if (this.events) {
+                this.events.emit("retry-after", tryAgainAfter);
+            }
+            return delay;
+        }
+    }
+
+    /**
+     * Endpoints templates.
+     * @type {Object}
+     */
+    const ENDPOINTS = {
+        root: () => "/",
+        batch: () => "/batch",
+        permissions: () => "/permissions",
+        bucket: (bucket) => "/buckets" + (bucket ? `/${bucket}` : ""),
+        history: (bucket) => `${ENDPOINTS.bucket(bucket)}/history`,
+        collection: (bucket, coll) => `${ENDPOINTS.bucket(bucket)}/collections` + (coll ? `/${coll}` : ""),
+        group: (bucket, group) => `${ENDPOINTS.bucket(bucket)}/groups` + (group ? `/${group}` : ""),
+        record: (bucket, coll, id) => `${ENDPOINTS.collection(bucket, coll)}/records` + (id ? `/${id}` : ""),
+        attachment: (bucket, coll, id) => `${ENDPOINTS.record(bucket, coll, id)}/attachment`,
+    };
+
+    const requestDefaults = {
+        safe: false,
+        // check if we should set default content type here
+        headers: {},
+        patch: false,
+    };
+    /**
+     * @private
+     */
+    function safeHeader(safe, last_modified) {
+        if (!safe) {
+            return {};
+        }
+        if (last_modified) {
+            return { "If-Match": `"${last_modified}"` };
+        }
+        return { "If-None-Match": "*" };
+    }
+    /**
+     * @private
+     */
+    function createRequest(path, { data, permissions }, options = {}) {
+        const { headers, safe } = Object.assign(Object.assign({}, requestDefaults), options);
+        const method = options.method || (data && data.id) ? "PUT" : "POST";
+        return {
+            method,
+            path,
+            headers: Object.assign(Object.assign({}, headers), safeHeader(safe)),
+            body: { data, permissions },
+        };
+    }
+    /**
+     * @private
+     */
+    function updateRequest(path, { data, permissions }, options = {}) {
+        const { headers, safe, patch } = Object.assign(Object.assign({}, requestDefaults), options);
+        const { last_modified } = Object.assign(Object.assign({}, data), options);
+        const hasNoData = data &&
+            Object.keys(data).filter((k) => k !== "id" && k !== "last_modified")
+                .length === 0;
+        if (hasNoData) {
+            data = undefined;
+        }
+        return {
+            method: patch ? "PATCH" : "PUT",
+            path,
+            headers: Object.assign(Object.assign({}, headers), safeHeader(safe, last_modified)),
+            body: { data, permissions },
+        };
+    }
+    /**
+     * @private
+     */
+    function jsonPatchPermissionsRequest(path, permissions, opType, options = {}) {
+        const { headers, safe, last_modified } = Object.assign(Object.assign({}, requestDefaults), options);
+        const ops = [];
+        for (const [type, principals] of Object.entries(permissions)) {
+            if (principals) {
+                for (const principal of principals) {
+                    ops.push({
+                        op: opType,
+                        path: `/permissions/${type}/${principal}`,
+                    });
+                }
+            }
+        }
+        return {
+            method: "PATCH",
+            path,
+            headers: Object.assign(Object.assign(Object.assign({}, headers), safeHeader(safe, last_modified)), { "Content-Type": "application/json-patch+json" }),
+            body: ops,
+        };
+    }
+    /**
+     * @private
+     */
+    function deleteRequest(path, options = {}) {
+        const { headers, safe, last_modified } = Object.assign(Object.assign({}, requestDefaults), options);
+        if (safe && !last_modified) {
+            throw new Error("Safe concurrency check requires a last_modified value.");
+        }
+        return {
+            method: "DELETE",
+            path,
+            headers: Object.assign(Object.assign({}, headers), safeHeader(safe, last_modified)),
+        };
+    }
+    /**
+     * @private
+     */
+    function addAttachmentRequest(path, dataURI, { data, permissions } = {}, options = {}) {
+        const { headers, safe, gzipped } = Object.assign(Object.assign({}, requestDefaults), options);
+        const { last_modified } = Object.assign(Object.assign({}, data), options);
+        const body = { data, permissions };
+        const formData = createFormData(dataURI, body, options);
+        const customPath = `${path}${gzipped !== null ? "?gzipped=" + (gzipped ? "true" : "false") : ""}`;
+        return {
+            method: "POST",
+            path: customPath,
+            headers: Object.assign(Object.assign({}, headers), safeHeader(safe, last_modified)),
+            body: formData,
+        };
+    }
+
+    /**
+     * Exports batch responses as a result object.
+     *
+     * @private
+     * @param  {Array} responses The batch subrequest responses.
+     * @param  {Array} requests  The initial issued requests.
+     * @return {Object}
+     */
+    function aggregate(responses = [], requests = []) {
+        if (responses.length !== requests.length) {
+            throw new Error("Responses length should match requests one.");
+        }
+        const results = {
+            errors: [],
+            published: [],
+            conflicts: [],
+            skipped: [],
+        };
+        return responses.reduce((acc, response, index) => {
+            const { status } = response;
+            const request = requests[index];
+            if (status >= 200 && status < 400) {
+                acc.published.push(response.body);
+            }
+            else if (status === 404) {
+                // Extract the id manually from request path while waiting for Kinto/kinto#818
+                const regex = /(buckets|groups|collections|records)\/([^/]+)$/;
+                const extracts = request.path.match(regex);
+                const id = extracts && extracts.length === 3 ? extracts[2] : undefined;
+                acc.skipped.push({
+                    id,
+                    path: request.path,
+                    error: response.body,
+                });
+            }
+            else if (status === 412) {
+                acc.conflicts.push({
+                    // XXX: specifying the type is probably superfluous
+                    type: "outgoing",
+                    local: request.body,
+                    remote: (response.body.details && response.body.details.existing) || null,
+                });
+            }
+            else {
+                acc.errors.push({
+                    path: request.path,
+                    sent: request,
+                    error: response.body,
+                });
+            }
+            return acc;
+        }, results);
+    }
+
+    // Unique ID creation requires a high quality random # generator. In the browser we therefore
+    // require the crypto API and do not support built-in fallback to lower quality random number
+    // generators (like Math.random()).
+    var getRandomValues;
+    var rnds8 = new Uint8Array(16);
+    function rng() {
+        // lazy load so that environments that need to polyfill have a chance to do so
+        if (!getRandomValues) {
+            // getRandomValues needs to be invoked in a context where "this" is a Crypto implementation. Also,
+            // find the complete implementation of crypto (msCrypto) on IE11.
+            getRandomValues = typeof crypto !== 'undefined' && crypto.getRandomValues && crypto.getRandomValues.bind(crypto) || typeof msCrypto !== 'undefined' && typeof msCrypto.getRandomValues === 'function' && msCrypto.getRandomValues.bind(msCrypto);
+            if (!getRandomValues) {
+                throw new Error('crypto.getRandomValues() not supported. See https://github.com/uuidjs/uuid#getrandomvalues-not-supported');
+            }
+        }
+        return getRandomValues(rnds8);
+    }
+
+    var REGEX = /^(?:[0-9a-f]{8}-[0-9a-f]{4}-[1-5][0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}|00000000-0000-0000-0000-000000000000)$/i;
+
+    function validate(uuid) {
+        return typeof uuid === 'string' && REGEX.test(uuid);
+    }
+
+    /**
+     * Convert array of 16 byte values to UUID string format of the form:
+     * XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX
+     */
+    var byteToHex = [];
+    for (var i = 0; i < 256; ++i) {
+        byteToHex.push((i + 0x100).toString(16).substr(1));
+    }
+    function stringify(arr) {
+        var offset = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : 0;
+        // Note: Be careful editing this code!  It's been tuned for performance
+        // and works in ways you may not expect. See https://github.com/uuidjs/uuid/pull/434
+        var uuid = (byteToHex[arr[offset + 0]] + byteToHex[arr[offset + 1]] + byteToHex[arr[offset + 2]] + byteToHex[arr[offset + 3]] + '-' + byteToHex[arr[offset + 4]] + byteToHex[arr[offset + 5]] + '-' + byteToHex[arr[offset + 6]] + byteToHex[arr[offset + 7]] + '-' + byteToHex[arr[offset + 8]] + byteToHex[arr[offset + 9]] + '-' + byteToHex[arr[offset + 10]] + byteToHex[arr[offset + 11]] + byteToHex[arr[offset + 12]] + byteToHex[arr[offset + 13]] + byteToHex[arr[offset + 14]] + byteToHex[arr[offset + 15]]).toLowerCase(); // Consistency check for valid UUID.  If this throws, it's likely due to one
+        // of the following:
+        // - One or more input array values don't map to a hex octet (leading to
+        // "undefined" in the uuid)
+        // - Invalid input values for the RFC `version` or `variant` fields
+        if (!validate(uuid)) {
+            throw TypeError('Stringified UUID is invalid');
+        }
+        return uuid;
+    }
+
+    function v4(options, buf, offset) {
+        options = options || {};
+        var rnds = options.random || (options.rng || rng)(); // Per 4.4, set bits for version and `clock_seq_hi_and_reserved`
+        rnds[6] = rnds[6] & 0x0f | 0x40;
+        rnds[8] = rnds[8] & 0x3f | 0x80; // Copy bytes to buffer, if provided
+        if (buf) {
+            offset = offset || 0;
+            for (var i = 0; i < 16; ++i) {
+                buf[offset + i] = rnds[i];
+            }
+            return buf;
+        }
+        return stringify(rnds);
+    }
+
+    /**
+     * Abstract representation of a selected collection.
+     *
+     */
+    class Collection {
+        /**
+         * Constructor.
+         *
+         * @param  {KintoClient}  client            The client instance.
+         * @param  {Bucket}       bucket            The bucket instance.
+         * @param  {String}       name              The collection name.
+         * @param  {Object}       [options={}]      The options object.
+         * @param  {Object}       [options.headers] The headers object option.
+         * @param  {Boolean}      [options.safe]    The safe option.
+         * @param  {Number}       [options.retry]   The retry option.
+         * @param  {Boolean}      [options.batch]   (Private) Whether this
+         *     Collection is operating as part of a batch.
+         */
+        constructor(client, bucket, name, options = {}) {
+            /**
+             * @ignore
+             */
+            this.client = client;
+            /**
+             * @ignore
+             */
+            this.bucket = bucket;
+            /**
+             * The collection name.
+             * @type {String}
+             */
+            this.name = name;
+            this._endpoints = client.endpoints;
+            /**
+             * @ignore
+             */
+            this._retry = options.retry || 0;
+            this._safe = !!options.safe;
+            // FIXME: This is kind of ugly; shouldn't the bucket be responsible
+            // for doing the merge?
+            this._headers = Object.assign(Object.assign({}, this.bucket.headers), options.headers);
+        }
+        get execute() {
+            return this.client.execute.bind(this.client);
+        }
+        /**
+         * Get the value of "headers" for a given request, merging the
+         * per-request headers with our own "default" headers.
+         *
+         * @private
+         */
+        _getHeaders(options) {
+            return Object.assign(Object.assign({}, this._headers), options.headers);
+        }
+        /**
+         * Get the value of "safe" for a given request, using the
+         * per-request option if present or falling back to our default
+         * otherwise.
+         *
+         * @private
+         * @param {Object} options The options for a request.
+         * @returns {Boolean}
+         */
+        _getSafe(options) {
+            return Object.assign({ safe: this._safe }, options).safe;
+        }
+        /**
+         * As _getSafe, but for "retry".
+         *
+         * @private
+         */
+        _getRetry(options) {
+            return Object.assign({ retry: this._retry }, options).retry;
+        }
+        /**
+         * Retrieves the total number of records in this collection.
+         *
+         * @param  {Object} [options={}]      The options object.
+         * @param  {Object} [options.headers] The headers object option.
+         * @param  {Number} [options.retry=0] Number of retries to make
+         *     when faced with transient errors.
+         * @return {Promise<Number, Error>}
+         */
+        async getTotalRecords(options = {}) {
+            const path = this._endpoints.record(this.bucket.name, this.name);
+            const request = {
+                headers: this._getHeaders(options),
+                path,
+                method: "HEAD",
+            };
+            const { headers } = await this.client.execute(request, {
+                raw: true,
+                retry: this._getRetry(options),
+            });
+            return parseInt(headers.get("Total-Records"), 10);
+        }
+        /**
+         * Retrieves the ETag of the records list, for use with the `since` filtering option.
+         *
+         * @param  {Object} [options={}]      The options object.
+         * @param  {Object} [options.headers] The headers object option.
+         * @param  {Number} [options.retry=0] Number of retries to make
+         *     when faced with transient errors.
+         * @return {Promise<String, Error>}
+         */
+        async getRecordsTimestamp(options = {}) {
+            const path = this._endpoints.record(this.bucket.name, this.name);
+            const request = {
+                headers: this._getHeaders(options),
+                path,
+                method: "HEAD",
+            };
+            const { headers } = (await this.client.execute(request, {
+                raw: true,
+                retry: this._getRetry(options),
+            }));
+            return headers.get("ETag");
+        }
+        /**
+         * Retrieves collection data.
+         *
+         * @param  {Object} [options={}]      The options object.
+         * @param  {Object} [options.headers] The headers object option.
+         * @param  {Object} [options.query]   Query parameters to pass in
+         *     the request. This might be useful for features that aren't
+         *     yet supported by this library.
+         * @param  {Array}  [options.fields]  Limit response to
+         *     just some fields.
+         * @param  {Number} [options.retry=0] Number of retries to make
+         *     when faced with transient errors.
+         * @return {Promise<Object, Error>}
+         */
+        async getData(options = {}) {
+            const path = this._endpoints.collection(this.bucket.name, this.name);
+            const request = { headers: this._getHeaders(options), path };
+            const { data } = (await this.client.execute(request, {
+                retry: this._getRetry(options),
+                query: options.query,
+                fields: options.fields,
+            }));
+            return data;
+        }
+        /**
+         * Set collection data.
+         * @param  {Object}   data                    The collection data object.
+         * @param  {Object}   [options={}]            The options object.
+         * @param  {Object}   [options.headers]       The headers object option.
+         * @param  {Number}   [options.retry=0]       Number of retries to make
+         *     when faced with transient errors.
+         * @param  {Boolean}  [options.safe]          The safe option.
+         * @param  {Boolean}  [options.patch]         The patch option.
+         * @param  {Number}   [options.last_modified] The last_modified option.
+         * @return {Promise<Object, Error>}
+         */
+        async setData(data, options = {}) {
+            if (!isObject(data)) {
+                throw new Error("A collection object is required.");
+            }
+            const { patch, permissions } = options;
+            const { last_modified } = Object.assign(Object.assign({}, data), options);
+            const path = this._endpoints.collection(this.bucket.name, this.name);
+            const request = updateRequest(path, { data, permissions }, {
+                last_modified,
+                patch,
+                headers: this._getHeaders(options),
+                safe: this._getSafe(options),
+            });
+            return this.client.execute(request, {
+                retry: this._getRetry(options),
+            });
+        }
+        /**
+         * Retrieves the list of permissions for this collection.
+         *
+         * @param  {Object} [options={}]      The options object.
+         * @param  {Object} [options.headers] The headers object option.
+         * @param  {Number} [options.retry=0] Number of retries to make
+         *     when faced with transient errors.
+         * @return {Promise<Object, Error>}
+         */
+        async getPermissions(options = {}) {
+            const path = this._endpoints.collection(this.bucket.name, this.name);
+            const request = { headers: this._getHeaders(options), path };
+            const { permissions } = (await this.client.execute(request, {
+                retry: this._getRetry(options),
+            }));
+            return permissions;
+        }
+        /**
+         * Replaces all existing collection permissions with the ones provided.
+         *
+         * @param  {Object}   permissions             The permissions object.
+         * @param  {Object}   [options={}]            The options object
+         * @param  {Object}   [options.headers]       The headers object option.
+         * @param  {Number}   [options.retry=0]       Number of retries to make
+         *     when faced with transient errors.
+         * @param  {Boolean}  [options.safe]          The safe option.
+         * @param  {Number}   [options.last_modified] The last_modified option.
+         * @return {Promise<Object, Error>}
+         */
+        async setPermissions(permissions, options = {}) {
+            if (!isObject(permissions)) {
+                throw new Error("A permissions object is required.");
+            }
+            const path = this._endpoints.collection(this.bucket.name, this.name);
+            const data = { last_modified: options.last_modified };
+            const request = updateRequest(path, { data, permissions }, {
+                headers: this._getHeaders(options),
+                safe: this._getSafe(options),
+            });
+            return this.client.execute(request, {
+                retry: this._getRetry(options),
+            });
+        }
+        /**
+         * Append principals to the collection permissions.
+         *
+         * @param  {Object}  permissions             The permissions object.
+         * @param  {Object}  [options={}]            The options object
+         * @param  {Boolean} [options.safe]          The safe option.
+         * @param  {Object}  [options.headers]       The headers object option.
+         * @param  {Number}  [options.retry=0]       Number of retries to make
+         *     when faced with transient errors.
+         * @param  {Object}  [options.last_modified] The last_modified option.
+         * @return {Promise<Object, Error>}
+         */
+        async addPermissions(permissions, options = {}) {
+            if (!isObject(permissions)) {
+                throw new Error("A permissions object is required.");
+            }
+            const path = this._endpoints.collection(this.bucket.name, this.name);
+            const { last_modified } = options;
+            const request = jsonPatchPermissionsRequest(path, permissions, "add", {
+                last_modified,
+                headers: this._getHeaders(options),
+                safe: this._getSafe(options),
+            });
+            return this.client.execute(request, {
+                retry: this._getRetry(options),
+            });
+        }
+        /**
+         * Remove principals from the collection permissions.
+         *
+         * @param  {Object}  permissions             The permissions object.
+         * @param  {Object}  [options={}]            The options object
+         * @param  {Boolean} [options.safe]          The safe option.
+         * @param  {Object}  [options.headers]       The headers object option.
+         * @param  {Number}  [options.retry=0]       Number of retries to make
+         *     when faced with transient errors.
+         * @param  {Object}  [options.last_modified] The last_modified option.
+         * @return {Promise<Object, Error>}
+         */
+        async removePermissions(permissions, options = {}) {
+            if (!isObject(permissions)) {
+                throw new Error("A permissions object is required.");
+            }
+            const path = this._endpoints.collection(this.bucket.name, this.name);
+            const { last_modified } = options;
+            const request = jsonPatchPermissionsRequest(path, permissions, "remove", {
+                last_modified,
+                headers: this._getHeaders(options),
+                safe: this._getSafe(options),
+            });
+            return this.client.execute(request, {
+                retry: this._getRetry(options),
+            });
+        }
+        /**
+         * Creates a record in current collection.
+         *
+         * @param  {Object}  record                The record to create.
+         * @param  {Object}  [options={}]          The options object.
+         * @param  {Object}  [options.headers]     The headers object option.
+         * @param  {Number}  [options.retry=0]     Number of retries to make
+         *     when faced with transient errors.
+         * @param  {Boolean} [options.safe]        The safe option.
+         * @param  {Object}  [options.permissions] The permissions option.
+         * @return {Promise<Object, Error>}
+         */
+        async createRecord(record, options = {}) {
+            const { permissions } = options;
+            const path = this._endpoints.record(this.bucket.name, this.name, record.id);
+            const request = createRequest(path, { data: record, permissions }, {
+                headers: this._getHeaders(options),
+                safe: this._getSafe(options),
+            });
+            return this.client.execute(request, {
+                retry: this._getRetry(options),
+            });
+        }
+        /**
+         * Adds an attachment to a record, creating the record when it doesn't exist.
+         *
+         * @param  {String}  dataURL                 The data url.
+         * @param  {Object}  [record={}]             The record data.
+         * @param  {Object}  [options={}]            The options object.
+         * @param  {Object}  [options.headers]       The headers object option.
+         * @param  {Number}  [options.retry=0]       Number of retries to make
+         *     when faced with transient errors.
+         * @param  {Boolean} [options.safe]          The safe option.
+         * @param  {Number}  [options.last_modified] The last_modified option.
+         * @param  {Object}  [options.permissions]   The permissions option.
+         * @param  {String}  [options.filename]      Force the attachment filename.
+         * @param  {String}  [options.gzipped]       Force the attachment to be gzipped or not.
+         * @return {Promise<Object, Error>}
+         */
+        async addAttachment(dataURI, record = {}, options = {}) {
+            const { permissions } = options;
+            const id = record.id || v4();
+            const path = this._endpoints.attachment(this.bucket.name, this.name, id);
+            const { last_modified } = Object.assign(Object.assign({}, record), options);
+            const addAttachmentRequest$1 = addAttachmentRequest(path, dataURI, { data: record, permissions }, {
+                last_modified,
+                filename: options.filename,
+                gzipped: options.gzipped,
+                headers: this._getHeaders(options),
+                safe: this._getSafe(options),
+            });
+            await this.client.execute(addAttachmentRequest$1, {
+                stringify: false,
+                retry: this._getRetry(options),
+            });
+            return this.getRecord(id);
+        }
+        /**
+         * Removes an attachment from a given record.
+         *
+         * @param  {Object}  recordId                The record id.
+         * @param  {Object}  [options={}]            The options object.
+         * @param  {Object}  [options.headers]       The headers object option.
+         * @param  {Number}  [options.retry=0]       Number of retries to make
+         *     when faced with transient errors.
+         * @param  {Boolean} [options.safe]          The safe option.
+         * @param  {Number}  [options.last_modified] The last_modified option.
+         */
+        async removeAttachment(recordId, options = {}) {
+            const { last_modified } = options;
+            const path = this._endpoints.attachment(this.bucket.name, this.name, recordId);
+            const request = deleteRequest(path, {
+                last_modified,
+                headers: this._getHeaders(options),
+                safe: this._getSafe(options),
+            });
+            return this.client.execute(request, {
+                retry: this._getRetry(options),
+            });
+        }
+        /**
+         * Updates a record in current collection.
+         *
+         * @param  {Object}  record                  The record to update.
+         * @param  {Object}  [options={}]            The options object.
+         * @param  {Object}  [options.headers]       The headers object option.
+         * @param  {Number}  [options.retry=0]       Number of retries to make
+         *     when faced with transient errors.
+         * @param  {Boolean} [options.safe]          The safe option.
+         * @param  {Number}  [options.last_modified] The last_modified option.
+         * @param  {Object}  [options.permissions]   The permissions option.
+         * @return {Promise<Object, Error>}
+         */
+        async updateRecord(record, options = {}) {
+            if (!isObject(record)) {
+                throw new Error("A record object is required.");
+            }
+            if (!record.id) {
+                throw new Error("A record id is required.");
+            }
+            const { permissions } = options;
+            const { last_modified } = Object.assign(Object.assign({}, record), options);
+            const path = this._endpoints.record(this.bucket.name, this.name, record.id);
+            const request = updateRequest(path, { data: record, permissions }, {
+                headers: this._getHeaders(options),
+                safe: this._getSafe(options),
+                last_modified,
+                patch: !!options.patch,
+            });
+            return this.client.execute(request, {
+                retry: this._getRetry(options),
+            });
+        }
+        /**
+         * Deletes a record from the current collection.
+         *
+         * @param  {Object|String} record                  The record to delete.
+         * @param  {Object}        [options={}]            The options object.
+         * @param  {Object}        [options.headers]       The headers object option.
+         * @param  {Number}        [options.retry=0]       Number of retries to make
+         *     when faced with transient errors.
+         * @param  {Boolean}       [options.safe]          The safe option.
+         * @param  {Number}        [options.last_modified] The last_modified option.
+         * @return {Promise<Object, Error>}
+         */
+        async deleteRecord(record, options = {}) {
+            const recordObj = toDataBody(record);
+            if (!recordObj.id) {
+                throw new Error("A record id is required.");
+            }
+            const { id } = recordObj;
+            const { last_modified } = Object.assign(Object.assign({}, recordObj), options);
+            const path = this._endpoints.record(this.bucket.name, this.name, id);
+            const request = deleteRequest(path, {
+                last_modified,
+                headers: this._getHeaders(options),
+                safe: this._getSafe(options),
+            });
+            return this.client.execute(request, {
+                retry: this._getRetry(options),
+            });
+        }
+        /**
+         * Deletes records from the current collection.
+         *
+         * Sorting is done by passing a `sort` string option:
+         *
+         * - The field to order the results by, prefixed with `-` for descending.
+         * Default: `-last_modified`.
+         *
+         * @see http://kinto.readthedocs.io/en/stable/api/1.x/sorting.html
+         *
+         * Filtering is done by passing a `filters` option object:
+         *
+         * - `{fieldname: "value"}`
+         * - `{min_fieldname: 4000}`
+         * - `{in_fieldname: "1,2,3"}`
+         * - `{not_fieldname: 0}`
+         * - `{exclude_fieldname: "0,1"}`
+         *
+         * @see http://kinto.readthedocs.io/en/stable/api/1.x/filtering.html
+         *
+         * @param  {Object}   [options={}]                    The options object.
+         * @param  {Object}   [options.headers]               The headers object option.
+         * @param  {Number}   [options.retry=0]               Number of retries to make
+         *     when faced with transient errors.
+         * @param  {Object}   [options.filters={}]            The filters object.
+         * @param  {String}   [options.sort="-last_modified"] The sort field.
+         * @param  {String}   [options.at]                    The timestamp to get a snapshot at.
+         * @param  {String}   [options.limit=null]            The limit field.
+         * @param  {String}   [options.pages=1]               The number of result pages to aggregate.
+         * @param  {Number}   [options.since=null]            Only retrieve records modified since the provided timestamp.
+         * @param  {Array}    [options.fields]                Limit response to just some fields.
+         * @return {Promise<Object, Error>}
+         */
+        async deleteRecords(options = {}) {
+            const path = this._endpoints.record(this.bucket.name, this.name);
+            return this.client.paginatedDelete(path, options, {
+                headers: this._getHeaders(options),
+                retry: this._getRetry(options),
+            });
+        }
+        /**
+         * Retrieves a record from the current collection.
+         *
+         * @param  {String} id                The record id to retrieve.
+         * @param  {Object} [options={}]      The options object.
+         * @param  {Object} [options.headers] The headers object option.
+         * @param  {Object} [options.query]   Query parameters to pass in
+         *     the request. This might be useful for features that aren't
+         *     yet supported by this library.
+         * @param  {Array}  [options.fields]  Limit response to
+         *     just some fields.
+         * @param  {Number} [options.retry=0] Number of retries to make
+         *     when faced with transient errors.
+         * @return {Promise<Object, Error>}
+         */
+        async getRecord(id, options = {}) {
+            const path = this._endpoints.record(this.bucket.name, this.name, id);
+            const request = { headers: this._getHeaders(options), path };
+            return this.client.execute(request, {
+                retry: this._getRetry(options),
+                query: options.query,
+                fields: options.fields,
+            });
+        }
+        /**
+         * Lists records from the current collection.
+         *
+         * Sorting is done by passing a `sort` string option:
+         *
+         * - The field to order the results by, prefixed with `-` for descending.
+         * Default: `-last_modified`.
+         *
+         * @see http://kinto.readthedocs.io/en/stable/api/1.x/sorting.html
+         *
+         * Filtering is done by passing a `filters` option object:
+         *
+         * - `{fieldname: "value"}`
+         * - `{min_fieldname: 4000}`
+         * - `{in_fieldname: "1,2,3"}`
+         * - `{not_fieldname: 0}`
+         * - `{exclude_fieldname: "0,1"}`
+         *
+         * @see http://kinto.readthedocs.io/en/stable/api/1.x/filtering.html
+         *
+         * Paginating is done by passing a `limit` option, then calling the `next()`
+         * method from the resolved result object to fetch the next page, if any.
+         *
+         * @param  {Object}   [options={}]                    The options object.
+         * @param  {Object}   [options.headers]               The headers object option.
+         * @param  {Number}   [options.retry=0]               Number of retries to make
+         *     when faced with transient errors.
+         * @param  {Object}   [options.filters={}]            The filters object.
+         * @param  {String}   [options.sort="-last_modified"] The sort field.
+         * @param  {String}   [options.at]                    The timestamp to get a snapshot at.
+         * @param  {String}   [options.limit=null]            The limit field.
+         * @param  {String}   [options.pages=1]               The number of result pages to aggregate.
+         * @param  {Number}   [options.since=null]            Only retrieve records modified since the provided timestamp.
+         * @param  {Array}    [options.fields]                Limit response to just some fields.
+         * @return {Promise<Object, Error>}
+         */
+        async listRecords(options = {}) {
+            const path = this._endpoints.record(this.bucket.name, this.name);
+            if (options.at) {
+                return this.getSnapshot(options.at);
+            }
+            else {
+                return this.client.paginatedList(path, options, {
+                    headers: this._getHeaders(options),
+                    retry: this._getRetry(options),
+                });
+            }
+        }
+        /**
+         * @private
+         */
+        async isHistoryComplete() {
+            // We consider that if we have the collection creation event part of the
+            // history, then all records change events have been tracked.
+            const { data: [oldestHistoryEntry], } = await this.bucket.listHistory({
+                limit: 1,
+                filters: {
+                    action: "create",
+                    resource_name: "collection",
+                    collection_id: this.name,
+                },
+            });
+            return !!oldestHistoryEntry;
+        }
+        /**
+         * @private
+         */
+        async getSnapshot(at) {
+            if (!at || !Number.isInteger(at) || at <= 0) {
+                throw new Error("Invalid argument, expected a positive integer.");
+            }
+            // Retrieve history and check it covers the required time range.
+            // Ensure we have enough history data to retrieve the complete list of
+            // changes.
+            if (!(await this.isHistoryComplete())) {
+                throw new Error("Computing a snapshot is only possible when the full history for a " +
+                    "collection is available. Here, the history plugin seems to have " +
+                    "been enabled after the creation of the collection.");
+            }
+            // Because of https://github.com/Kinto/kinto-http.js/issues/963
+            // we cannot simply rely on the history endpoint.
+            // Our strategy here is to clean-up the history entries from the
+            // records that were deleted via the plural endpoint.
+            // We will detect them by comparing the current state of the collection
+            // and the full history of the collection since its genesis.
+            // List full history of collection.
+            const { data: fullHistory } = await this.bucket.listHistory({
+                pages: Infinity,
+                sort: "last_modified",
+                filters: {
+                    resource_name: "record",
+                    collection_id: this.name,
+                },
+            });
+            // Keep latest entry ever, and latest within snapshot window.
+            // (history is sorted chronologically)
+            const latestEver = new Map();
+            const latestInSnapshot = new Map();
+            for (const entry of fullHistory) {
+                if (entry.target.data.last_modified <= at) {
+                    // Snapshot includes changes right on timestamp.
+                    latestInSnapshot.set(entry.record_id, entry);
+                }
+                latestEver.set(entry.record_id, entry);
+            }
+            // Current records ids in the collection.
+            const { data: current } = await this.listRecords({
+                pages: Infinity,
+                fields: ["id"], // we don't need attributes.
+            });
+            const currentIds = new Set(current.map((record) => record.id));
+            // If a record is not in the current collection, and its
+            // latest history entry isn't a delete then this means that
+            // it was deleted via the plural endpoint (and that we lost track
+            // of this deletion because of bug #963)
+            const deletedViaPlural = new Set();
+            for (const entry of latestEver.values()) {
+                if (entry.action != "delete" && !currentIds.has(entry.record_id)) {
+                    deletedViaPlural.add(entry.record_id);
+                }
+            }
+            // Now reconstruct the collection based on latest version in snapshot
+            // filtering all deleted records.
+            const reconstructed = [];
+            for (const entry of latestInSnapshot.values()) {
+                if (entry.action != "delete" && !deletedViaPlural.has(entry.record_id)) {
+                    reconstructed.push(entry.target.data);
+                }
+            }
+            return {
+                last_modified: String(at),
+                data: Array.from(reconstructed).sort((a, b) => b.last_modified - a.last_modified),
+                next: () => {
+                    throw new Error("Snapshots don't support pagination");
+                },
+                hasNextPage: false,
+                totalRecords: reconstructed.length,
+            };
+        }
+        /**
+         * Performs batch operations at the current collection level.
+         *
+         * @param  {Function} fn                   The batch operation function.
+         * @param  {Object}   [options={}]         The options object.
+         * @param  {Object}   [options.headers]    The headers object option.
+         * @param  {Boolean}  [options.safe]       The safe option.
+         * @param  {Number}   [options.retry]      The retry option.
+         * @param  {Boolean}  [options.aggregate]  Produces a grouped result object.
+         * @return {Promise<Object, Error>}
+         */
+        async batch(fn, options = {}) {
+            return this.client.batch(fn, {
+                bucket: this.bucket.name,
+                collection: this.name,
+                headers: this._getHeaders(options),
+                retry: this._getRetry(options),
+                safe: this._getSafe(options),
+                aggregate: !!options.aggregate,
+            });
+        }
+    }
+    __decorate([
+        capable(["attachments"])
+    ], Collection.prototype, "addAttachment", null);
+    __decorate([
+        capable(["attachments"])
+    ], Collection.prototype, "removeAttachment", null);
+    __decorate([
+        capable(["history"])
+    ], Collection.prototype, "getSnapshot", null);
+
+    /**
+     * Abstract representation of a selected bucket.
+     *
+     */
+    class Bucket {
+        /**
+         * Constructor.
+         *
+         * @param  {KintoClient} client            The client instance.
+         * @param  {String}      name              The bucket name.
+         * @param  {Object}      [options={}]      The headers object option.
+         * @param  {Object}      [options.headers] The headers object option.
+         * @param  {Boolean}     [options.safe]    The safe option.
+         * @param  {Number}      [options.retry]   The retry option.
+         */
+        constructor(client, name, options = {}) {
+            /**
+             * @ignore
+             */
+            this.client = client;
+            /**
+             * The bucket name.
+             * @type {String}
+             */
+            this.name = name;
+            this._endpoints = client.endpoints;
+            /**
+             * @ignore
+             */
+            this._headers = options.headers || {};
+            this._retry = options.retry || 0;
+            this._safe = !!options.safe;
+        }
+        get execute() {
+            return this.client.execute.bind(this.client);
+        }
+        get headers() {
+            return this._headers;
+        }
+        /**
+         * Get the value of "headers" for a given request, merging the
+         * per-request headers with our own "default" headers.
+         *
+         * @private
+         */
+        _getHeaders(options) {
+            return Object.assign(Object.assign({}, this._headers), options.headers);
+        }
+        /**
+         * Get the value of "safe" for a given request, using the
+         * per-request option if present or falling back to our default
+         * otherwise.
+         *
+         * @private
+         * @param {Object} options The options for a request.
+         * @returns {Boolean}
+         */
+        _getSafe(options) {
+            return Object.assign({ safe: this._safe }, options).safe;
+        }
+        /**
+         * As _getSafe, but for "retry".
+         *
+         * @private
+         */
+        _getRetry(options) {
+            return Object.assign({ retry: this._retry }, options).retry;
+        }
+        /**
+         * Selects a collection.
+         *
+         * @param  {String}  name              The collection name.
+         * @param  {Object}  [options={}]      The options object.
+         * @param  {Object}  [options.headers] The headers object option.
+         * @param  {Boolean} [options.safe]    The safe option.
+         * @return {Collection}
+         */
+        collection(name, options = {}) {
+            return new Collection(this.client, this, name, {
+                headers: this._getHeaders(options),
+                retry: this._getRetry(options),
+                safe: this._getSafe(options),
+            });
+        }
+        /**
+         * Retrieves the ETag of the collection list, for use with the `since` filtering option.
+         *
+         * @param  {Object} [options={}]      The options object.
+         * @param  {Object} [options.headers] The headers object option.
+         * @param  {Number} [options.retry=0] Number of retries to make
+         *     when faced with transient errors.
+         * @return {Promise<String, Error>}
+         */
+        async getCollectionsTimestamp(options = {}) {
+            const path = this._endpoints.collection(this.name);
+            const request = {
+                headers: this._getHeaders(options),
+                path,
+                method: "HEAD",
+            };
+            const { headers } = (await this.client.execute(request, {
+                raw: true,
+                retry: this._getRetry(options),
+            }));
+            return headers.get("ETag");
+        }
+        /**
+         * Retrieves the ETag of the group list, for use with the `since` filtering option.
+         *
+         * @param  {Object} [options={}]      The options object.
+         * @param  {Object} [options.headers] The headers object option.
+         * @param  {Number} [options.retry=0] Number of retries to make
+         *     when faced with transient errors.
+         * @return {Promise<String, Error>}
+         */
+        async getGroupsTimestamp(options = {}) {
+            const path = this._endpoints.group(this.name);
+            const request = {
+                headers: this._getHeaders(options),
+                path,
+                method: "HEAD",
+            };
+            const { headers } = (await this.client.execute(request, {
+                raw: true,
+                retry: this._getRetry(options),
+            }));
+            return headers.get("ETag");
+        }
+        /**
+         * Retrieves bucket data.
+         *
+         * @param  {Object} [options={}]      The options object.
+         * @param  {Object} [options.headers] The headers object option.
+         * @param  {Object} [options.query]   Query parameters to pass in
+         *     the request. This might be useful for features that aren't
+         *     yet supported by this library.
+         * @param  {Array}  [options.fields]  Limit response to
+         *     just some fields.
+         * @param  {Number} [options.retry=0] Number of retries to make
+         *     when faced with transient errors.
+         * @return {Promise<Object, Error>}
+         */
+        async getData(options = {}) {
+            const path = this._endpoints.bucket(this.name);
+            const request = {
+                headers: this._getHeaders(options),
+                path,
+            };
+            const { data } = (await this.client.execute(request, {
+                retry: this._getRetry(options),
+                query: options.query,
+                fields: options.fields,
+            }));
+            return data;
+        }
+        /**
+         * Set bucket data.
+         * @param  {Object}  data                    The bucket data object.
+         * @param  {Object}  [options={}]            The options object.
+         * @param  {Object}  [options.headers={}]    The headers object option.
+         * @param  {Boolean} [options.safe]          The safe option.
+         * @param  {Number}  [options.retry=0]       Number of retries to make
+         *     when faced with transient errors.
+         * @param  {Boolean} [options.patch]         The patch option.
+         * @param  {Number}  [options.last_modified] The last_modified option.
+         * @return {Promise<Object, Error>}
+         */
+        async setData(data, options = {}) {
+            if (!isObject(data)) {
+                throw new Error("A bucket object is required.");
+            }
+            const bucket = Object.assign(Object.assign({}, data), { id: this.name });
+            // For default bucket, we need to drop the id from the data object.
+            // Bug in Kinto < 3.1.1
+            const bucketId = bucket.id;
+            if (bucket.id === "default") {
+                delete bucket.id;
+            }
+            const path = this._endpoints.bucket(bucketId);
+            const { patch, permissions } = options;
+            const { last_modified } = Object.assign(Object.assign({}, data), options);
+            const request = updateRequest(path, { data: bucket, permissions }, {
+                last_modified,
+                patch,
+                headers: this._getHeaders(options),
+                safe: this._getSafe(options),
+            });
+            return this.client.execute(request, {
+                retry: this._getRetry(options),
+            });
+        }
+        /**
+         * Retrieves the list of history entries in the current bucket.
+         *
+         * @param  {Object} [options={}]      The options object.
+         * @param  {Object} [options.headers] The headers object option.
+         * @param  {Number} [options.retry=0] Number of retries to make
+         *     when faced with transient errors.
+         * @return {Promise<Array<Object>, Error>}
+         */
+        async listHistory(options = {}) {
+            const path = this._endpoints.history(this.name);
+            return this.client.paginatedList(path, options, {
+                headers: this._getHeaders(options),
+                retry: this._getRetry(options),
+            });
+        }
+        /**
+         * Retrieves the list of collections in the current bucket.
+         *
+         * @param  {Object} [options={}]      The options object.
+         * @param  {Object} [options.filters={}] The filters object.
+         * @param  {Object} [options.headers] The headers object option.
+         * @param  {Number} [options.retry=0] Number of retries to make
+         *     when faced with transient errors.
+         * @param  {Array}  [options.fields]  Limit response to
+         *     just some fields.
+         * @return {Promise<Array<Object>, Error>}
+         */
+        async listCollections(options = {}) {
+            const path = this._endpoints.collection(this.name);
+            return this.client.paginatedList(path, options, {
+                headers: this._getHeaders(options),
+                retry: this._getRetry(options),
+            });
+        }
+        /**
+         * Creates a new collection in current bucket.
+         *
+         * @param  {String|undefined}  id          The collection id.
+         * @param  {Object}  [options={}]          The options object.
+         * @param  {Boolean} [options.safe]        The safe option.
+         * @param  {Object}  [options.headers]     The headers object option.
+         * @param  {Number}  [options.retry=0]     Number of retries to make
+         *     when faced with transient errors.
+         * @param  {Object}  [options.permissions] The permissions object.
+         * @param  {Object}  [options.data]        The data object.
+         * @return {Promise<Object, Error>}
+         */
+        async createCollection(id, options = {}) {
+            const { permissions, data = {} } = options;
+            data.id = id;
+            const path = this._endpoints.collection(this.name, id);
+            const request = createRequest(path, { data, permissions }, {
+                headers: this._getHeaders(options),
+                safe: this._getSafe(options),
+            });
+            return this.client.execute(request, {
+                retry: this._getRetry(options),
+            });
+        }
+        /**
+         * Deletes a collection from the current bucket.
+         *
+         * @param  {Object|String} collection              The collection to delete.
+         * @param  {Object}        [options={}]            The options object.
+         * @param  {Object}        [options.headers]       The headers object option.
+         * @param  {Number}        [options.retry=0]       Number of retries to make
+         *     when faced with transient errors.
+         * @param  {Boolean}       [options.safe]          The safe option.
+         * @param  {Number}        [options.last_modified] The last_modified option.
+         * @return {Promise<Object, Error>}
+         */
+        async deleteCollection(collection, options = {}) {
+            const collectionObj = toDataBody(collection);
+            if (!collectionObj.id) {
+                throw new Error("A collection id is required.");
+            }
+            const { id } = collectionObj;
+            const { last_modified } = Object.assign(Object.assign({}, collectionObj), options);
+            const path = this._endpoints.collection(this.name, id);
+            const request = deleteRequest(path, {
+                last_modified,
+                headers: this._getHeaders(options),
+                safe: this._getSafe(options),
+            });
+            return this.client.execute(request, {
+                retry: this._getRetry(options),
+            });
+        }
+        /**
+         * Deletes collections from the current bucket.
+         *
+         * @param  {Object} [options={}]      The options object.
+         * @param  {Object} [options.filters={}] The filters object.
+         * @param  {Object} [options.headers] The headers object option.
+         * @param  {Number} [options.retry=0] Number of retries to make
+         *     when faced with transient errors.
+         * @param  {Array}  [options.fields]  Limit response to
+         *     just some fields.
+         * @return {Promise<Array<Object>, Error>}
+         */
+        async deleteCollections(options = {}) {
+            const path = this._endpoints.collection(this.name);
+            return this.client.paginatedDelete(path, options, {
+                headers: this._getHeaders(options),
+                retry: this._getRetry(options),
+            });
+        }
+        /**
+         * Retrieves the list of groups in the current bucket.
+         *
+         * @param  {Object} [options={}]      The options object.
+         * @param  {Object} [options.filters={}] The filters object.
+         * @param  {Object} [options.headers] The headers object option.
+         * @param  {Number} [options.retry=0] Number of retries to make
+         *     when faced with transient errors.
+         * @param  {Array}  [options.fields]  Limit response to
+         *     just some fields.
+         * @return {Promise<Array<Object>, Error>}
+         */
+        async listGroups(options = {}) {
+            const path = this._endpoints.group(this.name);
+            return this.client.paginatedList(path, options, {
+                headers: this._getHeaders(options),
+                retry: this._getRetry(options),
+            });
+        }
+        /**
+         * Fetches a group in current bucket.
+         *
+         * @param  {String} id                The group id.
+         * @param  {Object} [options={}]      The options object.
+         * @param  {Object} [options.headers] The headers object option.
+         * @param  {Number} [options.retry=0] Number of retries to make
+         *     when faced with transient errors.
+         * @param  {Object} [options.query]   Query parameters to pass in
+         *     the request. This might be useful for features that aren't
+         *     yet supported by this library.
+         * @param  {Array}  [options.fields]  Limit response to
+         *     just some fields.
+         * @return {Promise<Object, Error>}
+         */
+        async getGroup(id, options = {}) {
+            const path = this._endpoints.group(this.name, id);
+            const request = {
+                headers: this._getHeaders(options),
+                path,
+            };
+            return this.client.execute(request, {
+                retry: this._getRetry(options),
+                query: options.query,
+                fields: options.fields,
+            });
+        }
+        /**
+         * Creates a new group in current bucket.
+         *
+         * @param  {String|undefined}  id                    The group id.
+         * @param  {Array<String>}     [members=[]]          The list of principals.
+         * @param  {Object}            [options={}]          The options object.
+         * @param  {Object}            [options.data]        The data object.
+         * @param  {Object}            [options.permissions] The permissions object.
+         * @param  {Boolean}           [options.safe]        The safe option.
+         * @param  {Object}            [options.headers]     The headers object option.
+         * @param  {Number}            [options.retry=0]     Number of retries to make
+         *     when faced with transient errors.
+         * @return {Promise<Object, Error>}
+         */
+        async createGroup(id, members = [], options = {}) {
+            const data = Object.assign(Object.assign({}, options.data), { id,
+                members });
+            const path = this._endpoints.group(this.name, id);
+            const { permissions } = options;
+            const request = createRequest(path, { data, permissions }, {
+                headers: this._getHeaders(options),
+                safe: this._getSafe(options),
+            });
+            return this.client.execute(request, {
+                retry: this._getRetry(options),
+            });
+        }
+        /**
+         * Updates an existing group in current bucket.
+         *
+         * @param  {Object}  group                   The group object.
+         * @param  {Object}  [options={}]            The options object.
+         * @param  {Object}  [options.data]          The data object.
+         * @param  {Object}  [options.permissions]   The permissions object.
+         * @param  {Boolean} [options.safe]          The safe option.
+         * @param  {Object}  [options.headers]       The headers object option.
+         * @param  {Number}  [options.retry=0]       Number of retries to make
+         *     when faced with transient errors.
+         * @param  {Number}  [options.last_modified] The last_modified option.
+         * @return {Promise<Object, Error>}
+         */
+        async updateGroup(group, options = {}) {
+            if (!isObject(group)) {
+                throw new Error("A group object is required.");
+            }
+            if (!group.id) {
+                throw new Error("A group id is required.");
+            }
+            const data = Object.assign(Object.assign({}, options.data), group);
+            const path = this._endpoints.group(this.name, group.id);
+            const { patch, permissions } = options;
+            const { last_modified } = Object.assign(Object.assign({}, data), options);
+            const request = updateRequest(path, { data, permissions }, {
+                last_modified,
+                patch,
+                headers: this._getHeaders(options),
+                safe: this._getSafe(options),
+            });
+            return this.client.execute(request, {
+                retry: this._getRetry(options),
+            });
+        }
+        /**
+         * Deletes a group from the current bucket.
+         *
+         * @param  {Object|String} group                   The group to delete.
+         * @param  {Object}        [options={}]            The options object.
+         * @param  {Object}        [options.headers]       The headers object option.
+         * @param  {Number}        [options.retry=0]       Number of retries to make
+         *     when faced with transient errors.
+         * @param  {Boolean}       [options.safe]          The safe option.
+         * @param  {Number}        [options.last_modified] The last_modified option.
+         * @return {Promise<Object, Error>}
+         */
+        async deleteGroup(group, options = {}) {
+            const groupObj = toDataBody(group);
+            const { id } = groupObj;
+            const { last_modified } = Object.assign(Object.assign({}, groupObj), options);
+            const path = this._endpoints.group(this.name, id);
+            const request = deleteRequest(path, {
+                last_modified,
+                headers: this._getHeaders(options),
+                safe: this._getSafe(options),
+            });
+            return this.client.execute(request, {
+                retry: this._getRetry(options),
+            });
+        }
+        /**
+         * Deletes groups from the current bucket.
+         *
+         * @param  {Object} [options={}]          The options object.
+         * @param  {Object} [options.filters={}]  The filters object.
+         * @param  {Object} [options.headers]     The headers object option.
+         * @param  {Number} [options.retry=0]     Number of retries to make
+         *     when faced with transient errors.
+         * @param  {Array}  [options.fields]      Limit response to
+         *     just some fields.
+         * @return {Promise<Array<Object>, Error>}
+         */
+        async deleteGroups(options = {}) {
+            const path = this._endpoints.group(this.name);
+            return this.client.paginatedDelete(path, options, {
+                headers: this._getHeaders(options),
+                retry: this._getRetry(options),
+            });
+        }
+        /**
+         * Retrieves the list of permissions for this bucket.
+         *
+         * @param  {Object} [options={}]      The options object.
+         * @param  {Object} [options.headers] The headers object option.
+         * @param  {Number} [options.retry=0] Number of retries to make
+         *     when faced with transient errors.
+         * @return {Promise<Object, Error>}
+         */
+        async getPermissions(options = {}) {
+            const request = {
+                headers: this._getHeaders(options),
+                path: this._endpoints.bucket(this.name),
+            };
+            const { permissions } = (await this.client.execute(request, {
+                retry: this._getRetry(options),
+            }));
+            return permissions;
+        }
+        /**
+         * Replaces all existing bucket permissions with the ones provided.
+         *
+         * @param  {Object}  permissions             The permissions object.
+         * @param  {Object}  [options={}]            The options object
+         * @param  {Boolean} [options.safe]          The safe option.
+         * @param  {Object}  [options.headers={}]    The headers object option.
+         * @param  {Number}  [options.retry=0]       Number of retries to make
+         *     when faced with transient errors.
+         * @param  {Object}  [options.last_modified] The last_modified option.
+         * @return {Promise<Object, Error>}
+         */
+        async setPermissions(permissions, options = {}) {
+            if (!isObject(permissions)) {
+                throw new Error("A permissions object is required.");
+            }
+            const path = this._endpoints.bucket(this.name);
+            const { last_modified } = options;
+            const data = { last_modified };
+            const request = updateRequest(path, { data, permissions }, {
+                headers: this._getHeaders(options),
+                safe: this._getSafe(options),
+            });
+            return this.client.execute(request, {
+                retry: this._getRetry(options),
+            });
+        }
+        /**
+         * Append principals to the bucket permissions.
+         *
+         * @param  {Object}  permissions             The permissions object.
+         * @param  {Object}  [options={}]            The options object
+         * @param  {Boolean} [options.safe]          The safe option.
+         * @param  {Object}  [options.headers]       The headers object option.
+         * @param  {Number}  [options.retry=0]       Number of retries to make
+         *     when faced with transient errors.
+         * @param  {Object}  [options.last_modified] The last_modified option.
+         * @return {Promise<Object, Error>}
+         */
+        async addPermissions(permissions, options = {}) {
+            if (!isObject(permissions)) {
+                throw new Error("A permissions object is required.");
+            }
+            const path = this._endpoints.bucket(this.name);
+            const { last_modified } = options;
+            const request = jsonPatchPermissionsRequest(path, permissions, "add", {
+                last_modified,
+                headers: this._getHeaders(options),
+                safe: this._getSafe(options),
+            });
+            return this.client.execute(request, {
+                retry: this._getRetry(options),
+            });
+        }
+        /**
+         * Remove principals from the bucket permissions.
+         *
+         * @param  {Object}  permissions             The permissions object.
+         * @param  {Object}  [options={}]            The options object
+         * @param  {Boolean} [options.safe]          The safe option.
+         * @param  {Object}  [options.headers]       The headers object option.
+         * @param  {Number}  [options.retry=0]       Number of retries to make
+         *     when faced with transient errors.
+         * @param  {Object}  [options.last_modified] The last_modified option.
+         * @return {Promise<Object, Error>}
+         */
+        async removePermissions(permissions, options = {}) {
+            if (!isObject(permissions)) {
+                throw new Error("A permissions object is required.");
+            }
+            const path = this._endpoints.bucket(this.name);
+            const { last_modified } = options;
+            const request = jsonPatchPermissionsRequest(path, permissions, "remove", {
+                last_modified,
+                headers: this._getHeaders(options),
+                safe: this._getSafe(options),
+            });
+            return this.client.execute(request, {
+                retry: this._getRetry(options),
+            });
+        }
+        /**
+         * Performs batch operations at the current bucket level.
+         *
+         * @param  {Function} fn                   The batch operation function.
+         * @param  {Object}   [options={}]         The options object.
+         * @param  {Object}   [options.headers]    The headers object option.
+         * @param  {Boolean}  [options.safe]       The safe option.
+         * @param  {Number}   [options.retry=0]    The retry option.
+         * @param  {Boolean}  [options.aggregate]  Produces a grouped result object.
+         * @return {Promise<Object, Error>}
+         */
+        async batch(fn, options = {}) {
+            return this.client.batch(fn, {
+                bucket: this.name,
+                headers: this._getHeaders(options),
+                retry: this._getRetry(options),
+                safe: this._getSafe(options),
+                aggregate: !!options.aggregate,
+            });
+        }
+    }
+    __decorate([
+        capable(["history"])
+    ], Bucket.prototype, "listHistory", null);
+
+    /**
+     * Currently supported protocol version.
+     * @type {String}
+     */
+    const SUPPORTED_PROTOCOL_VERSION = "v1";
+    /**
+     * High level HTTP client for the Kinto API.
+     *
+     * @example
+     * const client = new KintoClient("https://kinto.dev.mozaws.net/v1");
+     * client.bucket("default")
+     *    .collection("my-blog")
+     *    .createRecord({title: "First article"})
+     *   .then(console.log.bind(console))
+     *   .catch(console.error.bind(console));
+     */
+    class KintoClientBase {
+        /**
+         * Constructor.
+         *
+         * @param  {String}       remote  The remote URL.
+         * @param  {Object}       [options={}]                  The options object.
+         * @param  {Boolean}      [options.safe=true]           Adds concurrency headers to every requests.
+         * @param  {EventEmitter} [options.events=EventEmitter] The events handler instance.
+         * @param  {Object}       [options.headers={}]          The key-value headers to pass to each request.
+         * @param  {Object}       [options.retry=0]             Number of retries when request fails (default: 0)
+         * @param  {String}       [options.bucket="default"]    The default bucket to use.
+         * @param  {String}       [options.requestMode="cors"]  The HTTP request mode (from ES6 fetch spec).
+         * @param  {Number}       [options.timeout=null]        The request timeout in ms, if any.
+         * @param  {Function}     [options.fetchFunc=fetch]     The function to be used to execute HTTP requests.
+         */
+        constructor(remote, options) {
+            if (typeof remote !== "string" || !remote.length) {
+                throw new Error("Invalid remote URL: " + remote);
+            }
+            if (remote[remote.length - 1] === "/") {
+                remote = remote.slice(0, -1);
+            }
+            this._backoffReleaseTime = null;
+            this._requests = [];
+            this._isBatch = !!options.batch;
+            this._retry = options.retry || 0;
+            this._safe = !!options.safe;
+            this._headers = options.headers || {};
+            // public properties
+            /**
+             * The remote server base URL.
+             * @type {String}
+             */
+            this.remote = remote;
+            /**
+             * Current server information.
+             * @ignore
+             * @type {Object|null}
+             */
+            this.serverInfo = null;
+            /**
+             * The event emitter instance. Should comply with the `EventEmitter`
+             * interface.
+             * @ignore
+             * @type {Class}
+             */
+            this.events = options.events;
+            this.endpoints = ENDPOINTS;
+            const { fetchFunc, requestMode, timeout } = options;
+            /**
+             * The HTTP instance.
+             * @ignore
+             * @type {HTTP}
+             */
+            this.http = new HTTP(this.events, { fetchFunc, requestMode, timeout });
+            this._registerHTTPEvents();
+        }
+        /**
+         * The remote endpoint base URL. Setting the value will also extract and
+         * validate the version.
+         * @type {String}
+         */
+        get remote() {
+            return this._remote;
+        }
+        /**
+         * @ignore
+         */
+        set remote(url) {
+            let version;
+            try {
+                version = url.match(/\/(v\d+)\/?$/)[1];
+            }
+            catch (err) {
+                throw new Error("The remote URL must contain the version: " + url);
+            }
+            if (version !== SUPPORTED_PROTOCOL_VERSION) {
+                throw new Error(`Unsupported protocol version: ${version}`);
+            }
+            this._remote = url;
+            this._version = version;
+        }
+        /**
+         * The current server protocol version, eg. `v1`.
+         * @type {String}
+         */
+        get version() {
+            return this._version;
+        }
+        /**
+         * Backoff remaining time, in milliseconds. Defaults to zero if no backoff is
+         * ongoing.
+         *
+         * @type {Number}
+         */
+        get backoff() {
+            const currentTime = new Date().getTime();
+            if (this._backoffReleaseTime && currentTime < this._backoffReleaseTime) {
+                return this._backoffReleaseTime - currentTime;
+            }
+            return 0;
+        }
+        /**
+         * Registers HTTP events.
+         * @private
+         */
+        _registerHTTPEvents() {
+            // Prevent registering event from a batch client instance
+            if (!this._isBatch && this.events) {
+                this.events.on("backoff", (backoffMs) => {
+                    this._backoffReleaseTime = backoffMs;
+                });
+            }
+        }
+        /**
+         * Retrieve a bucket object to perform operations on it.
+         *
+         * @param  {String}  name              The bucket name.
+         * @param  {Object}  [options={}]      The request options.
+         * @param  {Boolean} [options.safe]    The resulting safe option.
+         * @param  {Number}  [options.retry]   The resulting retry option.
+         * @param  {Object}  [options.headers] The extended headers object option.
+         * @return {Bucket}
+         */
+        bucket(name, options = {}) {
+            return new Bucket(this, name, {
+                headers: this._getHeaders(options),
+                safe: this._getSafe(options),
+                retry: this._getRetry(options),
+            });
+        }
+        /**
+         * Set client "headers" for every request, updating previous headers (if any).
+         *
+         * @param {Object} headers The headers to merge with existing ones.
+         */
+        setHeaders(headers) {
+            this._headers = Object.assign(Object.assign({}, this._headers), headers);
+            this.serverInfo = null;
+        }
+        /**
+         * Get the value of "headers" for a given request, merging the
+         * per-request headers with our own "default" headers.
+         *
+         * Note that unlike other options, headers aren't overridden, but
+         * merged instead.
+         *
+         * @private
+         * @param {Object} options The options for a request.
+         * @returns {Object}
+         */
+        _getHeaders(options) {
+            return Object.assign(Object.assign({}, this._headers), options.headers);
+        }
+        /**
+         * Get the value of "safe" for a given request, using the
+         * per-request option if present or falling back to our default
+         * otherwise.
+         *
+         * @private
+         * @param {Object} options The options for a request.
+         * @returns {Boolean}
+         */
+        _getSafe(options) {
+            return Object.assign({ safe: this._safe }, options).safe;
+        }
+        /**
+         * As _getSafe, but for "retry".
+         *
+         * @private
+         */
+        _getRetry(options) {
+            return Object.assign({ retry: this._retry }, options).retry;
+        }
+        /**
+         * Retrieves the server's "hello" endpoint. This endpoint reveals
+         * server capabilities and settings as well as telling the client
+         * "who they are" according to their given authorization headers.
+         *
+         * @private
+         * @param  {Object}  [options={}] The request options.
+         * @param  {Object}  [options.headers={}] Headers to use when making
+         *     this request.
+         * @param  {Number}  [options.retry=0]    Number of retries to make
+         *     when faced with transient errors.
+         * @return {Promise<Object, Error>}
+         */
+        async _getHello(options = {}) {
+            const path = this.remote + ENDPOINTS.root();
+            const { json } = await this.http.request(path, { headers: this._getHeaders(options) }, { retry: this._getRetry(options) });
+            return json;
+        }
+        /**
+         * Retrieves server information and persist them locally. This operation is
+         * usually performed a single time during the instance lifecycle.
+         *
+         * @param  {Object}  [options={}] The request options.
+         * @param  {Number}  [options.retry=0]    Number of retries to make
+         *     when faced with transient errors.
+         * @return {Promise<Object, Error>}
+         */
+        async fetchServerInfo(options = {}) {
+            if (this.serverInfo) {
+                return this.serverInfo;
+            }
+            this.serverInfo = await this._getHello({ retry: this._getRetry(options) });
+            return this.serverInfo;
+        }
+        /**
+         * Retrieves Kinto server settings.
+         *
+         * @param  {Object}  [options={}] The request options.
+         * @param  {Number}  [options.retry=0]    Number of retries to make
+         *     when faced with transient errors.
+         * @return {Promise<Object, Error>}
+         */
+        async fetchServerSettings(options = {}) {
+            const { settings } = await this.fetchServerInfo(options);
+            return settings;
+        }
+        /**
+         * Retrieve server capabilities information.
+         *
+         * @param  {Object}  [options={}] The request options.
+         * @param  {Number}  [options.retry=0]    Number of retries to make
+         *     when faced with transient errors.
+         * @return {Promise<Object, Error>}
+         */
+        async fetchServerCapabilities(options = {}) {
+            const { capabilities } = await this.fetchServerInfo(options);
+            return capabilities;
+        }
+        /**
+         * Retrieve authenticated user information.
+         *
+         * @param  {Object}  [options={}] The request options.
+         * @param  {Object}  [options.headers={}] Headers to use when making
+         *     this request.
+         * @param  {Number}  [options.retry=0]    Number of retries to make
+         *     when faced with transient errors.
+         * @return {Promise<Object, Error>}
+         */
+        async fetchUser(options = {}) {
+            const { user } = await this._getHello(options);
+            return user;
+        }
+        /**
+         * Retrieve authenticated user information.
+         *
+         * @param  {Object}  [options={}] The request options.
+         * @param  {Number}  [options.retry=0]    Number of retries to make
+         *     when faced with transient errors.
+         * @return {Promise<Object, Error>}
+         */
+        async fetchHTTPApiVersion(options = {}) {
+            const { http_api_version } = await this.fetchServerInfo(options);
+            return http_api_version;
+        }
+        /**
+         * Process batch requests, chunking them according to the batch_max_requests
+         * server setting when needed.
+         *
+         * @param  {Array}  requests     The list of batch subrequests to perform.
+         * @param  {Object} [options={}] The options object.
+         * @return {Promise<Object, Error>}
+         */
+        async _batchRequests(requests, options = {}) {
+            const headers = this._getHeaders(options);
+            if (!requests.length) {
+                return [];
+            }
+            const serverSettings = await this.fetchServerSettings({
+                retry: this._getRetry(options),
+            });
+            const maxRequests = serverSettings["batch_max_requests"];
+            if (maxRequests && requests.length > maxRequests) {
+                const chunks = partition(requests, maxRequests);
+                const results = [];
+                for (const chunk of chunks) {
+                    const result = await this._batchRequests(chunk, options);
+                    results.push(...result);
+                }
+                return results;
+            }
+            const { responses } = (await this.execute({
+                // FIXME: is this really necessary, since it's also present in
+                // the "defaults"?
+                headers,
+                path: ENDPOINTS.batch(),
+                method: "POST",
+                body: {
+                    defaults: { headers },
+                    requests,
+                },
+            }, { retry: this._getRetry(options) }));
+            return responses;
+        }
+        /**
+         * Sends batch requests to the remote server.
+         *
+         * Note: Reserved for internal use only.
+         *
+         * @ignore
+         * @param  {Function} fn                        The function to use for describing batch ops.
+         * @param  {Object}   [options={}]              The options object.
+         * @param  {Boolean}  [options.safe]            The safe option.
+         * @param  {Number}   [options.retry]           The retry option.
+         * @param  {String}   [options.bucket]          The bucket name option.
+         * @param  {String}   [options.collection]      The collection name option.
+         * @param  {Object}   [options.headers]         The headers object option.
+         * @param  {Boolean}  [options.aggregate=false] Produces an aggregated result object.
+         * @return {Promise<Object, Error>}
+         */
+        async batch(fn, options = {}) {
+            const rootBatch = new KintoClientBase(this.remote, {
+                events: this.events,
+                batch: true,
+                safe: this._getSafe(options),
+                retry: this._getRetry(options),
+            });
+            if (options.bucket && options.collection) {
+                fn(rootBatch.bucket(options.bucket).collection(options.collection));
+            }
+            else if (options.bucket) {
+                fn(rootBatch.bucket(options.bucket));
+            }
+            else {
+                fn(rootBatch);
+            }
+            const responses = await this._batchRequests(rootBatch._requests, options);
+            if (options.aggregate) {
+                return aggregate(responses, rootBatch._requests);
+            }
+            else {
+                return responses;
+            }
+        }
+        /**
+         * Executes an atomic HTTP request.
+         *
+         * @param  {Object}  request             The request object.
+         * @param  {String}  request.path        The path to fetch, relative
+         *     to the Kinto server root.
+         * @param  {String}  [request.method="GET"] The method to use in the
+         *     request.
+         * @param  {Body}    [request.body]      The request body.
+         * @param  {Object}  [request.headers={}] The request headers.
+         * @param  {Object}  [options={}]        The options object.
+         * @param  {Boolean} [options.raw=false] If true, resolve with full response
+         * @param  {Boolean} [options.stringify=true] If true, serialize body data to
+         * @param  {Number}  [options.retry=0]   The number of times to
+         *     retry a request if the server responds with Retry-After.
+         * JSON.
+         * @return {Promise<Object, Error>}
+         */
+        async execute(request, options = {}) {
+            const { raw = false, stringify = true } = options;
+            // If we're within a batch, add the request to the stack to send at once.
+            if (this._isBatch) {
+                this._requests.push(request);
+                // Resolve with a message in case people attempt at consuming the result
+                // from within a batch operation.
+                const msg = ("This result is generated from within a batch " +
+                    "operation and should not be consumed.");
+                return raw
+                    ? { status: 0, json: msg, headers: new Headers() }
+                    : msg;
+            }
+            const uri = this.remote + addEndpointOptions(request.path, options);
+            const result = await this.http.request(uri, cleanUndefinedProperties({
+                // Limit requests to only those parts that would be allowed in
+                // a batch request -- don't pass through other fancy fetch()
+                // options like integrity, redirect, mode because they will
+                // break on a batch request.  A batch request only allows
+                // headers, method, path (above), and body.
+                method: request.method,
+                headers: request.headers,
+                body: stringify ? JSON.stringify(request.body) : request.body,
+            }), { retry: this._getRetry(options) });
+            return raw ? result : result.json;
+        }
+        /**
+         * Perform an operation with a given HTTP method on some pages from
+         * a paginated list, following the `next-page` header automatically
+         * until we have processed the requested number of pages. Return a
+         * response with a `.next()` method that can be called to perform
+         * the requested HTTP method on more results.
+         *
+         * @private
+         * @param  {String}  path
+         *     The path to make the request to.
+         * @param  {Object}  params
+         *     The parameters to use when making the request.
+         * @param  {String}  [params.sort="-last_modified"]
+         *     The sorting order to use when doing operation on pages.
+         * @param  {Object}  [params.filters={}]
+         *     The filters to send in the request.
+         * @param  {Number}  [params.limit=undefined]
+         *     The limit to send in the request. Undefined means no limit.
+         * @param  {Number}  [params.pages=undefined]
+         *     The number of pages to operate on. Undefined means one page. Pass
+         *     Infinity to operate on everything.
+         * @param  {String}  [params.since=undefined]
+         *     The ETag from which to start doing operation on pages.
+         * @param  {Array}   [params.fields]
+         *     Limit response to just some fields.
+         * @param  {Object}  [options={}]
+         *     Additional request-level parameters to use in all requests.
+         * @param  {Object}  [options.headers={}]
+         *     Headers to use during all requests.
+         * @param  {Number}  [options.retry=0]
+         *     Number of times to retry each request if the server responds
+         *     with Retry-After.
+         * @param  {String}  [options.method="GET"]
+         *     The method to use in the request.
+         */
+        async paginatedOperation(path, params = {}, options = {}) {
+            // FIXME: this is called even in batch requests, which doesn't
+            // make any sense (since all batch requests get a "dummy"
+            // response; see execute() above).
+            const { sort, filters, limit, pages, since, fields } = Object.assign({ sort: "-last_modified" }, params);
+            // Safety/Consistency check on ETag value.
+            if (since && typeof since !== "string") {
+                throw new Error(`Invalid value for since (${since}), should be ETag value.`);
+            }
+            const query = Object.assign(Object.assign({}, filters), { _sort: sort, _limit: limit, _since: since });
+            if (fields) {
+                query._fields = fields;
+            }
+            const querystring = qsify(query);
+            let results = [], current = 0;
+            const next = async function (nextPage) {
+                if (!nextPage) {
+                    throw new Error("Pagination exhausted.");
+                }
+                return processNextPage(nextPage);
+            };
+            const processNextPage = async (nextPage) => {
+                const { headers } = options;
+                return handleResponse(await this.http.request(nextPage, { headers }));
+            };
+            const pageResults = (results, nextPage, etag) => {
+                // ETag string is supposed to be opaque and stored «as-is».
+                // ETag header values are quoted (because of * and W/"foo").
+                return {
+                    last_modified: etag ? etag.replace(/"/g, "") : etag,
+                    data: results,
+                    next: next.bind(null, nextPage),
+                    hasNextPage: !!nextPage,
+                    totalRecords: -1,
+                };
+            };
+            const handleResponse = async function ({ headers = new Headers(), json = {}, }) {
+                const nextPage = headers.get("Next-Page");
+                const etag = headers.get("ETag");
+                if (!pages) {
+                    return pageResults(json.data, nextPage, etag);
+                }
+                // Aggregate new results with previous ones
+                results = results.concat(json.data);
+                current += 1;
+                if (current >= pages || !nextPage) {
+                    // Pagination exhausted
+                    return pageResults(results, nextPage, etag);
+                }
+                // Follow next page
+                return processNextPage(nextPage);
+            };
+            return handleResponse((await this.execute(
+            // N.B.: This doesn't use _getHeaders, because all calls to
+            // `paginatedList` are assumed to come from calls that already
+            // have headers merged at e.g. the bucket or collection level.
+            {
+                headers: options.headers ? options.headers : {},
+                path: path + "?" + querystring,
+                method: options.method,
+            }, 
+            // N.B. This doesn't use _getRetry, because all calls to
+            // `paginatedList` are assumed to come from calls that already
+            // used `_getRetry` at e.g. the bucket or collection level.
+            { raw: true, retry: options.retry || 0 })));
+        }
+        /**
+         * Fetch some pages from a paginated list, following the `next-page`
+         * header automatically until we have fetched the requested number
+         * of pages. Return a response with a `.next()` method that can be
+         * called to fetch more results.
+         *
+         * @private
+         * @param  {String}  path
+         *     The path to make the request to.
+         * @param  {Object}  params
+         *     The parameters to use when making the request.
+         * @param  {String}  [params.sort="-last_modified"]
+         *     The sorting order to use when fetching.
+         * @param  {Object}  [params.filters={}]
+         *     The filters to send in the request.
+         * @param  {Number}  [params.limit=undefined]
+         *     The limit to send in the request. Undefined means no limit.
+         * @param  {Number}  [params.pages=undefined]
+         *     The number of pages to fetch. Undefined means one page. Pass
+         *     Infinity to fetch everything.
+         * @param  {String}  [params.since=undefined]
+         *     The ETag from which to start fetching.
+         * @param  {Array}   [params.fields]
+         *     Limit response to just some fields.
+         * @param  {Object}  [options={}]
+         *     Additional request-level parameters to use in all requests.
+         * @param  {Object}  [options.headers={}]
+         *     Headers to use during all requests.
+         * @param  {Number}  [options.retry=0]
+         *     Number of times to retry each request if the server responds
+         *     with Retry-After.
+         */
+        async paginatedList(path, params = {}, options = {}) {
+            return this.paginatedOperation(path, params, options);
+        }
+        /**
+         * Delete multiple objects, following the pagination if the number of
+         * objects exceeds the page limit until we have deleted the requested
+         * number of pages. Return a response with a `.next()` method that can
+         * be called to delete more results.
+         *
+         * @private
+         * @param  {String}  path
+         *     The path to make the request to.
+         * @param  {Object}  params
+         *     The parameters to use when making the request.
+         * @param  {String}  [params.sort="-last_modified"]
+         *     The sorting order to use when deleting.
+         * @param  {Object}  [params.filters={}]
+         *     The filters to send in the request.
+         * @param  {Number}  [params.limit=undefined]
+         *     The limit to send in the request. Undefined means no limit.
+         * @param  {Number}  [params.pages=undefined]
+         *     The number of pages to delete. Undefined means one page. Pass
+         *     Infinity to delete everything.
+         * @param  {String}  [params.since=undefined]
+         *     The ETag from which to start deleting.
+         * @param  {Array}   [params.fields]
+         *     Limit response to just some fields.
+         * @param  {Object}  [options={}]
+         *     Additional request-level parameters to use in all requests.
+         * @param  {Object}  [options.headers={}]
+         *     Headers to use during all requests.
+         * @param  {Number}  [options.retry=0]
+         *     Number of times to retry each request if the server responds
+         *     with Retry-After.
+         */
+        paginatedDelete(path, params = {}, options = {}) {
+            const { headers, safe, last_modified } = options;
+            const deleteRequest$1 = deleteRequest(path, {
+                headers,
+                safe: safe ? safe : false,
+                last_modified,
+            });
+            return this.paginatedOperation(path, params, Object.assign(Object.assign({}, options), { headers: deleteRequest$1.headers, method: "DELETE" }));
+        }
+        /**
+         * Lists all permissions.
+         *
+         * @param  {Object} [options={}]      The options object.
+         * @param  {Object} [options.headers={}] Headers to use when making
+         *     this request.
+         * @param  {Number} [options.retry=0]    Number of retries to make
+         *     when faced with transient errors.
+         * @return {Promise<Object[], Error>}
+         */
+        async listPermissions(options = {}) {
+            const path = ENDPOINTS.permissions();
+            // Ensure the default sort parameter is something that exists in permissions
+            // entries, as `last_modified` doesn't; here, we pick "id".
+            const paginationOptions = Object.assign({ sort: "id" }, options);
+            return this.paginatedList(path, paginationOptions, {
+                headers: this._getHeaders(options),
+                retry: this._getRetry(options),
+            });
+        }
+        /**
+         * Retrieves the list of buckets.
+         *
+         * @param  {Object} [options={}]      The options object.
+         * @param  {Object} [options.headers={}] Headers to use when making
+         *     this request.
+         * @param  {Number} [options.retry=0]    Number of retries to make
+         *     when faced with transient errors.
+         * @param  {Object} [options.filters={}] The filters object.
+         * @param  {Array}  [options.fields]     Limit response to
+         *     just some fields.
+         * @return {Promise<Object[], Error>}
+         */
+        async listBuckets(options = {}) {
+            const path = ENDPOINTS.bucket();
+            return this.paginatedList(path, options, {
+                headers: this._getHeaders(options),
+                retry: this._getRetry(options),
+            });
+        }
+        /**
+         * Creates a new bucket on the server.
+         *
+         * @param  {String|null}  id                The bucket name (optional).
+         * @param  {Object}       [options={}]      The options object.
+         * @param  {Boolean}      [options.data]    The bucket data option.
+         * @param  {Boolean}      [options.safe]    The safe option.
+         * @param  {Object}       [options.headers] The headers object option.
+         * @param  {Number}       [options.retry=0] Number of retries to make
+         *     when faced with transient errors.
+         * @return {Promise<Object, Error>}
+         */
+        async createBucket(id, options = {}) {
+            const { data, permissions } = options;
+            const _data = Object.assign(Object.assign({}, data), { id: id ? id : undefined });
+            const path = _data.id ? ENDPOINTS.bucket(_data.id) : ENDPOINTS.bucket();
+            return this.execute(createRequest(path, { data: _data, permissions }, {
+                headers: this._getHeaders(options),
+                safe: this._getSafe(options),
+            }), { retry: this._getRetry(options) });
+        }
+        /**
+         * Deletes a bucket from the server.
+         *
+         * @ignore
+         * @param  {Object|String} bucket                  The bucket to delete.
+         * @param  {Object}        [options={}]            The options object.
+         * @param  {Boolean}       [options.safe]          The safe option.
+         * @param  {Object}        [options.headers]       The headers object option.
+         * @param  {Number}        [options.retry=0]       Number of retries to make
+         *     when faced with transient errors.
+         * @param  {Number}        [options.last_modified] The last_modified option.
+         * @return {Promise<Object, Error>}
+         */
+        async deleteBucket(bucket, options = {}) {
+            const bucketObj = toDataBody(bucket);
+            if (!bucketObj.id) {
+                throw new Error("A bucket id is required.");
+            }
+            const path = ENDPOINTS.bucket(bucketObj.id);
+            const { last_modified } = Object.assign(Object.assign({}, bucketObj), options);
+            return this.execute(deleteRequest(path, {
+                last_modified,
+                headers: this._getHeaders(options),
+                safe: this._getSafe(options),
+            }), { retry: this._getRetry(options) });
+        }
+        /**
+         * Deletes buckets.
+         *
+         * @param  {Object} [options={}]             The options object.
+         * @param  {Boolean} [options.safe]          The safe option.
+         * @param  {Object} [options.headers={}]     Headers to use when making
+         *     this request.
+         * @param  {Number} [options.retry=0]        Number of retries to make
+         *     when faced with transient errors.
+         * @param  {Object} [options.filters={}]     The filters object.
+         * @param  {Array}  [options.fields]         Limit response to
+         *     just some fields.
+         * @param  {Number}  [options.last_modified] The last_modified option.
+         * @return {Promise<Object[], Error>}
+         */
+        async deleteBuckets(options = {}) {
+            const path = ENDPOINTS.bucket();
+            return this.paginatedDelete(path, options, {
+                headers: this._getHeaders(options),
+                retry: this._getRetry(options),
+                safe: options.safe,
+                last_modified: options.last_modified,
+            });
+        }
+        async createAccount(username, password) {
+            return this.execute(createRequest(`/accounts/${username}`, { data: { password } }, { method: "PUT" }));
+        }
+    }
+    __decorate([
+        nobatch("This operation is not supported within a batch operation.")
+    ], KintoClientBase.prototype, "fetchServerSettings", null);
+    __decorate([
+        nobatch("This operation is not supported within a batch operation.")
+    ], KintoClientBase.prototype, "fetchServerCapabilities", null);
+    __decorate([
+        nobatch("This operation is not supported within a batch operation.")
+    ], KintoClientBase.prototype, "fetchUser", null);
+    __decorate([
+        nobatch("This operation is not supported within a batch operation.")
+    ], KintoClientBase.prototype, "fetchHTTPApiVersion", null);
+    __decorate([
+        nobatch("Can't use batch within a batch!")
+    ], KintoClientBase.prototype, "batch", null);
+    __decorate([
+        capable(["permissions_endpoint"])
+    ], KintoClientBase.prototype, "listPermissions", null);
+    __decorate([
+        support("1.4", "2.0")
+    ], KintoClientBase.prototype, "deleteBuckets", null);
+    __decorate([
+        capable(["accounts"])
+    ], KintoClientBase.prototype, "createAccount", null);
+
+    /*
+     *
+     * Licensed under the Apache License, Version 2.0 (the "License");
+     * you may not use this file except in compliance with the License.
+     * You may obtain a copy of the License at
+     *
+     *     http://www.apache.org/licenses/LICENSE-2.0
+     *
+     * Unless required by applicable law or agreed to in writing, software
+     * distributed under the License is distributed on an "AS IS" BASIS,
+     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+     * See the License for the specific language governing permissions and
+     * limitations under the License.
+     */
+    const { EventEmitter } = ChromeUtils.importESModule("resource://gre/modules/EventEmitter.sys.mjs");
+    class KintoHttpClient extends KintoClientBase {
+        constructor(remote, options = {}) {
+            const events = {};
+            EventEmitter.decorate(events);
+            super(remote, Object.assign({ events: events }, options));
+        }
+    }
+    KintoHttpClient.errors = errors;
+
+    return KintoHttpClient;
+
+})));
diff --git a/services/common/kinto-offline-client.js b/services/common/kinto-offline-client.js
new file mode 100644
index 0000000000..9996e89854
--- /dev/null
+++ b/services/common/kinto-offline-client.js
@@ -0,0 +1,2643 @@
+/*
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+"use strict";
+
+/*
+ * This file is generated from kinto.js - do not modify directly.
+ */
+
+// This is required because with Babel compiles ES2015 modules into a
+// require() form that tries to keep its modules on "this", but
+// doesn't specify "this", leaving it to default to the global
+// object. However, in strict mode, "this" no longer defaults to the
+// global object, so expose the global object explicitly. Babel's
+// compiled output will use a variable called "global" if one is
+// present.
+//
+// See https://bugzilla.mozilla.org/show_bug.cgi?id=1394556#c3 for
+// more details.
+const global = this;
+
+var EXPORTED_SYMBOLS = ["Kinto"];
+
+/*
+ * Version 13.0.0 - 7fbf95d
+ */
+
+(function (global, factory) {
+  typeof exports === 'object' && typeof module !== 'undefined' ? module.exports = factory() :
+  typeof define === 'function' && define.amd ? define(factory) :
+  (global = global || self, global.Kinto = factory());
+}(this, (function () { 'use strict';
+
+  /**
+   * Base db adapter.
+   *
+   * @abstract
+   */
+  class BaseAdapter {
+      /**
+       * Deletes every records present in the database.
+       *
+       * @abstract
+       * @return {Promise}
+       */
+      clear() {
+          throw new Error("Not Implemented.");
+      }
+      /**
+       * Executes a batch of operations within a single transaction.
+       *
+       * @abstract
+       * @param  {Function} callback The operation callback.
+       * @param  {Object}   options  The options object.
+       * @return {Promise}
+       */
+      execute(callback, options = { preload: [] }) {
+          throw new Error("Not Implemented.");
+      }
+      /**
+       * Retrieve a record by its primary key from the database.
+       *
+       * @abstract
+       * @param  {String} id The record id.
+       * @return {Promise}
+       */
+      get(id) {
+          throw new Error("Not Implemented.");
+      }
+      /**
+       * Lists all records from the database.
+       *
+       * @abstract
+       * @param  {Object} params  The filters and order to apply to the results.
+       * @return {Promise}
+       */
+      list(params = { filters: {}, order: "" }) {
+          throw new Error("Not Implemented.");
+      }
+      /**
+       * Store the lastModified value.
+       *
+       * @abstract
+       * @param  {Number}  lastModified
+       * @return {Promise}
+       */
+      saveLastModified(lastModified) {
+          throw new Error("Not Implemented.");
+      }
+      /**
+       * Retrieve saved lastModified value.
+       *
+       * @abstract
+       * @return {Promise}
+       */
+      getLastModified() {
+          throw new Error("Not Implemented.");
+      }
+      /**
+       * Load records in bulk that were exported from a server.
+       *
+       * @abstract
+       * @param  {Array} records The records to load.
+       * @return {Promise}
+       */
+      importBulk(records) {
+          throw new Error("Not Implemented.");
+      }
+      /**
+       * Load a dump of records exported from a server.
+       *
+       * @deprecated Use {@link importBulk} instead.
+       * @abstract
+       * @param  {Array} records The records to load.
+       * @return {Promise}
+       */
+      loadDump(records) {
+          throw new Error("Not Implemented.");
+      }
+      saveMetadata(metadata) {
+          throw new Error("Not Implemented.");
+      }
+      getMetadata() {
+          throw new Error("Not Implemented.");
+      }
+  }
+
+  const RE_RECORD_ID = /^[a-zA-Z0-9][a-zA-Z0-9_-]*$/;
+  /**
+   * Checks if a value is undefined.
+   * @param  {Any}  value
+   * @return {Boolean}
+   */
+  function _isUndefined(value) {
+      return typeof value === "undefined";
+  }
+  /**
+   * Sorts records in a list according to a given ordering.
+   *
+   * @param  {String} order The ordering, eg. `-last_modified`.
+   * @param  {Array}  list  The collection to order.
+   * @return {Array}
+   */
+  function sortObjects(order, list) {
+      const hasDash = order[0] === "-";
+      const field = hasDash ? order.slice(1) : order;
+      const direction = hasDash ? -1 : 1;
+      return list.slice().sort((a, b) => {
+          if (a[field] && _isUndefined(b[field])) {
+              return direction;
+          }
+          if (b[field] && _isUndefined(a[field])) {
+              return -direction;
+          }
+          if (_isUndefined(a[field]) && _isUndefined(b[field])) {
+              return 0;
+          }
+          return a[field] > b[field] ? direction : -direction;
+      });
+  }
+  /**
+   * Test if a single object matches all given filters.
+   *
+   * @param  {Object} filters  The filters object.
+   * @param  {Object} entry    The object to filter.
+   * @return {Boolean}
+   */
+  function filterObject(filters, entry) {
+      return Object.keys(filters).every(filter => {
+          const value = filters[filter];
+          if (Array.isArray(value)) {
+              return value.some(candidate => candidate === entry[filter]);
+          }
+          else if (typeof value === "object") {
+              return filterObject(value, entry[filter]);
+          }
+          else if (!Object.prototype.hasOwnProperty.call(entry, filter)) {
+              console.error(`The property ${filter} does not exist`);
+              return false;
+          }
+          return entry[filter] === value;
+      });
+  }
+  /**
+   * Resolves a list of functions sequentially, which can be sync or async; in
+   * case of async, functions must return a promise.
+   *
+   * @param  {Array} fns  The list of functions.
+   * @param  {Any}   init The initial value.
+   * @return {Promise}
+   */
+  function waterfall(fns, init) {
+      if (!fns.length) {
+          return Promise.resolve(init);
+      }
+      return fns.reduce((promise, nextFn) => {
+          return promise.then(nextFn);
+      }, Promise.resolve(init));
+  }
+  /**
+   * Simple deep object comparison function. This only supports comparison of
+   * serializable JavaScript objects.
+   *
+   * @param  {Object} a The source object.
+   * @param  {Object} b The compared object.
+   * @return {Boolean}
+   */
+  function deepEqual(a, b) {
+      if (a === b) {
+          return true;
+      }
+      if (typeof a !== typeof b) {
+          return false;
+      }
+      if (!(a && typeof a == "object") || !(b && typeof b == "object")) {
+          return false;
+      }
+      if (Object.keys(a).length !== Object.keys(b).length) {
+          return false;
+      }
+      for (const k in a) {
+          if (!deepEqual(a[k], b[k])) {
+              return false;
+          }
+      }
+      return true;
+  }
+  /**
+   * Return an object without the specified keys.
+   *
+   * @param  {Object} obj        The original object.
+   * @param  {Array}  keys       The list of keys to exclude.
+   * @return {Object}            A copy without the specified keys.
+   */
+  function omitKeys(obj, keys = []) {
+      const result = Object.assign({}, obj);
+      for (const key of keys) {
+          delete result[key];
+      }
+      return result;
+  }
+  function arrayEqual(a, b) {
+      if (a.length !== b.length) {
+          return false;
+      }
+      for (let i = a.length; i--;) {
+          if (a[i] !== b[i]) {
+              return false;
+          }
+      }
+      return true;
+  }
+  function makeNestedObjectFromArr(arr, val, nestedFiltersObj) {
+      const last = arr.length - 1;
+      return arr.reduce((acc, cv, i) => {
+          if (i === last) {
+              return (acc[cv] = val);
+          }
+          else if (Object.prototype.hasOwnProperty.call(acc, cv)) {
+              return acc[cv];
+          }
+          else {
+              return (acc[cv] = {});
+          }
+      }, nestedFiltersObj);
+  }
+  function transformSubObjectFilters(filtersObj) {
+      const transformedFilters = {};
+      for (const key in filtersObj) {
+          const keysArr = key.split(".");
+          const val = filtersObj[key];
+          makeNestedObjectFromArr(keysArr, val, transformedFilters);
+      }
+      return transformedFilters;
+  }
+
+  const INDEXED_FIELDS = ["id", "_status", "last_modified"];
+  /**
+   * Small helper that wraps the opening of an IndexedDB into a Promise.
+   *
+   * @param dbname          {String}   The database name.
+   * @param version         {Integer}  Schema version
+   * @param onupgradeneeded {Function} The callback to execute if schema is
+   *                                   missing or different.
+   * @return {Promise<IDBDatabase>}
+   */
+  async function open(dbname, { version, onupgradeneeded }) {
+      return new Promise((resolve, reject) => {
+          const request = indexedDB.open(dbname, version);
+          request.onupgradeneeded = event => {
+              const db = event.target.result;
+              db.onerror = event => reject(event.target.error);
+              // When an upgrade is needed, a transaction is started.
+              const transaction = event.target.transaction;
+              transaction.onabort = event => {
+                  const error = event.target.error ||
+                      transaction.error ||
+                      new DOMException("The operation has been aborted", "AbortError");
+                  reject(error);
+              };
+              // Callback for store creation etc.
+              return onupgradeneeded(event);
+          };
+          request.onerror = event => {
+              reject(event.target.error);
+          };
+          request.onsuccess = event => {
+              const db = event.target.result;
+              resolve(db);
+          };
+      });
+  }
+  /**
+   * Helper to run the specified callback in a single transaction on the
+   * specified store.
+   * The helper focuses on transaction wrapping into a promise.
+   *
+   * @param db           {IDBDatabase} The database instance.
+   * @param name         {String}      The store name.
+   * @param callback     {Function}    The piece of code to execute in the transaction.
+   * @param options      {Object}      Options.
+   * @param options.mode {String}      Transaction mode (default: read).
+   * @return {Promise} any value returned by the callback.
+   */
+  async function execute(db, name, callback, options = {}) {
+      const { mode } = options;
+      return new Promise((resolve, reject) => {
+          // On Safari, calling IDBDatabase.transaction with mode == undefined raises
+          // a TypeError.
+          const transaction = mode
+              ? db.transaction([name], mode)
+              : db.transaction([name]);
+          const store = transaction.objectStore(name);
+          // Let the callback abort this transaction.
+          const abort = e => {
+              transaction.abort();
+              reject(e);
+          };
+          // Execute the specified callback **synchronously**.
+          let result;
+          try {
+              result = callback(store, abort);
+          }
+          catch (e) {
+              abort(e);
+          }
+          transaction.onerror = event => reject(event.target.error);
+          transaction.oncomplete = event => resolve(result);
+          transaction.onabort = event => {
+              const error = event.target.error ||
+                  transaction.error ||
+                  new DOMException("The operation has been aborted", "AbortError");
+              reject(error);
+          };
+      });
+  }
+  /**
+   * Helper to wrap the deletion of an IndexedDB database into a promise.
+   *
+   * @param dbName {String} the database to delete
+   * @return {Promise}
+   */
+  async function deleteDatabase(dbName) {
+      return new Promise((resolve, reject) => {
+          const request = indexedDB.deleteDatabase(dbName);
+          request.onsuccess = event => resolve(event.target);
+          request.onerror = event => reject(event.target.error);
+      });
+  }
+  /**
+   * IDB cursor handlers.
+   * @type {Object}
+   */
+  const cursorHandlers = {
+      all(filters, done) {
+          const results = [];
+          return event => {
+              const cursor = event.target.result;
+              if (cursor) {
+                  const { value } = cursor;
+                  if (filterObject(filters, value)) {
+                      results.push(value);
+                  }
+                  cursor.continue();
+              }
+              else {
+                  done(results);
+              }
+          };
+      },
+      in(values, filters, done) {
+          const results = [];
+          let i = 0;
+          return function (event) {
+              const cursor = event.target.result;
+              if (!cursor) {
+                  done(results);
+                  return;
+              }
+              const { key, value } = cursor;
+              // `key` can be an array of two values (see `keyPath` in indices definitions).
+              // `values` can be an array of arrays if we filter using an index whose key path
+              // is an array (eg. `cursorHandlers.in([["bid/cid", 42], ["bid/cid", 43]], ...)`)
+              while (key > values[i]) {
+                  // The cursor has passed beyond this key. Check next.
+                  ++i;
+                  if (i === values.length) {
+                      done(results); // There is no next. Stop searching.
+                      return;
+                  }
+              }
+              const isEqual = Array.isArray(key)
+                  ? arrayEqual(key, values[i])
+                  : key === values[i];
+              if (isEqual) {
+                  if (filterObject(filters, value)) {
+                      results.push(value);
+                  }
+                  cursor.continue();
+              }
+              else {
+                  cursor.continue(values[i]);
+              }
+          };
+      },
+  };
+  /**
+   * Creates an IDB request and attach it the appropriate cursor event handler to
+   * perform a list query.
+   *
+   * Multiple matching values are handled by passing an array.
+   *
+   * @param  {String}           cid        The collection id (ie. `{bid}/{cid}`)
+   * @param  {IDBStore}         store      The IDB store.
+   * @param  {Object}           filters    Filter the records by field.
+   * @param  {Function}         done       The operation completion handler.
+   * @return {IDBRequest}
+   */
+  function createListRequest(cid, store, filters, done) {
+      const filterFields = Object.keys(filters);
+      // If no filters, get all results in one bulk.
+      if (filterFields.length == 0) {
+          const request = store.index("cid").getAll(IDBKeyRange.only(cid));
+          request.onsuccess = event => done(event.target.result);
+          return request;
+      }
+      // Introspect filters and check if they leverage an indexed field.
+      const indexField = filterFields.find(field => {
+          return INDEXED_FIELDS.includes(field);
+      });
+      if (!indexField) {
+          // Iterate on all records for this collection (ie. cid)
+          const isSubQuery = Object.keys(filters).some(key => key.includes(".")); // (ie. filters: {"article.title": "hello"})
+          if (isSubQuery) {
+              const newFilter = transformSubObjectFilters(filters);
+              const request = store.index("cid").openCursor(IDBKeyRange.only(cid));
+              request.onsuccess = cursorHandlers.all(newFilter, done);
+              return request;
+          }
+          const request = store.index("cid").openCursor(IDBKeyRange.only(cid));
+          request.onsuccess = cursorHandlers.all(filters, done);
+          return request;
+      }
+      // If `indexField` was used already, don't filter again.
+      const remainingFilters = omitKeys(filters, [indexField]);
+      // value specified in the filter (eg. `filters: { _status: ["created", "updated"] }`)
+      const value = filters[indexField];
+      // For the "id" field, use the primary key.
+      const indexStore = indexField == "id" ? store : store.index(indexField);
+      // WHERE IN equivalent clause
+      if (Array.isArray(value)) {
+          if (value.length === 0) {
+              return done([]);
+          }
+          const values = value.map(i => [cid, i]).sort();
+          const range = IDBKeyRange.bound(values[0], values[values.length - 1]);
+          const request = indexStore.openCursor(range);
+          request.onsuccess = cursorHandlers.in(values, remainingFilters, done);
+          return request;
+      }
+      // If no filters on custom attribute, get all results in one bulk.
+      if (remainingFilters.length == 0) {
+          const request = indexStore.getAll(IDBKeyRange.only([cid, value]));
+          request.onsuccess = event => done(event.target.result);
+          return request;
+      }
+      // WHERE field = value clause
+      const request = indexStore.openCursor(IDBKeyRange.only([cid, value]));
+      request.onsuccess = cursorHandlers.all(remainingFilters, done);
+      return request;
+  }
+  class IDBError extends Error {
+      constructor(method, err) {
+          super(`IndexedDB ${method}() ${err.message}`);
+          this.name = err.name;
+          this.stack = err.stack;
+      }
+  }
+  /**
+   * IndexedDB adapter.
+   *
+   * This adapter doesn't support any options.
+   */
+  class IDB extends BaseAdapter {
+      /* Expose the IDBError class publicly */
+      static get IDBError() {
+          return IDBError;
+      }
+      /**
+       * Constructor.
+       *
+       * @param  {String} cid  The key base for this collection (eg. `bid/cid`)
+       * @param  {Object} options
+       * @param  {String} options.dbName         The IndexedDB name (default: `"KintoDB"`)
+       * @param  {String} options.migrateOldData Whether old database data should be migrated (default: `false`)
+       */
+      constructor(cid, options = {}) {
+          super();
+          this.cid = cid;
+          this.dbName = options.dbName || "KintoDB";
+          this._options = options;
+          this._db = null;
+      }
+      _handleError(method, err) {
+          throw new IDBError(method, err);
+      }
+      /**
+       * Ensures a connection to the IndexedDB database has been opened.
+       *
+       * @override
+       * @return {Promise}
+       */
+      async open() {
+          if (this._db) {
+              return this;
+          }
+          // In previous versions, we used to have a database with name `${bid}/${cid}`.
+          // Check if it exists, and migrate data once new schema is in place.
+          // Note: the built-in migrations from IndexedDB can only be used if the
+          // database name does not change.
+          const dataToMigrate = this._options.migrateOldData
+              ? await migrationRequired(this.cid)
+              : null;
+          this._db = await open(this.dbName, {
+              version: 2,
+              onupgradeneeded: event => {
+                  const db = event.target.result;
+                  if (event.oldVersion < 1) {
+                      // Records store
+                      const recordsStore = db.createObjectStore("records", {
+                          keyPath: ["_cid", "id"],
+                      });
+                      // An index to obtain all the records in a collection.
+                      recordsStore.createIndex("cid", "_cid");
+                      // Here we create indices for every known field in records by collection.
+                      // Local record status ("synced", "created", "updated", "deleted")
+                      recordsStore.createIndex("_status", ["_cid", "_status"]);
+                      // Last modified field
+                      recordsStore.createIndex("last_modified", ["_cid", "last_modified"]);
+                      // Timestamps store
+                      db.createObjectStore("timestamps", {
+                          keyPath: "cid",
+                      });
+                  }
+                  if (event.oldVersion < 2) {
+                      // Collections store
+                      db.createObjectStore("collections", {
+                          keyPath: "cid",
+                      });
+                  }
+              },
+          });
+          if (dataToMigrate) {
+              const { records, timestamp } = dataToMigrate;
+              await this.importBulk(records);
+              await this.saveLastModified(timestamp);
+              console.log(`${this.cid}: data was migrated successfully.`);
+              // Delete the old database.
+              await deleteDatabase(this.cid);
+              console.warn(`${this.cid}: old database was deleted.`);
+          }
+          return this;
+      }
+      /**
+       * Closes current connection to the database.
+       *
+       * @override
+       * @return {Promise}
+       */
+      close() {
+          if (this._db) {
+              this._db.close(); // indexedDB.close is synchronous
+              this._db = null;
+          }
+          return Promise.resolve();
+      }
+      /**
+       * Returns a transaction and an object store for a store name.
+       *
+       * To determine if a transaction has completed successfully, we should rather
+       * listen to the transaction’s complete event rather than the IDBObjectStore
+       * request’s success event, because the transaction may still fail after the
+       * success event fires.
+       *
+       * @param  {String}      name  Store name
+       * @param  {Function}    callback to execute
+       * @param  {Object}      options Options
+       * @param  {String}      options.mode  Transaction mode ("readwrite" or undefined)
+       * @return {Object}
+       */
+      async prepare(name, callback, options) {
+          await this.open();
+          await execute(this._db, name, callback, options);
+      }
+      /**
+       * Deletes every records in the current collection.
+       *
+       * @override
+       * @return {Promise}
+       */
+      async clear() {
+          try {
+              await this.prepare("records", store => {
+                  const range = IDBKeyRange.only(this.cid);
+                  const request = store.index("cid").openKeyCursor(range);
+                  request.onsuccess = event => {
+                      const cursor = event.target.result;
+                      if (cursor) {
+                          store.delete(cursor.primaryKey);
+                          cursor.continue();
+                      }
+                  };
+                  return request;
+              }, { mode: "readwrite" });
+          }
+          catch (e) {
+              this._handleError("clear", e);
+          }
+      }
+      /**
+       * Executes the set of synchronous CRUD operations described in the provided
+       * callback within an IndexedDB transaction, for current db store.
+       *
+       * The callback will be provided an object exposing the following synchronous
+       * CRUD operation methods: get, create, update, delete.
+       *
+       * Important note: because limitations in IndexedDB implementations, no
+       * asynchronous code should be performed within the provided callback; the
+       * promise will therefore be rejected if the callback returns a Promise.
+       *
+       * Options:
+       * - {Array} preload: The list of record IDs to fetch and make available to
+       *   the transaction object get() method (default: [])
+       *
+       * @example
+       * const db = new IDB("example");
+       * const result = await db.execute(transaction => {
+       *   transaction.create({id: 1, title: "foo"});
+       *   transaction.update({id: 2, title: "bar"});
+       *   transaction.delete(3);
+       *   return "foo";
+       * });
+       *
+       * @override
+       * @param  {Function} callback The operation description callback.
+       * @param  {Object}   options  The options object.
+       * @return {Promise}
+       */
+      async execute(callback, options = { preload: [] }) {
+          // Transactions in IndexedDB are autocommited when a callback does not
+          // perform any additional operation.
+          // The way Promises are implemented in Firefox (see https://bugzilla.mozilla.org/show_bug.cgi?id=1193394)
+          // prevents using within an opened transaction.
+          // To avoid managing asynchronocity in the specified `callback`, we preload
+          // a list of record in order to execute the `callback` synchronously.
+          // See also:
+          // - http://stackoverflow.com/a/28388805/330911
+          // - http://stackoverflow.com/a/10405196
+          // - https://jakearchibald.com/2015/tasks-microtasks-queues-and-schedules/
+          let result;
+          await this.prepare("records", (store, abort) => {
+              const runCallback = (preloaded = []) => {
+                  // Expose a consistent API for every adapter instead of raw store methods.
+                  const proxy = transactionProxy(this, store, preloaded);
+                  // The callback is executed synchronously within the same transaction.
+                  try {
+                      const returned = callback(proxy);
+                      if (returned instanceof Promise) {
+                          // XXX: investigate how to provide documentation details in error.
+                          throw new Error("execute() callback should not return a Promise.");
+                      }
+                      // Bring to scope that will be returned (once promise awaited).
+                      result = returned;
+                  }
+                  catch (e) {
+                      // The callback has thrown an error explicitly. Abort transaction cleanly.
+                      abort(e);
+                  }
+              };
+              // No option to preload records, go straight to `callback`.
+              if (!options.preload.length) {
+                  return runCallback();
+              }
+              // Preload specified records using a list request.
+              const filters = { id: options.preload };
+              createListRequest(this.cid, store, filters, records => {
+                  // Store obtained records by id.
+                  const preloaded = {};
+                  for (const record of records) {
+                      delete record["_cid"];
+                      preloaded[record.id] = record;
+                  }
+                  runCallback(preloaded);
+              });
+          }, { mode: "readwrite" });
+          return result;
+      }
+      /**
+       * Retrieve a record by its primary key from the IndexedDB database.
+       *
+       * @override
+       * @param  {String} id The record id.
+       * @return {Promise}
+       */
+      async get(id) {
+          try {
+              let record;
+              await this.prepare("records", store => {
+                  store.get([this.cid, id]).onsuccess = e => (record = e.target.result);
+              });
+              return record;
+          }
+          catch (e) {
+              this._handleError("get", e);
+          }
+      }
+      /**
+       * Lists all records from the IndexedDB database.
+       *
+       * @override
+       * @param  {Object} params  The filters and order to apply to the results.
+       * @return {Promise}
+       */
+      async list(params = { filters: {} }) {
+          const { filters } = params;
+          try {
+              let results = [];
+              await this.prepare("records", store => {
+                  createListRequest(this.cid, store, filters, _results => {
+                      // we have received all requested records that match the filters,
+                      // we now park them within current scope and hide the `_cid` attribute.
+                      for (const result of _results) {
+                          delete result["_cid"];
+                      }
+                      results = _results;
+                  });
+              });
+              // The resulting list of records is sorted.
+              // XXX: with some efforts, this could be fully implemented using IDB API.
+              return params.order ? sortObjects(params.order, results) : results;
+          }
+          catch (e) {
+              this._handleError("list", e);
+          }
+      }
+      /**
+       * Store the lastModified value into metadata store.
+       *
+       * @override
+       * @param  {Number}  lastModified
+       * @return {Promise}
+       */
+      async saveLastModified(lastModified) {
+          const value = parseInt(lastModified, 10) || null;
+          try {
+              await this.prepare("timestamps", store => {
+                  if (value === null) {
+                      store.delete(this.cid);
+                  }
+                  else {
+                      store.put({ cid: this.cid, value });
+                  }
+              }, { mode: "readwrite" });
+              return value;
+          }
+          catch (e) {
+              this._handleError("saveLastModified", e);
+          }
+      }
+      /**
+       * Retrieve saved lastModified value.
+       *
+       * @override
+       * @return {Promise}
+       */
+      async getLastModified() {
+          try {
+              let entry = null;
+              await this.prepare("timestamps", store => {
+                  store.get(this.cid).onsuccess = e => (entry = e.target.result);
+              });
+              return entry ? entry.value : null;
+          }
+          catch (e) {
+              this._handleError("getLastModified", e);
+          }
+      }
+      /**
+       * Load a dump of records exported from a server.
+       *
+       * @deprecated Use {@link importBulk} instead.
+       * @abstract
+       * @param  {Array} records The records to load.
+       * @return {Promise}
+       */
+      async loadDump(records) {
+          return this.importBulk(records);
+      }
+      /**
+       * Load records in bulk that were exported from a server.
+       *
+       * @abstract
+       * @param  {Array} records The records to load.
+       * @return {Promise}
+       */
+      async importBulk(records) {
+          try {
+              await this.execute(transaction => {
+                  // Since the put operations are asynchronous, we chain
+                  // them together. The last one will be waited for the
+                  // `transaction.oncomplete` callback. (see #execute())
+                  let i = 0;
+                  putNext();
+                  function putNext() {
+                      if (i == records.length) {
+                          return;
+                      }
+                      // On error, `transaction.onerror` is called.
+                      transaction.update(records[i]).onsuccess = putNext;
+                      ++i;
+                  }
+              });
+              const previousLastModified = await this.getLastModified();
+              const lastModified = Math.max(...records.map(record => record.last_modified));
+              if (lastModified > previousLastModified) {
+                  await this.saveLastModified(lastModified);
+              }
+              return records;
+          }
+          catch (e) {
+              this._handleError("importBulk", e);
+          }
+      }
+      async saveMetadata(metadata) {
+          try {
+              await this.prepare("collections", store => store.put({ cid: this.cid, metadata }), { mode: "readwrite" });
+              return metadata;
+          }
+          catch (e) {
+              this._handleError("saveMetadata", e);
+          }
+      }
+      async getMetadata() {
+          try {
+              let entry = null;
+              await this.prepare("collections", store => {
+                  store.get(this.cid).onsuccess = e => (entry = e.target.result);
+              });
+              return entry ? entry.metadata : null;
+          }
+          catch (e) {
+              this._handleError("getMetadata", e);
+          }
+      }
+  }
+  /**
+   * IDB transaction proxy.
+   *
+   * @param  {IDB} adapter        The call IDB adapter
+   * @param  {IDBStore} store     The IndexedDB database store.
+   * @param  {Array}    preloaded The list of records to make available to
+   *                              get() (default: []).
+   * @return {Object}
+   */
+  function transactionProxy(adapter, store, preloaded = []) {
+      const _cid = adapter.cid;
+      return {
+          create(record) {
+              store.add(Object.assign(Object.assign({}, record), { _cid }));
+          },
+          update(record) {
+              return store.put(Object.assign(Object.assign({}, record), { _cid }));
+          },
+          delete(id) {
+              store.delete([_cid, id]);
+          },
+          get(id) {
+              return preloaded[id];
+          },
+      };
+  }
+  /**
+   * Up to version 10.X of kinto.js, each collection had its own collection.
+   * The database name was `${bid}/${cid}` (eg. `"blocklists/certificates"`)
+   * and contained only one store with the same name.
+   */
+  async function migrationRequired(dbName) {
+      let exists = true;
+      const db = await open(dbName, {
+          version: 1,
+          onupgradeneeded: event => {
+              exists = false;
+          },
+      });
+      // Check that the DB we're looking at is really a legacy one,
+      // and not some remainder of the open() operation above.
+      exists &=
+          db.objectStoreNames.contains("__meta__") &&
+              db.objectStoreNames.contains(dbName);
+      if (!exists) {
+          db.close();
+          // Testing the existence creates it, so delete it :)
+          await deleteDatabase(dbName);
+          return null;
+      }
+      console.warn(`${dbName}: old IndexedDB database found.`);
+      try {
+          // Scan all records.
+          let records;
+          await execute(db, dbName, store => {
+              store.openCursor().onsuccess = cursorHandlers.all({}, res => (records = res));
+          });
+          console.log(`${dbName}: found ${records.length} records.`);
+          // Check if there's a entry for this.
+          let timestamp = null;
+          await execute(db, "__meta__", store => {
+              store.get(`${dbName}-lastModified`).onsuccess = e => {
+                  timestamp = e.target.result ? e.target.result.value : null;
+              };
+          });
+          // Some previous versions, also used to store the timestamps without prefix.
+          if (!timestamp) {
+              await execute(db, "__meta__", store => {
+                  store.get("lastModified").onsuccess = e => {
+                      timestamp = e.target.result ? e.target.result.value : null;
+                  };
+              });
+          }
+          console.log(`${dbName}: ${timestamp ? "found" : "no"} timestamp.`);
+          // Those will be inserted in the new database/schema.
+          return { records, timestamp };
+      }
+      catch (e) {
+          console.error("Error occured during migration", e);
+          return null;
+      }
+      finally {
+          db.close();
+      }
+  }
+
+  var uuid4 = {};
+
+  const RECORD_FIELDS_TO_CLEAN = ["_status"];
+  const AVAILABLE_HOOKS = ["incoming-changes"];
+  const IMPORT_CHUNK_SIZE = 200;
+  /**
+   * Compare two records omitting local fields and synchronization
+   * attributes (like _status and last_modified)
+   * @param {Object} a    A record to compare.
+   * @param {Object} b    A record to compare.
+   * @param {Array} localFields Additional fields to ignore during the comparison
+   * @return {boolean}
+   */
+  function recordsEqual(a, b, localFields = []) {
+      const fieldsToClean = RECORD_FIELDS_TO_CLEAN.concat(["last_modified"]).concat(localFields);
+      const cleanLocal = r => omitKeys(r, fieldsToClean);
+      return deepEqual(cleanLocal(a), cleanLocal(b));
+  }
+  /**
+   * Synchronization result object.
+   */
+  class SyncResultObject {
+      /**
+       * Public constructor.
+       */
+      constructor() {
+          /**
+           * Current synchronization result status; becomes `false` when conflicts or
+           * errors are registered.
+           * @type {Boolean}
+           */
+          this.lastModified = null;
+          this._lists = {};
+          [
+              "errors",
+              "created",
+              "updated",
+              "deleted",
+              "published",
+              "conflicts",
+              "skipped",
+              "resolved",
+              "void",
+          ].forEach(l => (this._lists[l] = []));
+          this._cached = {};
+      }
+      /**
+       * Adds entries for a given result type.
+       *
+       * @param {String} type    The result type.
+       * @param {Array}  entries The result entries.
+       * @return {SyncResultObject}
+       */
+      add(type, entries) {
+          if (!Array.isArray(this._lists[type])) {
+              console.warn(`Unknown type "${type}"`);
+              return;
+          }
+          if (!Array.isArray(entries)) {
+              entries = [entries];
+          }
+          this._lists[type] = this._lists[type].concat(entries);
+          delete this._cached[type];
+          return this;
+      }
+      get ok() {
+          return this.errors.length + this.conflicts.length === 0;
+      }
+      get errors() {
+          return this._lists["errors"];
+      }
+      get conflicts() {
+          return this._lists["conflicts"];
+      }
+      get skipped() {
+          return this._deduplicate("skipped");
+      }
+      get resolved() {
+          return this._deduplicate("resolved");
+      }
+      get created() {
+          return this._deduplicate("created");
+      }
+      get updated() {
+          return this._deduplicate("updated");
+      }
+      get deleted() {
+          return this._deduplicate("deleted");
+      }
+      get published() {
+          return this._deduplicate("published");
+      }
+      _deduplicate(list) {
+          if (!(list in this._cached)) {
+              // Deduplicate entries by id. If the values don't have `id` attribute, just
+              // keep all.
+              const recordsWithoutId = new Set();
+              const recordsById = new Map();
+              this._lists[list].forEach(record => {
+                  if (!record.id) {
+                      recordsWithoutId.add(record);
+                  }
+                  else {
+                      recordsById.set(record.id, record);
+                  }
+              });
+              this._cached[list] = Array.from(recordsById.values()).concat(Array.from(recordsWithoutId));
+          }
+          return this._cached[list];
+      }
+      /**
+       * Reinitializes result entries for a given result type.
+       *
+       * @param  {String} type The result type.
+       * @return {SyncResultObject}
+       */
+      reset(type) {
+          this._lists[type] = [];
+          delete this._cached[type];
+          return this;
+      }
+      toObject() {
+          // Only used in tests.
+          return {
+              ok: this.ok,
+              lastModified: this.lastModified,
+              errors: this.errors,
+              created: this.created,
+              updated: this.updated,
+              deleted: this.deleted,
+              skipped: this.skipped,
+              published: this.published,
+              conflicts: this.conflicts,
+              resolved: this.resolved,
+          };
+      }
+  }
+  class ServerWasFlushedError extends Error {
+      constructor(clientTimestamp, serverTimestamp, message) {
+          super(message);
+          if (Error.captureStackTrace) {
+              Error.captureStackTrace(this, ServerWasFlushedError);
+          }
+          this.clientTimestamp = clientTimestamp;
+          this.serverTimestamp = serverTimestamp;
+      }
+  }
+  function createUUIDSchema() {
+      return {
+          generate() {
+              return uuid4();
+          },
+          validate(id) {
+              return typeof id == "string" && RE_RECORD_ID.test(id);
+          },
+      };
+  }
+  function markStatus(record, status) {
+      return Object.assign(Object.assign({}, record), { _status: status });
+  }
+  function markDeleted(record) {
+      return markStatus(record, "deleted");
+  }
+  function markSynced(record) {
+      return markStatus(record, "synced");
+  }
+  /**
+   * Import a remote change into the local database.
+   *
+   * @param  {IDBTransactionProxy} transaction The transaction handler.
+   * @param  {Object}              remote      The remote change object to import.
+   * @param  {Array<String>}       localFields The list of fields that remain local.
+   * @param  {String}              strategy    The {@link Collection.strategy}.
+   * @return {Object}
+   */
+  function importChange(transaction, remote, localFields, strategy) {
+      const local = transaction.get(remote.id);
+      if (!local) {
+          // Not found locally but remote change is marked as deleted; skip to
+          // avoid recreation.
+          if (remote.deleted) {
+              return { type: "skipped", data: remote };
+          }
+          const synced = markSynced(remote);
+          transaction.create(synced);
+          return { type: "created", data: synced };
+      }
+      // Apply remote changes on local record.
+      const synced = Object.assign(Object.assign({}, local), markSynced(remote));
+      // With pull only, we don't need to compare records since we override them.
+      if (strategy === Collection.strategy.PULL_ONLY) {
+          if (remote.deleted) {
+              transaction.delete(remote.id);
+              return { type: "deleted", data: local };
+          }
+          transaction.update(synced);
+          return { type: "updated", data: { old: local, new: synced } };
+      }
+      // With other sync strategies, we detect conflicts,
+      // by comparing local and remote, ignoring local fields.
+      const isIdentical = recordsEqual(local, remote, localFields);
+      // Detect or ignore conflicts if record has also been modified locally.
+      if (local._status !== "synced") {
+          // Locally deleted, unsynced: scheduled for remote deletion.
+          if (local._status === "deleted") {
+              return { type: "skipped", data: local };
+          }
+          if (isIdentical) {
+              // If records are identical, import anyway, so we bump the
+              // local last_modified value from the server and set record
+              // status to "synced".
+              transaction.update(synced);
+              return { type: "updated", data: { old: local, new: synced } };
+          }
+          if (local.last_modified !== undefined &&
+              local.last_modified === remote.last_modified) {
+              // If our local version has the same last_modified as the remote
+              // one, this represents an object that corresponds to a resolved
+              // conflict. Our local version represents the final output, so
+              // we keep that one. (No transaction operation to do.)
+              // But if our last_modified is undefined,
+              // that means we've created the same object locally as one on
+              // the server, which *must* be a conflict.
+              return { type: "void" };
+          }
+          return {
+              type: "conflicts",
+              data: { type: "incoming", local: local, remote: remote },
+          };
+      }
+      // Local record was synced.
+      if (remote.deleted) {
+          transaction.delete(remote.id);
+          return { type: "deleted", data: local };
+      }
+      // Import locally.
+      transaction.update(synced);
+      // if identical, simply exclude it from all SyncResultObject lists
+      const type = isIdentical ? "void" : "updated";
+      return { type, data: { old: local, new: synced } };
+  }
+  /**
+   * Abstracts a collection of records stored in the local database, providing
+   * CRUD operations and synchronization helpers.
+   */
+  class Collection {
+      /**
+       * Constructor.
+       *
+       * Options:
+       * - `{BaseAdapter} adapter` The DB adapter (default: `IDB`)
+       *
+       * @param  {String}    bucket  The bucket identifier.
+       * @param  {String}    name    The collection name.
+       * @param  {KintoBase} kinto   The Kinto instance.
+       * @param  {Object}    options The options object.
+       */
+      constructor(bucket, name, kinto, options = {}) {
+          this._bucket = bucket;
+          this._name = name;
+          this._lastModified = null;
+          const DBAdapter = options.adapter || IDB;
+          if (!DBAdapter) {
+              throw new Error("No adapter provided");
+          }
+          const db = new DBAdapter(`${bucket}/${name}`, options.adapterOptions);
+          if (!(db instanceof BaseAdapter)) {
+              throw new Error("Unsupported adapter.");
+          }
+          // public properties
+          /**
+           * The db adapter instance
+           * @type {BaseAdapter}
+           */
+          this.db = db;
+          /**
+           * The KintoBase instance.
+           * @type {KintoBase}
+           */
+          this.kinto = kinto;
+          /**
+           * The event emitter instance.
+           * @type {EventEmitter}
+           */
+          this.events = options.events;
+          /**
+           * The IdSchema instance.
+           * @type {Object}
+           */
+          this.idSchema = this._validateIdSchema(options.idSchema);
+          /**
+           * The list of remote transformers.
+           * @type {Array}
+           */
+          this.remoteTransformers = this._validateRemoteTransformers(options.remoteTransformers);
+          /**
+           * The list of hooks.
+           * @type {Object}
+           */
+          this.hooks = this._validateHooks(options.hooks);
+          /**
+           * The list of fields names that will remain local.
+           * @type {Array}
+           */
+          this.localFields = options.localFields || [];
+      }
+      /**
+       * The HTTP client.
+       * @type {KintoClient}
+       */
+      get api() {
+          return this.kinto.api;
+      }
+      /**
+       * The collection name.
+       * @type {String}
+       */
+      get name() {
+          return this._name;
+      }
+      /**
+       * The bucket name.
+       * @type {String}
+       */
+      get bucket() {
+          return this._bucket;
+      }
+      /**
+       * The last modified timestamp.
+       * @type {Number}
+       */
+      get lastModified() {
+          return this._lastModified;
+      }
+      /**
+       * Synchronization strategies. Available strategies are:
+       *
+       * - `MANUAL`: Conflicts will be reported in a dedicated array.
+       * - `SERVER_WINS`: Conflicts are resolved using remote data.
+       * - `CLIENT_WINS`: Conflicts are resolved using local data.
+       *
+       * @type {Object}
+       */
+      static get strategy() {
+          return {
+              CLIENT_WINS: "client_wins",
+              SERVER_WINS: "server_wins",
+              PULL_ONLY: "pull_only",
+              MANUAL: "manual",
+          };
+      }
+      /**
+       * Validates an idSchema.
+       *
+       * @param  {Object|undefined} idSchema
+       * @return {Object}
+       */
+      _validateIdSchema(idSchema) {
+          if (typeof idSchema === "undefined") {
+              return createUUIDSchema();
+          }
+          if (typeof idSchema !== "object") {
+              throw new Error("idSchema must be an object.");
+          }
+          else if (typeof idSchema.generate !== "function") {
+              throw new Error("idSchema must provide a generate function.");
+          }
+          else if (typeof idSchema.validate !== "function") {
+              throw new Error("idSchema must provide a validate function.");
+          }
+          return idSchema;
+      }
+      /**
+       * Validates a list of remote transformers.
+       *
+       * @param  {Array|undefined} remoteTransformers
+       * @return {Array}
+       */
+      _validateRemoteTransformers(remoteTransformers) {
+          if (typeof remoteTransformers === "undefined") {
+              return [];
+          }
+          if (!Array.isArray(remoteTransformers)) {
+              throw new Error("remoteTransformers should be an array.");
+          }
+          return remoteTransformers.map(transformer => {
+              if (typeof transformer !== "object") {
+                  throw new Error("A transformer must be an object.");
+              }
+              else if (typeof transformer.encode !== "function") {
+                  throw new Error("A transformer must provide an encode function.");
+              }
+              else if (typeof transformer.decode !== "function") {
+                  throw new Error("A transformer must provide a decode function.");
+              }
+              return transformer;
+          });
+      }
+      /**
+       * Validate the passed hook is correct.
+       *
+       * @param {Array|undefined} hook.
+       * @return {Array}
+       **/
+      _validateHook(hook) {
+          if (!Array.isArray(hook)) {
+              throw new Error("A hook definition should be an array of functions.");
+          }
+          return hook.map(fn => {
+              if (typeof fn !== "function") {
+                  throw new Error("A hook definition should be an array of functions.");
+              }
+              return fn;
+          });
+      }
+      /**
+       * Validates a list of hooks.
+       *
+       * @param  {Object|undefined} hooks
+       * @return {Object}
+       */
+      _validateHooks(hooks) {
+          if (typeof hooks === "undefined") {
+              return {};
+          }
+          if (Array.isArray(hooks)) {
+              throw new Error("hooks should be an object, not an array.");
+          }
+          if (typeof hooks !== "object") {
+              throw new Error("hooks should be an object.");
+          }
+          const validatedHooks = {};
+          for (const hook in hooks) {
+              if (!AVAILABLE_HOOKS.includes(hook)) {
+                  throw new Error("The hook should be one of " + AVAILABLE_HOOKS.join(", "));
+              }
+              validatedHooks[hook] = this._validateHook(hooks[hook]);
+          }
+          return validatedHooks;
+      }
+      /**
+       * Deletes every records in the current collection and marks the collection as
+       * never synced.
+       *
+       * @return {Promise}
+       */
+      async clear() {
+          await this.db.clear();
+          await this.db.saveMetadata(null);
+          await this.db.saveLastModified(null);
+          return { data: [], permissions: {} };
+      }
+      /**
+       * Encodes a record.
+       *
+       * @param  {String} type   Either "remote" or "local".
+       * @param  {Object} record The record object to encode.
+       * @return {Promise}
+       */
+      _encodeRecord(type, record) {
+          if (!this[`${type}Transformers`].length) {
+              return Promise.resolve(record);
+          }
+          return waterfall(this[`${type}Transformers`].map(transformer => {
+              return record => transformer.encode(record);
+          }), record);
+      }
+      /**
+       * Decodes a record.
+       *
+       * @param  {String} type   Either "remote" or "local".
+       * @param  {Object} record The record object to decode.
+       * @return {Promise}
+       */
+      _decodeRecord(type, record) {
+          if (!this[`${type}Transformers`].length) {
+              return Promise.resolve(record);
+          }
+          return waterfall(this[`${type}Transformers`].reverse().map(transformer => {
+              return record => transformer.decode(record);
+          }), record);
+      }
+      /**
+       * Adds a record to the local database, asserting that none
+       * already exist with this ID.
+       *
+       * Note: If either the `useRecordId` or `synced` options are true, then the
+       * record object must contain the id field to be validated. If none of these
+       * options are true, an id is generated using the current IdSchema; in this
+       * case, the record passed must not have an id.
+       *
+       * Options:
+       * - {Boolean} synced       Sets record status to "synced" (default: `false`).
+       * - {Boolean} useRecordId  Forces the `id` field from the record to be used,
+       *                          instead of one that is generated automatically
+       *                          (default: `false`).
+       *
+       * @param  {Object} record
+       * @param  {Object} options
+       * @return {Promise}
+       */
+      create(record, options = { useRecordId: false, synced: false }) {
+          // Validate the record and its ID (if any), even though this
+          // validation is also done in the CollectionTransaction method,
+          // because we need to pass the ID to preloadIds.
+          const reject = msg => Promise.reject(new Error(msg));
+          if (typeof record !== "object") {
+              return reject("Record is not an object.");
+          }
+          if ((options.synced || options.useRecordId) &&
+              !Object.prototype.hasOwnProperty.call(record, "id")) {
+              return reject("Missing required Id; synced and useRecordId options require one");
+          }
+          if (!options.synced &&
+              !options.useRecordId &&
+              Object.prototype.hasOwnProperty.call(record, "id")) {
+              return reject("Extraneous Id; can't create a record having one set.");
+          }
+          const newRecord = Object.assign(Object.assign({}, record), { id: options.synced || options.useRecordId
+                  ? record.id
+                  : this.idSchema.generate(record), _status: options.synced ? "synced" : "created" });
+          if (!this.idSchema.validate(newRecord.id)) {
+              return reject(`Invalid Id: ${newRecord.id}`);
+          }
+          return this.execute(txn => txn.create(newRecord), {
+              preloadIds: [newRecord.id],
+          }).catch(err => {
+              if (options.useRecordId) {
+                  throw new Error("Couldn't create record. It may have been virtually deleted.");
+              }
+              throw err;
+          });
+      }
+      /**
+       * Like {@link CollectionTransaction#update}, but wrapped in its own transaction.
+       *
+       * Options:
+       * - {Boolean} synced: Sets record status to "synced" (default: false)
+       * - {Boolean} patch:  Extends the existing record instead of overwriting it
+       *   (default: false)
+       *
+       * @param  {Object} record
+       * @param  {Object} options
+       * @return {Promise}
+       */
+      update(record, options = { synced: false, patch: false }) {
+          // Validate the record and its ID, even though this validation is
+          // also done in the CollectionTransaction method, because we need
+          // to pass the ID to preloadIds.
+          if (typeof record !== "object") {
+              return Promise.reject(new Error("Record is not an object."));
+          }
+          if (!Object.prototype.hasOwnProperty.call(record, "id")) {
+              return Promise.reject(new Error("Cannot update a record missing id."));
+          }
+          if (!this.idSchema.validate(record.id)) {
+              return Promise.reject(new Error(`Invalid Id: ${record.id}`));
+          }
+          return this.execute(txn => txn.update(record, options), {
+              preloadIds: [record.id],
+          });
+      }
+      /**
+       * Like {@link CollectionTransaction#upsert}, but wrapped in its own transaction.
+       *
+       * @param  {Object} record
+       * @return {Promise}
+       */
+      upsert(record) {
+          // Validate the record and its ID, even though this validation is
+          // also done in the CollectionTransaction method, because we need
+          // to pass the ID to preloadIds.
+          if (typeof record !== "object") {
+              return Promise.reject(new Error("Record is not an object."));
+          }
+          if (!Object.prototype.hasOwnProperty.call(record, "id")) {
+              return Promise.reject(new Error("Cannot update a record missing id."));
+          }
+          if (!this.idSchema.validate(record.id)) {
+              return Promise.reject(new Error(`Invalid Id: ${record.id}`));
+          }
+          return this.execute(txn => txn.upsert(record), { preloadIds: [record.id] });
+      }
+      /**
+       * Like {@link CollectionTransaction#get}, but wrapped in its own transaction.
+       *
+       * Options:
+       * - {Boolean} includeDeleted: Include virtually deleted records.
+       *
+       * @param  {String} id
+       * @param  {Object} options
+       * @return {Promise}
+       */
+      get(id, options = { includeDeleted: false }) {
+          return this.execute(txn => txn.get(id, options), { preloadIds: [id] });
+      }
+      /**
+       * Like {@link CollectionTransaction#getAny}, but wrapped in its own transaction.
+       *
+       * @param  {String} id
+       * @return {Promise}
+       */
+      getAny(id) {
+          return this.execute(txn => txn.getAny(id), { preloadIds: [id] });
+      }
+      /**
+       * Same as {@link Collection#delete}, but wrapped in its own transaction.
+       *
+       * Options:
+       * - {Boolean} virtual: When set to `true`, doesn't actually delete the record,
+       *   update its `_status` attribute to `deleted` instead (default: true)
+       *
+       * @param  {String} id       The record's Id.
+       * @param  {Object} options  The options object.
+       * @return {Promise}
+       */
+      delete(id, options = { virtual: true }) {
+          return this.execute(transaction => {
+              return transaction.delete(id, options);
+          }, { preloadIds: [id] });
+      }
+      /**
+       * Same as {@link Collection#deleteAll}, but wrapped in its own transaction, execulding the parameter.
+       *
+       * @return {Promise}
+       */
+      async deleteAll() {
+          const { data } = await this.list({}, { includeDeleted: false });
+          const recordIds = data.map(record => record.id);
+          return this.execute(transaction => {
+              return transaction.deleteAll(recordIds);
+          }, { preloadIds: recordIds });
+      }
+      /**
+       * The same as {@link CollectionTransaction#deleteAny}, but wrapped
+       * in its own transaction.
+       *
+       * @param  {String} id       The record's Id.
+       * @return {Promise}
+       */
+      deleteAny(id) {
+          return this.execute(txn => txn.deleteAny(id), { preloadIds: [id] });
+      }
+      /**
+       * Lists records from the local database.
+       *
+       * Params:
+       * - {Object} filters Filter the results (default: `{}`).
+       * - {String} order   The order to apply   (default: `-last_modified`).
+       *
+       * Options:
+       * - {Boolean} includeDeleted: Include virtually deleted records.
+       *
+       * @param  {Object} params  The filters and order to apply to the results.
+       * @param  {Object} options The options object.
+       * @return {Promise}
+       */
+      async list(params = {}, options = { includeDeleted: false }) {
+          params = Object.assign({ order: "-last_modified", filters: {} }, params);
+          const results = await this.db.list(params);
+          let data = results;
+          if (!options.includeDeleted) {
+              data = results.filter(record => record._status !== "deleted");
+          }
+          return { data, permissions: {} };
+      }
+      /**
+       * Imports remote changes into the local database.
+       * This method is in charge of detecting the conflicts, and resolve them
+       * according to the specified strategy.
+       * @param  {SyncResultObject} syncResultObject The sync result object.
+       * @param  {Array}            decodedChanges   The list of changes to import in the local database.
+       * @param  {String}           strategy         The {@link Collection.strategy} (default: MANUAL)
+       * @return {Promise}
+       */
+      async importChanges(syncResultObject, decodedChanges, strategy = Collection.strategy.MANUAL) {
+          // Retrieve records matching change ids.
+          try {
+              for (let i = 0; i < decodedChanges.length; i += IMPORT_CHUNK_SIZE) {
+                  const slice = decodedChanges.slice(i, i + IMPORT_CHUNK_SIZE);
+                  const { imports, resolved } = await this.db.execute(transaction => {
+                      const imports = slice.map(remote => {
+                          // Store remote change into local database.
+                          return importChange(transaction, remote, this.localFields, strategy);
+                      });
+                      const conflicts = imports
+                          .filter(i => i.type === "conflicts")
+                          .map(i => i.data);
+                      const resolved = this._handleConflicts(transaction, conflicts, strategy);
+                      return { imports, resolved };
+                  }, { preload: slice.map(record => record.id) });
+                  // Lists of created/updated/deleted records
+                  imports.forEach(({ type, data }) => syncResultObject.add(type, data));
+                  // Automatically resolved conflicts (if not manual)
+                  if (resolved.length > 0) {
+                      syncResultObject.reset("conflicts").add("resolved", resolved);
+                  }
+              }
+          }
+          catch (err) {
+              const data = {
+                  type: "incoming",
+                  message: err.message,
+                  stack: err.stack,
+              };
+              // XXX one error of the whole transaction instead of per atomic op
+              syncResultObject.add("errors", data);
+          }
+          return syncResultObject;
+      }
+      /**
+       * Imports the responses of pushed changes into the local database.
+       * Basically it stores the timestamp assigned by the server into the local
+       * database.
+       * @param  {SyncResultObject} syncResultObject The sync result object.
+       * @param  {Array}            toApplyLocally   The list of changes to import in the local database.
+       * @param  {Array}            conflicts        The list of conflicts that have to be resolved.
+       * @param  {String}           strategy         The {@link Collection.strategy}.
+       * @return {Promise}
+       */
+      async _applyPushedResults(syncResultObject, toApplyLocally, conflicts, strategy = Collection.strategy.MANUAL) {
+          const toDeleteLocally = toApplyLocally.filter(r => r.deleted);
+          const toUpdateLocally = toApplyLocally.filter(r => !r.deleted);
+          const { published, resolved } = await this.db.execute(transaction => {
+              const updated = toUpdateLocally.map(record => {
+                  const synced = markSynced(record);
+                  transaction.update(synced);
+                  return synced;
+              });
+              const deleted = toDeleteLocally.map(record => {
+                  transaction.delete(record.id);
+                  // Amend result data with the deleted attribute set
+                  return { id: record.id, deleted: true };
+              });
+              const published = updated.concat(deleted);
+              // Handle conflicts, if any
+              const resolved = this._handleConflicts(transaction, conflicts, strategy);
+              return { published, resolved };
+          });
+          syncResultObject.add("published", published);
+          if (resolved.length > 0) {
+              syncResultObject
+                  .reset("conflicts")
+                  .reset("resolved")
+                  .add("resolved", resolved);
+          }
+          return syncResultObject;
+      }
+      /**
+       * Handles synchronization conflicts according to specified strategy.
+       *
+       * @param  {SyncResultObject} result    The sync result object.
+       * @param  {String}           strategy  The {@link Collection.strategy}.
+       * @return {Promise<Array<Object>>} The resolved conflicts, as an
+       *    array of {accepted, rejected} objects
+       */
+      _handleConflicts(transaction, conflicts, strategy) {
+          if (strategy === Collection.strategy.MANUAL) {
+              return [];
+          }
+          return conflicts.map(conflict => {
+              const resolution = strategy === Collection.strategy.CLIENT_WINS
+                  ? conflict.local
+                  : conflict.remote;
+              const rejected = strategy === Collection.strategy.CLIENT_WINS
+                  ? conflict.remote
+                  : conflict.local;
+              let accepted, status, id;
+              if (resolution === null) {
+                  // We "resolved" with the server-side deletion. Delete locally.
+                  // This only happens during SERVER_WINS because the local
+                  // version of a record can never be null.
+                  // We can get "null" from the remote side if we got a conflict
+                  // and there is no remote version available; see kinto-http.js
+                  // batch.js:aggregate.
+                  transaction.delete(conflict.local.id);
+                  accepted = null;
+                  // The record was deleted, but that status is "synced" with
+                  // the server, so we don't need to push the change.
+                  status = "synced";
+                  id = conflict.local.id;
+              }
+              else {
+                  const updated = this._resolveRaw(conflict, resolution);
+                  transaction.update(updated);
+                  accepted = updated;
+                  status = updated._status;
+                  id = updated.id;
+              }
+              return { rejected, accepted, id, _status: status };
+          });
+      }
+      /**
+       * Execute a bunch of operations in a transaction.
+       *
+       * This transaction should be atomic -- either all of its operations
+       * will succeed, or none will.
+       *
+       * The argument to this function is itself a function which will be
+       * called with a {@link CollectionTransaction}. Collection methods
+       * are available on this transaction, but instead of returning
+       * promises, they are synchronous. execute() returns a Promise whose
+       * value will be the return value of the provided function.
+       *
+       * Most operations will require access to the record itself, which
+       * must be preloaded by passing its ID in the preloadIds option.
+       *
+       * Options:
+       * - {Array} preloadIds: list of IDs to fetch at the beginning of
+       *   the transaction
+       *
+       * @return {Promise} Resolves with the result of the given function
+       *    when the transaction commits.
+       */
+      execute(doOperations, { preloadIds = [] } = {}) {
+          for (const id of preloadIds) {
+              if (!this.idSchema.validate(id)) {
+                  return Promise.reject(Error(`Invalid Id: ${id}`));
+              }
+          }
+          return this.db.execute(transaction => {
+              const txn = new CollectionTransaction(this, transaction);
+              const result = doOperations(txn);
+              txn.emitEvents();
+              return result;
+          }, { preload: preloadIds });
+      }
+      /**
+       * Resets the local records as if they were never synced; existing records are
+       * marked as newly created, deleted records are dropped.
+       *
+       * A next call to {@link Collection.sync} will thus republish the whole
+       * content of the local collection to the server.
+       *
+       * @return {Promise} Resolves with the number of processed records.
+       */
+      async resetSyncStatus() {
+          const unsynced = await this.list({ filters: { _status: ["deleted", "synced"] }, order: "" }, { includeDeleted: true });
+          await this.db.execute(transaction => {
+              unsynced.data.forEach(record => {
+                  if (record._status === "deleted") {
+                      // Garbage collect deleted records.
+                      transaction.delete(record.id);
+                  }
+                  else {
+                      // Records that were synced become «created».
+                      transaction.update(Object.assign(Object.assign({}, record), { last_modified: undefined, _status: "created" }));
+                  }
+              });
+          });
+          this._lastModified = null;
+          await this.db.saveLastModified(null);
+          return unsynced.data.length;
+      }
+      /**
+       * Returns an object containing two lists:
+       *
+       * - `toDelete`: unsynced deleted records we can safely delete;
+       * - `toSync`: local updates to send to the server.
+       *
+       * @return {Promise}
+       */
+      async gatherLocalChanges() {
+          const unsynced = await this.list({
+              filters: { _status: ["created", "updated"] },
+              order: "",
+          });
+          const deleted = await this.list({ filters: { _status: "deleted" }, order: "" }, { includeDeleted: true });
+          return await Promise.all(unsynced.data
+              .concat(deleted.data)
+              .map(this._encodeRecord.bind(this, "remote")));
+      }
+      /**
+       * Fetch remote changes, import them to the local database, and handle
+       * conflicts according to `options.strategy`. Then, updates the passed
+       * {@link SyncResultObject} with import results.
+       *
+       * Options:
+       * - {String} strategy: The selected sync strategy.
+       * - {String} expectedTimestamp: A timestamp to use as a "cache busting" query parameter.
+       * - {Array<String>} exclude: A list of record ids to exclude from pull.
+       * - {Object} headers: The HTTP headers to use in the request.
+       * - {int} retry: The number of retries to do if the HTTP request fails.
+       * - {int} lastModified: The timestamp to use in `?_since` query.
+       *
+       * @param  {KintoClient.Collection} client           Kinto client Collection instance.
+       * @param  {SyncResultObject}       syncResultObject The sync result object.
+       * @param  {Object}                 options          The options object.
+       * @return {Promise}
+       */
+      async pullChanges(client, syncResultObject, options = {}) {
+          if (!syncResultObject.ok) {
+              return syncResultObject;
+          }
+          const since = this.lastModified
+              ? this.lastModified
+              : await this.db.getLastModified();
+          options = Object.assign({ strategy: Collection.strategy.MANUAL, lastModified: since, headers: {} }, options);
+          // Optionally ignore some records when pulling for changes.
+          // (avoid redownloading our own changes on last step of #sync())
+          let filters;
+          if (options.exclude) {
+              // Limit the list of excluded records to the first 50 records in order
+              // to remain under de-facto URL size limit (~2000 chars).
+              // http://stackoverflow.com/questions/417142/what-is-the-maximum-length-of-a-url-in-different-browsers/417184#417184
+              const exclude_id = options.exclude
+                  .slice(0, 50)
+                  .map(r => r.id)
+                  .join(",");
+              filters = { exclude_id };
+          }
+          if (options.expectedTimestamp) {
+              filters = Object.assign(Object.assign({}, filters), { _expected: options.expectedTimestamp });
+          }
+          // First fetch remote changes from the server
+          const { data, last_modified } = await client.listRecords({
+              // Since should be ETag (see https://github.com/Kinto/kinto.js/issues/356)
+              since: options.lastModified ? `${options.lastModified}` : undefined,
+              headers: options.headers,
+              retry: options.retry,
+              // Fetch every page by default (FIXME: option to limit pages, see #277)
+              pages: Infinity,
+              filters,
+          });
+          // last_modified is the ETag header value (string).
+          // For retro-compatibility with first kinto.js versions
+          // parse it to integer.
+          const unquoted = last_modified ? parseInt(last_modified, 10) : undefined;
+          // Check if server was flushed.
+          // This is relevant for the Kinto demo server
+          // (and thus for many new comers).
+          const localSynced = options.lastModified;
+          const serverChanged = unquoted > options.lastModified;
+          const emptyCollection = data.length === 0;
+          if (!options.exclude && localSynced && serverChanged && emptyCollection) {
+              const e = new ServerWasFlushedError(localSynced, unquoted, "Server has been flushed. Client Side Timestamp: " +
+                  localSynced +
+                  " Server Side Timestamp: " +
+                  unquoted);
+              throw e;
+          }
+          // Atomic updates are not sensible here because unquoted is not
+          // computed as a function of syncResultObject.lastModified.
+          // eslint-disable-next-line require-atomic-updates
+          syncResultObject.lastModified = unquoted;
+          // Decode incoming changes.
+          const decodedChanges = await Promise.all(data.map(change => {
+              return this._decodeRecord("remote", change);
+          }));
+          // Hook receives decoded records.
+          const payload = { lastModified: unquoted, changes: decodedChanges };
+          const afterHooks = await this.applyHook("incoming-changes", payload);
+          // No change, nothing to import.
+          if (afterHooks.changes.length > 0) {
+              // Reflect these changes locally
+              await this.importChanges(syncResultObject, afterHooks.changes, options.strategy);
+          }
+          return syncResultObject;
+      }
+      applyHook(hookName, payload) {
+          if (typeof this.hooks[hookName] == "undefined") {
+              return Promise.resolve(payload);
+          }
+          return waterfall(this.hooks[hookName].map(hook => {
+              return record => {
+                  const result = hook(payload, this);
+                  const resultThenable = result && typeof result.then === "function";
+                  const resultChanges = result && Object.prototype.hasOwnProperty.call(result, "changes");
+                  if (!(resultThenable || resultChanges)) {
+                      throw new Error(`Invalid return value for hook: ${JSON.stringify(result)} has no 'then()' or 'changes' properties`);
+                  }
+                  return result;
+              };
+          }), payload);
+      }
+      /**
+       * Publish local changes to the remote server and updates the passed
+       * {@link SyncResultObject} with publication results.
+       *
+       * Options:
+       * - {String} strategy: The selected sync strategy.
+       * - {Object} headers: The HTTP headers to use in the request.
+       * - {int} retry: The number of retries to do if the HTTP request fails.
+       *
+       * @param  {KintoClient.Collection} client           Kinto client Collection instance.
+       * @param  {SyncResultObject}       syncResultObject The sync result object.
+       * @param  {Object}                 changes          The change object.
+       * @param  {Array}                  changes.toDelete The list of records to delete.
+       * @param  {Array}                  changes.toSync   The list of records to create/update.
+       * @param  {Object}                 options          The options object.
+       * @return {Promise}
+       */
+      async pushChanges(client, changes, syncResultObject, options = {}) {
+          if (!syncResultObject.ok) {
+              return syncResultObject;
+          }
+          const safe = !options.strategy || options.strategy !== Collection.CLIENT_WINS;
+          const toDelete = changes.filter(r => r._status == "deleted");
+          const toSync = changes.filter(r => r._status != "deleted");
+          // Perform a batch request with every changes.
+          const synced = await client.batch(batch => {
+              toDelete.forEach(r => {
+                  // never published locally deleted records should not be pusblished
+                  if (r.last_modified) {
+                      batch.deleteRecord(r);
+                  }
+              });
+              toSync.forEach(r => {
+                  // Clean local fields (like _status) before sending to server.
+                  const published = this.cleanLocalFields(r);
+                  if (r._status === "created") {
+                      batch.createRecord(published);
+                  }
+                  else {
+                      batch.updateRecord(published);
+                  }
+              });
+          }, {
+              headers: options.headers,
+              retry: options.retry,
+              safe,
+              aggregate: true,
+          });
+          // Store outgoing errors into sync result object
+          syncResultObject.add("errors", synced.errors.map(e => (Object.assign(Object.assign({}, e), { type: "outgoing" }))));
+          // Store outgoing conflicts into sync result object
+          const conflicts = [];
+          for (const { type, local, remote } of synced.conflicts) {
+              // Note: we ensure that local data are actually available, as they may
+              // be missing in the case of a published deletion.
+              const safeLocal = (local && local.data) || { id: remote.id };
+              const realLocal = await this._decodeRecord("remote", safeLocal);
+              // We can get "null" from the remote side if we got a conflict
+              // and there is no remote version available; see kinto-http.js
+              // batch.js:aggregate.
+              const realRemote = remote && (await this._decodeRecord("remote", remote));
+              const conflict = { type, local: realLocal, remote: realRemote };
+              conflicts.push(conflict);
+          }
+          syncResultObject.add("conflicts", conflicts);
+          // Records that must be deleted are either deletions that were pushed
+          // to server (published) or deleted records that were never pushed (skipped).
+          const missingRemotely = synced.skipped.map(r => (Object.assign(Object.assign({}, r), { deleted: true })));
+          // For created and updated records, the last_modified coming from server
+          // will be stored locally.
+          // Reflect publication results locally using the response from
+          // the batch request.
+          const published = synced.published.map(c => c.data);
+          const toApplyLocally = published.concat(missingRemotely);
+          // Apply the decode transformers, if any
+          const decoded = await Promise.all(toApplyLocally.map(record => {
+              return this._decodeRecord("remote", record);
+          }));
+          // We have to update the local records with the responses of the server
+          // (eg. last_modified values etc.).
+          if (decoded.length > 0 || conflicts.length > 0) {
+              await this._applyPushedResults(syncResultObject, decoded, conflicts, options.strategy);
+          }
+          return syncResultObject;
+      }
+      /**
+       * Return a copy of the specified record without the local fields.
+       *
+       * @param  {Object} record  A record with potential local fields.
+       * @return {Object}
+       */
+      cleanLocalFields(record) {
+          const localKeys = RECORD_FIELDS_TO_CLEAN.concat(this.localFields);
+          return omitKeys(record, localKeys);
+      }
+      /**
+       * Resolves a conflict, updating local record according to proposed
+       * resolution — keeping remote record `last_modified` value as a reference for
+       * further batch sending.
+       *
+       * @param  {Object} conflict   The conflict object.
+       * @param  {Object} resolution The proposed record.
+       * @return {Promise}
+       */
+      resolve(conflict, resolution) {
+          return this.db.execute(transaction => {
+              const updated = this._resolveRaw(conflict, resolution);
+              transaction.update(updated);
+              return { data: updated, permissions: {} };
+          });
+      }
+      /**
+       * @private
+       */
+      _resolveRaw(conflict, resolution) {
+          const resolved = Object.assign(Object.assign({}, resolution), {
+              // Ensure local record has the latest authoritative timestamp
+              last_modified: conflict.remote && conflict.remote.last_modified });
+          // If the resolution object is strictly equal to the
+          // remote record, then we can mark it as synced locally.
+          // Otherwise, mark it as updated (so that the resolution is pushed).
+          const synced = deepEqual(resolved, conflict.remote);
+          return markStatus(resolved, synced ? "synced" : "updated");
+      }
+      /**
+       * Synchronize remote and local data. The promise will resolve with a
+       * {@link SyncResultObject}, though will reject:
+       *
+       * - if the server is currently backed off;
+       * - if the server has been detected flushed.
+       *
+       * Options:
+       * - {Object} headers: HTTP headers to attach to outgoing requests.
+       * - {String} expectedTimestamp: A timestamp to use as a "cache busting" query parameter.
+       * - {Number} retry: Number of retries when server fails to process the request (default: 1).
+       * - {Collection.strategy} strategy: See {@link Collection.strategy}.
+       * - {Boolean} ignoreBackoff: Force synchronization even if server is currently
+       *   backed off.
+       * - {String} bucket: The remove bucket id to use (default: null)
+       * - {String} collection: The remove collection id to use (default: null)
+       * - {String} remote The remote Kinto server endpoint to use (default: null).
+       *
+       * @param  {Object} options Options.
+       * @return {Promise}
+       * @throws {Error} If an invalid remote option is passed.
+       */
+      async sync(options = {
+          strategy: Collection.strategy.MANUAL,
+          headers: {},
+          retry: 1,
+          ignoreBackoff: false,
+          bucket: null,
+          collection: null,
+          remote: null,
+          expectedTimestamp: null,
+      }) {
+          options = Object.assign(Object.assign({}, options), { bucket: options.bucket || this.bucket, collection: options.collection || this.name });
+          const previousRemote = this.api.remote;
+          if (options.remote) {
+              // Note: setting the remote ensures it's valid, throws when invalid.
+              this.api.remote = options.remote;
+          }
+          if (!options.ignoreBackoff && this.api.backoff > 0) {
+              const seconds = Math.ceil(this.api.backoff / 1000);
+              return Promise.reject(new Error(`Server is asking clients to back off; retry in ${seconds}s or use the ignoreBackoff option.`));
+          }
+          const client = this.api
+              .bucket(options.bucket)
+              .collection(options.collection);
+          const result = new SyncResultObject();
+          try {
+              // Fetch collection metadata.
+              await this.pullMetadata(client, options);
+              // Fetch last changes from the server.
+              await this.pullChanges(client, result, options);
+              const { lastModified } = result;
+              if (options.strategy != Collection.strategy.PULL_ONLY) {
+                  // Fetch local changes
+                  const toSync = await this.gatherLocalChanges();
+                  // Publish local changes and pull local resolutions
+                  await this.pushChanges(client, toSync, result, options);
+                  // Publish local resolution of push conflicts to server (on CLIENT_WINS)
+                  const resolvedUnsynced = result.resolved.filter(r => r._status !== "synced");
+                  if (resolvedUnsynced.length > 0) {
+                      const resolvedEncoded = await Promise.all(resolvedUnsynced.map(resolution => {
+                          let record = resolution.accepted;
+                          if (record === null) {
+                              record = { id: resolution.id, _status: resolution._status };
+                          }
+                          return this._encodeRecord("remote", record);
+                      }));
+                      await this.pushChanges(client, resolvedEncoded, result, options);
+                  }
+                  // Perform a last pull to catch changes that occured after the last pull,
+                  // while local changes were pushed. Do not do it nothing was pushed.
+                  if (result.published.length > 0) {
+                      // Avoid redownloading our own changes during the last pull.
+                      const pullOpts = Object.assign(Object.assign({}, options), { lastModified, exclude: result.published });
+                      await this.pullChanges(client, result, pullOpts);
+                  }
+              }
+              // Don't persist lastModified value if any conflict or error occured
+              if (result.ok) {
+                  // No conflict occured, persist collection's lastModified value
+                  this._lastModified = await this.db.saveLastModified(result.lastModified);
+              }
+          }
+          catch (e) {
+              this.events.emit("sync:error", Object.assign(Object.assign({}, options), { error: e }));
+              throw e;
+          }
+          finally {
+              // Ensure API default remote is reverted if a custom one's been used
+              this.api.remote = previousRemote;
+          }
+          this.events.emit("sync:success", Object.assign(Object.assign({}, options), { result }));
+          return result;
+      }
+      /**
+       * Load a list of records already synced with the remote server.
+       *
+       * The local records which are unsynced or whose timestamp is either missing
+       * or superior to those being loaded will be ignored.
+       *
+       * @deprecated Use {@link importBulk} instead.
+       * @param  {Array} records The previously exported list of records to load.
+       * @return {Promise} with the effectively imported records.
+       */
+      async loadDump(records) {
+          return this.importBulk(records);
+      }
+      /**
+       * Load a list of records already synced with the remote server.
+       *
+       * The local records which are unsynced or whose timestamp is either missing
+       * or superior to those being loaded will be ignored.
+       *
+       * @param  {Array} records The previously exported list of records to load.
+       * @return {Promise} with the effectively imported records.
+       */
+      async importBulk(records) {
+          if (!Array.isArray(records)) {
+              throw new Error("Records is not an array.");
+          }
+          for (const record of records) {
+              if (!Object.prototype.hasOwnProperty.call(record, "id") ||
+                  !this.idSchema.validate(record.id)) {
+                  throw new Error("Record has invalid ID: " + JSON.stringify(record));
+              }
+              if (!record.last_modified) {
+                  throw new Error("Record has no last_modified value: " + JSON.stringify(record));
+              }
+          }
+          // Fetch all existing records from local database,
+          // and skip those who are newer or not marked as synced.
+          // XXX filter by status / ids in records
+          const { data } = await this.list({}, { includeDeleted: true });
+          const existingById = data.reduce((acc, record) => {
+              acc[record.id] = record;
+              return acc;
+          }, {});
+          const newRecords = records.filter(record => {
+              const localRecord = existingById[record.id];
+              const shouldKeep =
+              // No local record with this id.
+              localRecord === undefined ||
+                  // Or local record is synced
+                  (localRecord._status === "synced" &&
+                      // And was synced from server
+                      localRecord.last_modified !== undefined &&
+                      // And is older than imported one.
+                      record.last_modified > localRecord.last_modified);
+              return shouldKeep;
+          });
+          return await this.db.importBulk(newRecords.map(markSynced));
+      }
+      async pullMetadata(client, options = {}) {
+          const { expectedTimestamp, headers } = options;
+          const query = expectedTimestamp
+              ? { query: { _expected: expectedTimestamp } }
+              : undefined;
+          const metadata = await client.getData(Object.assign(Object.assign({}, query), { headers }));
+          return this.db.saveMetadata(metadata);
+      }
+      async metadata() {
+          return this.db.getMetadata();
+      }
+  }
+  /**
+   * A Collection-oriented wrapper for an adapter's transaction.
+   *
+   * This defines the high-level functions available on a collection.
+   * The collection itself offers functions of the same name. These will
+   * perform just one operation in its own transaction.
+   */
+  class CollectionTransaction {
+      constructor(collection, adapterTransaction) {
+          this.collection = collection;
+          this.adapterTransaction = adapterTransaction;
+          this._events = [];
+      }
+      _queueEvent(action, payload) {
+          this._events.push({ action, payload });
+      }
+      /**
+       * Emit queued events, to be called once every transaction operations have
+       * been executed successfully.
+       */
+      emitEvents() {
+          for (const { action, payload } of this._events) {
+              this.collection.events.emit(action, payload);
+          }
+          if (this._events.length > 0) {
+              const targets = this._events.map(({ action, payload }) => (Object.assign({ action }, payload)));
+              this.collection.events.emit("change", { targets });
+          }
+          this._events = [];
+      }
+      /**
+       * Retrieve a record by its id from the local database, or
+       * undefined if none exists.
+       *
+       * This will also return virtually deleted records.
+       *
+       * @param  {String} id
+       * @return {Object}
+       */
+      getAny(id) {
+          const record = this.adapterTransaction.get(id);
+          return { data: record, permissions: {} };
+      }
+      /**
+       * Retrieve a record by its id from the local database.
+       *
+       * Options:
+       * - {Boolean} includeDeleted: Include virtually deleted records.
+       *
+       * @param  {String} id
+       * @param  {Object} options
+       * @return {Object}
+       */
+      get(id, options = { includeDeleted: false }) {
+          const res = this.getAny(id);
+          if (!res.data ||
+              (!options.includeDeleted && res.data._status === "deleted")) {
+              throw new Error(`Record with id=${id} not found.`);
+          }
+          return res;
+      }
+      /**
+       * Deletes a record from the local database.
+       *
+       * Options:
+       * - {Boolean} virtual: When set to `true`, doesn't actually delete the record,
+       *   update its `_status` attribute to `deleted` instead (default: true)
+       *
+       * @param  {String} id       The record's Id.
+       * @param  {Object} options  The options object.
+       * @return {Object}
+       */
+      delete(id, options = { virtual: true }) {
+          // Ensure the record actually exists.
+          const existing = this.adapterTransaction.get(id);
+          const alreadyDeleted = existing && existing._status == "deleted";
+          if (!existing || (alreadyDeleted && options.virtual)) {
+              throw new Error(`Record with id=${id} not found.`);
+          }
+          // Virtual updates status.
+          if (options.virtual) {
+              this.adapterTransaction.update(markDeleted(existing));
+          }
+          else {
+              // Delete for real.
+              this.adapterTransaction.delete(id);
+          }
+          this._queueEvent("delete", { data: existing });
+          return { data: existing, permissions: {} };
+      }
+      /**
+       * Soft delete all records from the local database.
+       *
+       * @param  {Array} ids        Array of non-deleted Record Ids.
+       * @return {Object}
+       */
+      deleteAll(ids) {
+          const existingRecords = [];
+          ids.forEach(id => {
+              existingRecords.push(this.adapterTransaction.get(id));
+              this.delete(id);
+          });
+          this._queueEvent("deleteAll", { data: existingRecords });
+          return { data: existingRecords, permissions: {} };
+      }
+      /**
+       * Deletes a record from the local database, if any exists.
+       * Otherwise, do nothing.
+       *
+       * @param  {String} id       The record's Id.
+       * @return {Object}
+       */
+      deleteAny(id) {
+          const existing = this.adapterTransaction.get(id);
+          if (existing) {
+              this.adapterTransaction.update(markDeleted(existing));
+              this._queueEvent("delete", { data: existing });
+          }
+          return { data: Object.assign({ id }, existing), deleted: !!existing, permissions: {} };
+      }
+      /**
+       * Adds a record to the local database, asserting that none
+       * already exist with this ID.
+       *
+       * @param  {Object} record, which must contain an ID
+       * @return {Object}
+       */
+      create(record) {
+          if (typeof record !== "object") {
+              throw new Error("Record is not an object.");
+          }
+          if (!Object.prototype.hasOwnProperty.call(record, "id")) {
+              throw new Error("Cannot create a record missing id");
+          }
+          if (!this.collection.idSchema.validate(record.id)) {
+              throw new Error(`Invalid Id: ${record.id}`);
+          }
+          this.adapterTransaction.create(record);
+          this._queueEvent("create", { data: record });
+          return { data: record, permissions: {} };
+      }
+      /**
+       * Updates a record from the local database.
+       *
+       * Options:
+       * - {Boolean} synced: Sets record status to "synced" (default: false)
+       * - {Boolean} patch:  Extends the existing record instead of overwriting it
+       *   (default: false)
+       *
+       * @param  {Object} record
+       * @param  {Object} options
+       * @return {Object}
+       */
+      update(record, options = { synced: false, patch: false }) {
+          if (typeof record !== "object") {
+              throw new Error("Record is not an object.");
+          }
+          if (!Object.prototype.hasOwnProperty.call(record, "id")) {
+              throw new Error("Cannot update a record missing id.");
+          }
+          if (!this.collection.idSchema.validate(record.id)) {
+              throw new Error(`Invalid Id: ${record.id}`);
+          }
+          const oldRecord = this.adapterTransaction.get(record.id);
+          if (!oldRecord) {
+              throw new Error(`Record with id=${record.id} not found.`);
+          }
+          const newRecord = options.patch ? Object.assign(Object.assign({}, oldRecord), record) : record;
+          const updated = this._updateRaw(oldRecord, newRecord, options);
+          this.adapterTransaction.update(updated);
+          this._queueEvent("update", { data: updated, oldRecord });
+          return { data: updated, oldRecord, permissions: {} };
+      }
+      /**
+       * Lower-level primitive for updating a record while respecting
+       * _status and last_modified.
+       *
+       * @param  {Object} oldRecord: the record retrieved from the DB
+       * @param  {Object} newRecord: the record to replace it with
+       * @return {Object}
+       */
+      _updateRaw(oldRecord, newRecord, { synced = false } = {}) {
+          const updated = Object.assign({}, newRecord);
+          // Make sure to never loose the existing timestamp.
+          if (oldRecord && oldRecord.last_modified && !updated.last_modified) {
+              updated.last_modified = oldRecord.last_modified;
+          }
+          // If only local fields have changed, then keep record as synced.
+          // If status is created, keep record as created.
+          // If status is deleted, mark as updated.
+          const isIdentical = oldRecord &&
+              recordsEqual(oldRecord, updated, this.collection.localFields);
+          const keepSynced = isIdentical && oldRecord._status == "synced";
+          const neverSynced = !oldRecord || (oldRecord && oldRecord._status == "created");
+          const newStatus = keepSynced || synced ? "synced" : neverSynced ? "created" : "updated";
+          return markStatus(updated, newStatus);
+      }
+      /**
+       * Upsert a record into the local database.
+       *
+       * This record must have an ID.
+       *
+       * If a record with this ID already exists, it will be replaced.
+       * Otherwise, this record will be inserted.
+       *
+       * @param  {Object} record
+       * @return {Object}
+       */
+      upsert(record) {
+          if (typeof record !== "object") {
+              throw new Error("Record is not an object.");
+          }
+          if (!Object.prototype.hasOwnProperty.call(record, "id")) {
+              throw new Error("Cannot update a record missing id.");
+          }
+          if (!this.collection.idSchema.validate(record.id)) {
+              throw new Error(`Invalid Id: ${record.id}`);
+          }
+          let oldRecord = this.adapterTransaction.get(record.id);
+          const updated = this._updateRaw(oldRecord, record);
+          this.adapterTransaction.update(updated);
+          // Don't return deleted records -- pretend they are gone
+          if (oldRecord && oldRecord._status == "deleted") {
+              oldRecord = undefined;
+          }
+          if (oldRecord) {
+              this._queueEvent("update", { data: updated, oldRecord });
+          }
+          else {
+              this._queueEvent("create", { data: updated });
+          }
+          return { data: updated, oldRecord, permissions: {} };
+      }
+  }
+
+  const DEFAULT_BUCKET_NAME = "default";
+  const DEFAULT_REMOTE = "http://localhost:8888/v1";
+  const DEFAULT_RETRY = 1;
+  /**
+   * KintoBase class.
+   */
+  class KintoBase {
+      /**
+       * Provides a public access to the base adapter class. Users can create a
+       * custom DB adapter by extending {@link BaseAdapter}.
+       *
+       * @type {Object}
+       */
+      static get adapters() {
+          return {
+              BaseAdapter: BaseAdapter,
+          };
+      }
+      /**
+       * Synchronization strategies. Available strategies are:
+       *
+       * - `MANUAL`: Conflicts will be reported in a dedicated array.
+       * - `SERVER_WINS`: Conflicts are resolved using remote data.
+       * - `CLIENT_WINS`: Conflicts are resolved using local data.
+       *
+       * @type {Object}
+       */
+      static get syncStrategy() {
+          return Collection.strategy;
+      }
+      /**
+       * Constructor.
+       *
+       * Options:
+       * - `{String}`       `remote`         The server URL to use.
+       * - `{String}`       `bucket`         The collection bucket name.
+       * - `{EventEmitter}` `events`         Events handler.
+       * - `{BaseAdapter}`  `adapter`        The base DB adapter class.
+       * - `{Object}`       `adapterOptions` Options given to the adapter.
+       * - `{Object}`       `headers`        The HTTP headers to use.
+       * - `{Object}`       `retry`          Number of retries when the server fails to process the request (default: `1`)
+       * - `{String}`       `requestMode`    The HTTP CORS mode to use.
+       * - `{Number}`       `timeout`        The requests timeout in ms (default: `5000`).
+       *
+       * @param  {Object} options The options object.
+       */
+      constructor(options = {}) {
+          const defaults = {
+              bucket: DEFAULT_BUCKET_NAME,
+              remote: DEFAULT_REMOTE,
+              retry: DEFAULT_RETRY,
+          };
+          this._options = Object.assign(Object.assign({}, defaults), options);
+          if (!this._options.adapter) {
+              throw new Error("No adapter provided");
+          }
+          this._api = null;
+          /**
+           * The event emitter instance.
+           * @type {EventEmitter}
+           */
+          this.events = this._options.events;
+      }
+      /**
+       * The kinto HTTP client instance.
+       * @type {KintoClient}
+       */
+      get api() {
+          const { events, headers, remote, requestMode, retry, timeout, } = this._options;
+          if (!this._api) {
+              this._api = new this.ApiClass(remote, {
+                  events,
+                  headers,
+                  requestMode,
+                  retry,
+                  timeout,
+              });
+          }
+          return this._api;
+      }
+      /**
+       * Creates a {@link Collection} instance. The second (optional) parameter
+       * will set collection-level options like e.g. `remoteTransformers`.
+       *
+       * @param  {String} collName The collection name.
+       * @param  {Object} [options={}]                 Extra options or override client's options.
+       * @param  {Object} [options.idSchema]           IdSchema instance (default: UUID)
+       * @param  {Object} [options.remoteTransformers] Array<RemoteTransformer> (default: `[]`])
+       * @param  {Object} [options.hooks]              Array<Hook> (default: `[]`])
+       * @param  {Object} [options.localFields]        Array<Field> (default: `[]`])
+       * @return {Collection}
+       */
+      collection(collName, options = {}) {
+          if (!collName) {
+              throw new Error("missing collection name");
+          }
+          const { bucket, events, adapter, adapterOptions } = Object.assign(Object.assign({}, this._options), options);
+          const { idSchema, remoteTransformers, hooks, localFields } = options;
+          return new Collection(bucket, collName, this, {
+              events,
+              adapter,
+              adapterOptions,
+              idSchema,
+              remoteTransformers,
+              hooks,
+              localFields,
+          });
+      }
+  }
+
+  /*
+   *
+   * Licensed under the Apache License, Version 2.0 (the "License");
+   * you may not use this file except in compliance with the License.
+   * You may obtain a copy of the License at
+   *
+   *     http://www.apache.org/licenses/LICENSE-2.0
+   *
+   * Unless required by applicable law or agreed to in writing, software
+   * distributed under the License is distributed on an "AS IS" BASIS,
+   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   * See the License for the specific language governing permissions and
+   * limitations under the License.
+   */
+  const { setTimeout, clearTimeout } = ChromeUtils.importESModule("resource://gre/modules/Timer.sys.mjs");
+  const { XPCOMUtils } = ChromeUtils.importESModule("resource://gre/modules/XPCOMUtils.sys.mjs");
+  XPCOMUtils.defineLazyGlobalGetters(global, ["fetch", "indexedDB"]);
+  ChromeUtils.defineESModuleGetters(global, {
+      EventEmitter: "resource://gre/modules/EventEmitter.sys.mjs"
+  });
+  // Use standalone kinto-http module landed in FFx.
+  ChromeUtils.defineModuleGetter(global, "KintoHttpClient", "resource://services-common/kinto-http-client.js");
+  XPCOMUtils.defineLazyGetter(global, "generateUUID", () => {
+      const { generateUUID } = Cc["@mozilla.org/uuid-generator;1"].getService(Ci.nsIUUIDGenerator);
+      return generateUUID;
+  });
+  class Kinto extends KintoBase {
+      static get adapters() {
+          return {
+              BaseAdapter,
+              IDB,
+          };
+      }
+      get ApiClass() {
+          return KintoHttpClient;
+      }
+      constructor(options = {}) {
+          const events = {};
+          EventEmitter.decorate(events);
+          const defaults = {
+              adapter: IDB,
+              events,
+          };
+          super(Object.assign(Object.assign({}, defaults), options));
+      }
+      collection(collName, options = {}) {
+          const idSchema = {
+              validate(id) {
+                  return typeof id == "string" && RE_RECORD_ID.test(id);
+              },
+              generate() {
+                  return generateUUID()
+                      .toString()
+                      .replace(/[{}]/g, "");
+              },
+          };
+          return super.collection(collName, Object.assign({ idSchema }, options));
+      }
+  }
+
+  return Kinto;
+
+})));
diff --git a/services/common/kinto-storage-adapter.sys.mjs b/services/common/kinto-storage-adapter.sys.mjs
new file mode 100644
index 0000000000..75c6c06a26
--- /dev/null
+++ b/services/common/kinto-storage-adapter.sys.mjs
@@ -0,0 +1,553 @@
+/*
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+import { Sqlite } from "resource://gre/modules/Sqlite.sys.mjs";
+
+const { Kinto } = ChromeUtils.import(
+  "resource://services-common/kinto-offline-client.js"
+);
+
+/**
+ * Filter and sort list against provided filters and order.
+ *
+ * @param  {Object} filters  The filters to apply.
+ * @param  {String} order    The order to apply.
+ * @param  {Array}  list     The list to reduce.
+ * @return {Array}
+ */
+function reduceRecords(filters, order, list) {
+  const filtered = filters ? filterObjects(filters, list) : list;
+  return order ? sortObjects(order, filtered) : filtered;
+}
+
+/**
+ * Checks if a value is undefined.
+ *
+ * This is a copy of `_isUndefined` from kinto.js/src/utils.js.
+ * @param  {Any}  value
+ * @return {Boolean}
+ */
+function _isUndefined(value) {
+  return typeof value === "undefined";
+}
+
+/**
+ * Sorts records in a list according to a given ordering.
+ *
+ * This is a copy of `sortObjects` from kinto.js/src/utils.js.
+ *
+ * @param  {String} order The ordering, eg. `-last_modified`.
+ * @param  {Array}  list  The collection to order.
+ * @return {Array}
+ */
+function sortObjects(order, list) {
+  const hasDash = order[0] === "-";
+  const field = hasDash ? order.slice(1) : order;
+  const direction = hasDash ? -1 : 1;
+  return list.slice().sort((a, b) => {
+    if (a[field] && _isUndefined(b[field])) {
+      return direction;
+    }
+    if (b[field] && _isUndefined(a[field])) {
+      return -direction;
+    }
+    if (_isUndefined(a[field]) && _isUndefined(b[field])) {
+      return 0;
+    }
+    return a[field] > b[field] ? direction : -direction;
+  });
+}
+
+/**
+ * Test if a single object matches all given filters.
+ *
+ * This is a copy of `filterObject` from kinto.js/src/utils.js.
+ *
+ * @param  {Object} filters  The filters object.
+ * @param  {Object} entry    The object to filter.
+ * @return {Function}
+ */
+function filterObject(filters, entry) {
+  return Object.keys(filters).every(filter => {
+    const value = filters[filter];
+    if (Array.isArray(value)) {
+      return value.some(candidate => candidate === entry[filter]);
+    }
+    return entry[filter] === value;
+  });
+}
+
+/**
+ * Filters records in a list matching all given filters.
+ *
+ * This is a copy of `filterObjects` from kinto.js/src/utils.js.
+ *
+ * @param  {Object} filters  The filters object.
+ * @param  {Array}  list     The collection to filter.
+ * @return {Array}
+ */
+function filterObjects(filters, list) {
+  return list.filter(entry => {
+    return filterObject(filters, entry);
+  });
+}
+
+const statements = {
+  createCollectionData: `
+    CREATE TABLE collection_data (
+      collection_name TEXT,
+      record_id TEXT,
+      record TEXT
+    );`,
+
+  createCollectionMetadata: `
+    CREATE TABLE collection_metadata (
+      collection_name TEXT PRIMARY KEY,
+      last_modified INTEGER,
+      metadata TEXT
+    ) WITHOUT ROWID;`,
+
+  createCollectionDataRecordIdIndex: `
+    CREATE UNIQUE INDEX unique_collection_record
+      ON collection_data(collection_name, record_id);`,
+
+  clearData: `
+    DELETE FROM collection_data
+      WHERE collection_name = :collection_name;`,
+
+  createData: `
+    INSERT INTO collection_data (collection_name, record_id, record)
+      VALUES (:collection_name, :record_id, :record);`,
+
+  updateData: `
+    INSERT OR REPLACE INTO collection_data (collection_name, record_id, record)
+      VALUES (:collection_name, :record_id, :record);`,
+
+  deleteData: `
+    DELETE FROM collection_data
+      WHERE collection_name = :collection_name
+      AND record_id = :record_id;`,
+
+  saveLastModified: `
+    INSERT INTO collection_metadata(collection_name, last_modified)
+      VALUES(:collection_name, :last_modified)
+        ON CONFLICT(collection_name) DO UPDATE SET last_modified = :last_modified`,
+
+  getLastModified: `
+    SELECT last_modified
+      FROM collection_metadata
+        WHERE collection_name = :collection_name;`,
+
+  saveMetadata: `
+    INSERT INTO collection_metadata(collection_name, metadata)
+      VALUES(:collection_name, :metadata)
+        ON CONFLICT(collection_name) DO UPDATE SET metadata = :metadata`,
+
+  getMetadata: `
+    SELECT metadata
+      FROM collection_metadata
+        WHERE collection_name = :collection_name;`,
+
+  getRecord: `
+    SELECT record
+      FROM collection_data
+        WHERE collection_name = :collection_name
+        AND record_id = :record_id;`,
+
+  listRecords: `
+    SELECT record
+      FROM collection_data
+        WHERE collection_name = :collection_name;`,
+
+  // N.B. we have to have a dynamic number of placeholders, which you
+  // can't do without building your own statement. See `execute` for details
+  listRecordsById: `
+    SELECT record_id, record
+      FROM collection_data
+        WHERE collection_name = ?
+          AND record_id IN `,
+
+  importData: `
+    REPLACE INTO collection_data (collection_name, record_id, record)
+      VALUES (:collection_name, :record_id, :record);`,
+
+  scanAllRecords: `SELECT * FROM collection_data;`,
+
+  clearCollectionMetadata: `DELETE FROM collection_metadata;`,
+
+  calculateStorage: `
+    SELECT collection_name, SUM(LENGTH(record)) as size, COUNT(record) as num_records
+      FROM collection_data
+        GROUP BY collection_name;`,
+
+  addMetadataColumn: `
+    ALTER TABLE collection_metadata
+      ADD COLUMN metadata TEXT;`,
+};
+
+const createStatements = [
+  "createCollectionData",
+  "createCollectionMetadata",
+  "createCollectionDataRecordIdIndex",
+];
+
+const currentSchemaVersion = 2;
+
+/**
+ * Firefox adapter.
+ *
+ * Uses Sqlite as a backing store.
+ *
+ * Options:
+ *  - sqliteHandle: a handle to the Sqlite database this adapter will
+ *    use as its backing store. To open such a handle, use the
+ *    static openConnection() method.
+ */
+export class FirefoxAdapter extends Kinto.adapters.BaseAdapter {
+  constructor(collection, options = {}) {
+    super();
+    const { sqliteHandle = null } = options;
+    this.collection = collection;
+    this._connection = sqliteHandle;
+    this._options = options;
+  }
+
+  /**
+   * Initialize a Sqlite connection to be suitable for use with Kinto.
+   *
+   * This will be called automatically by open().
+   */
+  static async _init(connection) {
+    await connection.executeTransaction(async function doSetup() {
+      const schema = await connection.getSchemaVersion();
+
+      if (schema == 0) {
+        for (let statementName of createStatements) {
+          await connection.execute(statements[statementName]);
+        }
+        await connection.setSchemaVersion(currentSchemaVersion);
+      } else if (schema == 1) {
+        await connection.execute(statements.addMetadataColumn);
+        await connection.setSchemaVersion(currentSchemaVersion);
+      } else if (schema != 2) {
+        throw new Error("Unknown database schema: " + schema);
+      }
+    });
+    return connection;
+  }
+
+  _executeStatement(statement, params) {
+    return this._connection.executeCached(statement, params);
+  }
+
+  /**
+   * Open and initialize a Sqlite connection to a database that Kinto
+   * can use. When you are done with this connection, close it by
+   * calling close().
+   *
+   * Options:
+   *   - path: The path for the Sqlite database
+   *
+   * @returns SqliteConnection
+   */
+  static async openConnection(options) {
+    const opts = Object.assign({}, { sharedMemoryCache: false }, options);
+    const conn = await Sqlite.openConnection(opts).then(this._init);
+    try {
+      Sqlite.shutdown.addBlocker(
+        "Kinto storage adapter connection closing",
+        () => conn.close()
+      );
+    } catch (e) {
+      // It's too late to block shutdown, just close the connection.
+      await conn.close();
+      throw e;
+    }
+    return conn;
+  }
+
+  clear() {
+    const params = { collection_name: this.collection };
+    return this._executeStatement(statements.clearData, params);
+  }
+
+  execute(callback, options = { preload: [] }) {
+    let result;
+    const conn = this._connection;
+    const collection = this.collection;
+
+    return conn
+      .executeTransaction(async function doExecuteTransaction() {
+        // Preload specified records from DB, within transaction.
+
+        // if options.preload has more elements than the sqlite variable
+        // limit, split it up.
+        const limit = 100;
+        let preloaded = {};
+        let preload;
+        let more = options.preload;
+
+        while (more.length) {
+          preload = more.slice(0, limit);
+          more = more.slice(limit, more.length);
+
+          const parameters = [collection, ...preload];
+          const placeholders = preload.map(_ => "?");
+          const stmt =
+            statements.listRecordsById + "(" + placeholders.join(",") + ");";
+          const rows = await conn.execute(stmt, parameters);
+
+          rows.reduce((acc, row) => {
+            const record = JSON.parse(row.getResultByName("record"));
+            acc[row.getResultByName("record_id")] = record;
+            return acc;
+          }, preloaded);
+        }
+        const proxy = transactionProxy(collection, preloaded);
+        result = callback(proxy);
+
+        for (let { statement, params } of proxy.operations) {
+          await conn.executeCached(statement, params);
+        }
+      }, conn.TRANSACTION_EXCLUSIVE)
+      .then(_ => result);
+  }
+
+  get(id) {
+    const params = {
+      collection_name: this.collection,
+      record_id: id,
+    };
+    return this._executeStatement(statements.getRecord, params).then(result => {
+      if (!result.length) {
+        return null;
+      }
+      return JSON.parse(result[0].getResultByName("record"));
+    });
+  }
+
+  list(params = { filters: {}, order: "" }) {
+    const parameters = {
+      collection_name: this.collection,
+    };
+    return this._executeStatement(statements.listRecords, parameters)
+      .then(result => {
+        const records = [];
+        for (let k = 0; k < result.length; k++) {
+          const row = result[k];
+          records.push(JSON.parse(row.getResultByName("record")));
+        }
+        return records;
+      })
+      .then(results => {
+        // The resulting list of records is filtered and sorted.
+        // XXX: with some efforts, this could be implemented using SQL.
+        return reduceRecords(params.filters, params.order, results);
+      });
+  }
+
+  async loadDump(records) {
+    return this.importBulk(records);
+  }
+
+  /**
+   * Load a list of records into the local database.
+   *
+   * Note: The adapter is not in charge of filtering the already imported
+   * records. This is done in `Collection#loadDump()`, as a common behaviour
+   * between every adapters.
+   *
+   * @param  {Array} records.
+   * @return {Array} imported records.
+   */
+  async importBulk(records) {
+    const connection = this._connection;
+    const collection_name = this.collection;
+    await connection.executeTransaction(async function doImport() {
+      for (let record of records) {
+        const params = {
+          collection_name,
+          record_id: record.id,
+          record: JSON.stringify(record),
+        };
+        await connection.execute(statements.importData, params);
+      }
+      const lastModified = Math.max(
+        ...records.map(record => record.last_modified)
+      );
+      const params = {
+        collection_name,
+      };
+      const previousLastModified = await connection
+        .execute(statements.getLastModified, params)
+        .then(result => {
+          return result.length
+            ? result[0].getResultByName("last_modified")
+            : -1;
+        });
+      if (lastModified > previousLastModified) {
+        const params = {
+          collection_name,
+          last_modified: lastModified,
+        };
+        await connection.execute(statements.saveLastModified, params);
+      }
+    });
+    return records;
+  }
+
+  saveLastModified(lastModified) {
+    const parsedLastModified = parseInt(lastModified, 10) || null;
+    const params = {
+      collection_name: this.collection,
+      last_modified: parsedLastModified,
+    };
+    return this._executeStatement(statements.saveLastModified, params).then(
+      () => parsedLastModified
+    );
+  }
+
+  getLastModified() {
+    const params = {
+      collection_name: this.collection,
+    };
+    return this._executeStatement(statements.getLastModified, params).then(
+      result => {
+        if (!result.length) {
+          return 0;
+        }
+        return result[0].getResultByName("last_modified");
+      }
+    );
+  }
+
+  async saveMetadata(metadata) {
+    const params = {
+      collection_name: this.collection,
+      metadata: JSON.stringify(metadata),
+    };
+    await this._executeStatement(statements.saveMetadata, params);
+    return metadata;
+  }
+
+  async getMetadata() {
+    const params = {
+      collection_name: this.collection,
+    };
+    const result = await this._executeStatement(statements.getMetadata, params);
+    if (!result.length) {
+      return null;
+    }
+    return JSON.parse(result[0].getResultByName("metadata"));
+  }
+
+  calculateStorage() {
+    return this._executeStatement(statements.calculateStorage, {}).then(
+      result => {
+        return Array.from(result, row => ({
+          collectionName: row.getResultByName("collection_name"),
+          size: row.getResultByName("size"),
+          numRecords: row.getResultByName("num_records"),
+        }));
+      }
+    );
+  }
+
+  /**
+   * Reset the sync status of every record and collection we have
+   * access to.
+   */
+  resetSyncStatus() {
+    // We're going to use execute instead of executeCached, so build
+    // in our own sanity check
+    if (!this._connection) {
+      throw new Error("The storage adapter is not open");
+    }
+
+    return this._connection.executeTransaction(async function (conn) {
+      const promises = [];
+      await conn.execute(statements.scanAllRecords, null, function (row) {
+        const record = JSON.parse(row.getResultByName("record"));
+        const record_id = row.getResultByName("record_id");
+        const collection_name = row.getResultByName("collection_name");
+        if (record._status === "deleted") {
+          // Garbage collect deleted records.
+          promises.push(
+            conn.execute(statements.deleteData, { collection_name, record_id })
+          );
+        } else {
+          const newRecord = Object.assign({}, record, {
+            _status: "created",
+            last_modified: undefined,
+          });
+          promises.push(
+            conn.execute(statements.updateData, {
+              record: JSON.stringify(newRecord),
+              record_id,
+              collection_name,
+            })
+          );
+        }
+      });
+      await Promise.all(promises);
+      await conn.execute(statements.clearCollectionMetadata);
+    });
+  }
+}
+
+function transactionProxy(collection, preloaded) {
+  const _operations = [];
+
+  return {
+    get operations() {
+      return _operations;
+    },
+
+    create(record) {
+      _operations.push({
+        statement: statements.createData,
+        params: {
+          collection_name: collection,
+          record_id: record.id,
+          record: JSON.stringify(record),
+        },
+      });
+    },
+
+    update(record) {
+      _operations.push({
+        statement: statements.updateData,
+        params: {
+          collection_name: collection,
+          record_id: record.id,
+          record: JSON.stringify(record),
+        },
+      });
+    },
+
+    delete(id) {
+      _operations.push({
+        statement: statements.deleteData,
+        params: {
+          collection_name: collection,
+          record_id: id,
+        },
+      });
+    },
+
+    get(id) {
+      // Gecko JS engine outputs undesired warnings if id is not in preloaded.
+      return id in preloaded ? preloaded[id] : undefined;
+    },
+  };
+}
diff --git a/services/common/logmanager.sys.mjs b/services/common/logmanager.sys.mjs
new file mode 100644
index 0000000000..178228f3e6
--- /dev/null
+++ b/services/common/logmanager.sys.mjs
@@ -0,0 +1,449 @@
+/* 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;";
+
+import { Log } from "resource://gre/modules/Log.sys.mjs";
+
+const lazy = {};
+
+ChromeUtils.defineESModuleGetters(lazy, {
+  FileUtils: "resource://gre/modules/FileUtils.sys.mjs",
+});
+ChromeUtils.defineModuleGetter(
+  lazy,
+  "NetUtil",
+  "resource://gre/modules/NetUtil.jsm"
+);
+
+import { Preferences } from "resource://gre/modules/Preferences.sys.mjs";
+
+const DEFAULT_MAX_ERROR_AGE = 20 * 24 * 60 * 60; // 20 days
+
+// "shared" logs (ie, where the same log name is used by multiple LogManager
+// instances) are a fact of life here - eg, FirefoxAccounts logs are used by
+// both Sync and Reading List.
+// However, different instances have different pref branches, so we need to
+// handle when one pref branch says "Debug" and the other says "Error"
+// So we (a) keep singleton console and dump appenders and (b) keep track
+// of the minimum (ie, most verbose) level and use that.
+// This avoids (a) the most recent setter winning (as that is indeterminate)
+// and (b) multiple dump/console appenders being added to the same log multiple
+// times, which would cause messages to appear twice.
+
+// Singletons used by each instance.
+var formatter;
+var dumpAppender;
+var consoleAppender;
+
+// A set of all preference roots used by all instances.
+var allBranches = new Set();
+
+const STREAM_SEGMENT_SIZE = 4096;
+const PR_UINT32_MAX = 0xffffffff;
+
+/**
+ * Append to an nsIStorageStream
+ *
+ * This writes logging output to an in-memory stream which can later be read
+ * back as an nsIInputStream. It can be used to avoid expensive I/O operations
+ * during logging. Instead, one can periodically consume the input stream and
+ * e.g. write it to disk asynchronously.
+ */
+class StorageStreamAppender extends Log.Appender {
+  constructor(formatter) {
+    super(formatter);
+    this._name = "StorageStreamAppender";
+
+    this._converterStream = null; // holds the nsIConverterOutputStream
+    this._outputStream = null; // holds the underlying nsIOutputStream
+
+    this._ss = null;
+  }
+
+  get outputStream() {
+    if (!this._outputStream) {
+      // First create a raw stream. We can bail out early if that fails.
+      this._outputStream = this.newOutputStream();
+      if (!this._outputStream) {
+        return null;
+      }
+
+      // Wrap the raw stream in an nsIConverterOutputStream. We can reuse
+      // the instance if we already have one.
+      if (!this._converterStream) {
+        this._converterStream = Cc[
+          "@mozilla.org/intl/converter-output-stream;1"
+        ].createInstance(Ci.nsIConverterOutputStream);
+      }
+      this._converterStream.init(this._outputStream, "UTF-8");
+    }
+    return this._converterStream;
+  }
+
+  newOutputStream() {
+    let ss = (this._ss = Cc["@mozilla.org/storagestream;1"].createInstance(
+      Ci.nsIStorageStream
+    ));
+    ss.init(STREAM_SEGMENT_SIZE, PR_UINT32_MAX, null);
+    return ss.getOutputStream(0);
+  }
+
+  getInputStream() {
+    if (!this._ss) {
+      return null;
+    }
+    return this._ss.newInputStream(0);
+  }
+
+  reset() {
+    if (!this._outputStream) {
+      return;
+    }
+    this.outputStream.close();
+    this._outputStream = null;
+    this._ss = null;
+  }
+
+  doAppend(formatted) {
+    if (!formatted) {
+      return;
+    }
+    try {
+      this.outputStream.writeString(formatted + "\n");
+    } catch (ex) {
+      if (ex.result == Cr.NS_BASE_STREAM_CLOSED) {
+        // The underlying output stream is closed, so let's open a new one
+        // and try again.
+        this._outputStream = null;
+      }
+      try {
+        this.outputStream.writeString(formatted + "\n");
+      } catch (ex) {
+        // Ah well, we tried, but something seems to be hosed permanently.
+      }
+    }
+  }
+}
+
+// A storage appender that is flushable to a file on disk.  Policies for
+// when to flush, to what file, log rotation etc are up to the consumer
+// (although it does maintain a .sawError property to help the consumer decide
+// based on its policies)
+class FlushableStorageAppender extends StorageStreamAppender {
+  constructor(formatter) {
+    super(formatter);
+    this.sawError = false;
+  }
+
+  append(message) {
+    if (message.level >= Log.Level.Error) {
+      this.sawError = true;
+    }
+    StorageStreamAppender.prototype.append.call(this, message);
+  }
+
+  reset() {
+    super.reset();
+    this.sawError = false;
+  }
+
+  // Flush the current stream to a file. Somewhat counter-intuitively, you
+  // must pass a log which will be written to with details of the operation.
+  async flushToFile(subdirArray, filename, log) {
+    let inStream = this.getInputStream();
+    this.reset();
+    if (!inStream) {
+      log.debug("Failed to flush log to a file - no input stream");
+      return;
+    }
+    log.debug("Flushing file log");
+    log.trace("Beginning stream copy to " + filename + ": " + Date.now());
+    try {
+      await this._copyStreamToFile(inStream, subdirArray, filename, log);
+      log.trace("onCopyComplete", Date.now());
+    } catch (ex) {
+      log.error("Failed to copy log stream to file", ex);
+    }
+  }
+
+  /**
+   * Copy an input stream to the named file, doing everything off the main
+   * thread.
+   * subDirArray is an array of path components, relative to the profile
+   * directory, where the file will be created.
+   * outputFileName is the filename to create.
+   * Returns a promise that is resolved on completion or rejected with an error.
+   */
+  async _copyStreamToFile(inputStream, subdirArray, outputFileName, log) {
+    let outputDirectory = PathUtils.join(PathUtils.profileDir, ...subdirArray);
+    await IOUtils.makeDirectory(outputDirectory);
+    let fullOutputFileName = PathUtils.join(outputDirectory, outputFileName);
+
+    let outputStream = Cc[
+      "@mozilla.org/network/file-output-stream;1"
+    ].createInstance(Ci.nsIFileOutputStream);
+
+    outputStream.init(
+      new lazy.FileUtils.File(fullOutputFileName),
+      -1,
+      -1,
+      Ci.nsIFileOutputStream.DEFER_OPEN
+    );
+
+    await new Promise(resolve =>
+      lazy.NetUtil.asyncCopy(inputStream, outputStream, () => resolve())
+    );
+
+    outputStream.close();
+    log.trace("finished copy to", fullOutputFileName);
+  }
+}
+
+// The public LogManager object.
+export function LogManager(prefRoot, logNames, logFilePrefix) {
+  this._prefObservers = [];
+  this.init(prefRoot, logNames, logFilePrefix);
+}
+
+LogManager.StorageStreamAppender = StorageStreamAppender;
+
+LogManager.prototype = {
+  _cleaningUpFileLogs: false,
+
+  init(prefRoot, logNames, logFilePrefix) {
+    if (prefRoot instanceof Preferences) {
+      this._prefs = prefRoot;
+    } else {
+      this._prefs = new Preferences(prefRoot);
+    }
+
+    this.logFilePrefix = logFilePrefix;
+    if (!formatter) {
+      // Create a formatter and various appenders to attach to the logs.
+      formatter = new Log.BasicFormatter();
+      consoleAppender = new Log.ConsoleAppender(formatter);
+      dumpAppender = new Log.DumpAppender(formatter);
+    }
+
+    allBranches.add(this._prefs._branchStr);
+    // We create a preference observer for all our prefs so they are magically
+    // reflected if the pref changes after creation.
+    let setupAppender = (
+      appender,
+      prefName,
+      defaultLevel,
+      findSmallest = false
+    ) => {
+      let observer = newVal => {
+        let level = Log.Level[newVal] || defaultLevel;
+        if (findSmallest) {
+          // As some of our appenders have global impact (ie, there is only one
+          // place 'dump' goes to), we need to find the smallest value from all
+          // prefs controlling this appender.
+          // For example, if consumerA has dump=Debug then consumerB sets
+          // dump=Error, we need to keep dump=Debug so consumerA is respected.
+          for (let branch of allBranches) {
+            let lookPrefBranch = new Preferences(branch);
+            let lookVal = Log.Level[lookPrefBranch.get(prefName)];
+            if (lookVal && lookVal < level) {
+              level = lookVal;
+            }
+          }
+        }
+        appender.level = level;
+      };
+      this._prefs.observe(prefName, observer, this);
+      this._prefObservers.push([prefName, observer]);
+      // and call the observer now with the current pref value.
+      observer(this._prefs.get(prefName));
+      return observer;
+    };
+
+    this._observeConsolePref = setupAppender(
+      consoleAppender,
+      "log.appender.console",
+      Log.Level.Fatal,
+      true
+    );
+    this._observeDumpPref = setupAppender(
+      dumpAppender,
+      "log.appender.dump",
+      Log.Level.Error,
+      true
+    );
+
+    // The file appender doesn't get the special singleton behaviour.
+    let fapp = (this._fileAppender = new FlushableStorageAppender(formatter));
+    // the stream gets a default of Debug as the user must go out of their way
+    // to see the stuff spewed to it.
+    this._observeStreamPref = setupAppender(
+      fapp,
+      "log.appender.file.level",
+      Log.Level.Debug
+    );
+
+    // now attach the appenders to all our logs.
+    for (let logName of logNames) {
+      let log = Log.repository.getLogger(logName);
+      for (let appender of [fapp, dumpAppender, consoleAppender]) {
+        log.addAppender(appender);
+      }
+    }
+    // and use the first specified log as a "root" for our log.
+    this._log = Log.repository.getLogger(logNames[0] + ".LogManager");
+  },
+
+  /**
+   * Cleanup this instance
+   */
+  finalize() {
+    for (let [name, pref] of this._prefObservers) {
+      this._prefs.ignore(name, pref, this);
+    }
+    this._prefObservers = [];
+    try {
+      allBranches.delete(this._prefs._branchStr);
+    } catch (e) {}
+    this._prefs = null;
+  },
+
+  get _logFileSubDirectoryEntries() {
+    // At this point we don't allow a custom directory for the logs, nor allow
+    // it to be outside the profile directory.
+    // This returns an array of the the relative directory entries below the
+    // profile dir, and is the directory about:sync-log uses.
+    return ["weave", "logs"];
+  },
+
+  get sawError() {
+    return this._fileAppender.sawError;
+  },
+
+  // Result values for resetFileLog.
+  SUCCESS_LOG_WRITTEN: "success-log-written",
+  ERROR_LOG_WRITTEN: "error-log-written",
+
+  /**
+   * Possibly generate a log file for all accumulated log messages and refresh
+   * the input & output streams.
+   * Whether a "success" or "error" log is written is determined based on
+   * whether an "Error" log entry was written to any of the logs.
+   * Returns a promise that resolves on completion with either null (for no
+   * file written or on error), SUCCESS_LOG_WRITTEN if a "success" log was
+   * written, or ERROR_LOG_WRITTEN if an "error" log was written.
+   */
+  async resetFileLog() {
+    try {
+      let flushToFile;
+      let reasonPrefix;
+      let reason;
+      if (this._fileAppender.sawError) {
+        reason = this.ERROR_LOG_WRITTEN;
+        flushToFile = this._prefs.get("log.appender.file.logOnError", true);
+        reasonPrefix = "error";
+      } else {
+        reason = this.SUCCESS_LOG_WRITTEN;
+        flushToFile = this._prefs.get("log.appender.file.logOnSuccess", false);
+        reasonPrefix = "success";
+      }
+
+      // might as well avoid creating an input stream if we aren't going to use it.
+      if (!flushToFile) {
+        this._fileAppender.reset();
+        return null;
+      }
+
+      // We have reasonPrefix at the start of the filename so all "error"
+      // logs are grouped in about:sync-log.
+      let filename =
+        reasonPrefix + "-" + this.logFilePrefix + "-" + Date.now() + ".txt";
+      await this._fileAppender.flushToFile(
+        this._logFileSubDirectoryEntries,
+        filename,
+        this._log
+      );
+      // It's not completely clear to markh why we only do log cleanups
+      // for errors, but for now the Sync semantics have been copied...
+      // (one theory is that only cleaning up on error makes it less
+      // likely old error logs would be removed, but that's not true if
+      // there are occasional errors - let's address this later!)
+      if (reason == this.ERROR_LOG_WRITTEN && !this._cleaningUpFileLogs) {
+        this._log.trace("Running cleanup.");
+        try {
+          await this.cleanupLogs();
+        } catch (err) {
+          this._log.error("Failed to cleanup logs", err);
+        }
+      }
+      return reason;
+    } catch (ex) {
+      this._log.error("Failed to resetFileLog", ex);
+      return null;
+    }
+  },
+
+  /**
+   * Finds all logs older than maxErrorAge and deletes them using async I/O.
+   */
+  cleanupLogs() {
+    let maxAge = this._prefs.get(
+      "log.appender.file.maxErrorAge",
+      DEFAULT_MAX_ERROR_AGE
+    );
+    let threshold = Date.now() - 1000 * maxAge;
+    this._log.debug("Log cleanup threshold time: " + threshold);
+
+    let shouldDelete = fileInfo => {
+      return fileInfo.lastModified < threshold;
+    };
+    return this._deleteLogFiles(shouldDelete);
+  },
+
+  /**
+   * Finds all logs and removes them.
+   */
+  removeAllLogs() {
+    return this._deleteLogFiles(() => true);
+  },
+
+  // Delete some log files. A callback is invoked for each found log file to
+  // determine if that file should be removed.
+  async _deleteLogFiles(cbShouldDelete) {
+    this._cleaningUpFileLogs = true;
+    let logDir = lazy.FileUtils.getDir(
+      "ProfD",
+      this._logFileSubDirectoryEntries
+    );
+    for (const path of await IOUtils.getChildren(logDir.path)) {
+      const name = PathUtils.filename(path);
+
+      if (!name.startsWith("error-") && !name.startsWith("success-")) {
+        continue;
+      }
+
+      try {
+        const info = await IOUtils.stat(path);
+        if (!cbShouldDelete(info)) {
+          continue;
+        }
+
+        this._log.trace(` > Cleanup removing ${name} (${info.lastModified})`);
+        await IOUtils.remove(path);
+        this._log.trace(`Deleted ${name}`);
+      } catch (ex) {
+        this._log.debug(
+          `Encountered error trying to clean up old log file ${name}`,
+          ex
+        );
+      }
+    }
+    this._cleaningUpFileLogs = false;
+    this._log.debug("Done deleting files.");
+    // This notification is used only for tests.
+    Services.obs.notifyObservers(
+      null,
+      "services-tests:common:log-manager:cleanup-logs"
+    );
+  },
+};
diff --git a/services/common/modules-testing/logging.sys.mjs b/services/common/modules-testing/logging.sys.mjs
new file mode 100644
index 0000000000..63bd306b67
--- /dev/null
+++ b/services/common/modules-testing/logging.sys.mjs
@@ -0,0 +1,56 @@
+/* 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/. */
+
+import { Log } from "resource://gre/modules/Log.sys.mjs";
+
+export function initTestLogging(level) {
+  function LogStats() {
+    this.errorsLogged = 0;
+  }
+  LogStats.prototype = {
+    format: function format(message) {
+      if (message.level == Log.Level.Error) {
+        this.errorsLogged += 1;
+      }
+
+      return (
+        message.time +
+        "\t" +
+        message.loggerName +
+        "\t" +
+        message.levelDesc +
+        "\t" +
+        this.formatText(message) +
+        "\n"
+      );
+    },
+  };
+  Object.setPrototypeOf(LogStats.prototype, new Log.BasicFormatter());
+
+  let log = Log.repository.rootLogger;
+  let logStats = new LogStats();
+  let appender = new Log.DumpAppender(logStats);
+
+  if (typeof level == "undefined") {
+    level = "Debug";
+  }
+  getTestLogger().level = Log.Level[level];
+  Log.repository.getLogger("Services").level = Log.Level[level];
+
+  log.level = Log.Level.Trace;
+  appender.level = Log.Level.Trace;
+  // Overwrite any other appenders (e.g. from previous incarnations)
+  log.ownAppenders = [appender];
+  log.updateAppenders();
+
+  // SQLite logging is noisy in these tests - we make it quiet by default
+  // (although individual tests are free to bump it later)
+  Log.repository.getLogger("Sqlite").level = Log.Level.Info;
+
+  return logStats;
+}
+
+export function getTestLogger(component) {
+  return Log.repository.getLogger("Testing");
+}
diff --git a/services/common/moz.build b/services/common/moz.build
new file mode 100644
index 0000000000..e507b975bb
--- /dev/null
+++ b/services/common/moz.build
@@ -0,0 +1,47 @@
+# -*- 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/.
+
+with Files("**"):
+    BUG_COMPONENT = ("Cloud Services", "Firefox: Common")
+
+TEST_DIRS += ["tests"]
+
+EXPORTS.mozilla.appservices += [
+    "app_services_logger/AppServicesLoggerComponents.h",
+]
+
+EXTRA_COMPONENTS += [
+    "servicesComponents.manifest",
+]
+
+EXTRA_JS_MODULES["services-common"] += [
+    "async.sys.mjs",
+    "kinto-http-client.js",
+    "kinto-offline-client.js",
+    "kinto-storage-adapter.sys.mjs",
+    "logmanager.sys.mjs",
+    "observers.sys.mjs",
+    "rest.sys.mjs",
+    "uptake-telemetry.sys.mjs",
+    "utils.sys.mjs",
+]
+
+if CONFIG["MOZ_WIDGET_TOOLKIT"] != "android":
+    EXTRA_JS_MODULES["services-common"] += [
+        "hawkclient.sys.mjs",
+        "hawkrequest.sys.mjs",
+        "tokenserverclient.sys.mjs",
+    ]
+
+TESTING_JS_MODULES.services.common += [
+    "modules-testing/logging.sys.mjs",
+]
+
+SPHINX_TREES["/services/common"] = "docs"
+
+XPCOM_MANIFESTS += [
+    "app_services_logger/components.conf",
+]
diff --git a/services/common/observers.sys.mjs b/services/common/observers.sys.mjs
new file mode 100644
index 0000000000..c79b2b1bf2
--- /dev/null
+++ b/services/common/observers.sys.mjs
@@ -0,0 +1,148 @@
+/* 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/. */
+
+/**
+ * A service for adding, removing and notifying observers of notifications.
+ * Wraps the nsIObserverService interface.
+ *
+ * @version 0.2
+ */
+export var Observers = {
+  /**
+   * Register the given callback as an observer of the given topic.
+   *
+   * @param   topic       {String}
+   *          the topic to observe
+   *
+   * @param   callback    {Object}
+   *          the callback; an Object that implements nsIObserver or a Function
+   *          that gets called when the notification occurs
+   *
+   * @param   thisObject  {Object}  [optional]
+   *          the object to use as |this| when calling a Function callback
+   *
+   * @returns the observer
+   */
+  add(topic, callback, thisObject) {
+    let observer = new Observer(topic, callback, thisObject);
+    this._cache.push(observer);
+    Services.obs.addObserver(observer, topic, true);
+
+    return observer;
+  },
+
+  /**
+   * Unregister the given callback as an observer of the given topic.
+   *
+   * @param topic       {String}
+   *        the topic being observed
+   *
+   * @param callback    {Object}
+   *        the callback doing the observing
+   *
+   * @param thisObject  {Object}  [optional]
+   *        the object being used as |this| when calling a Function callback
+   */
+  remove(topic, callback, thisObject) {
+    // This seems fairly inefficient, but I'm not sure how much better
+    // we can make it.  We could index by topic, but we can't index by callback
+    // or thisObject, as far as I know, since the keys to JavaScript hashes
+    // (a.k.a. objects) can apparently only be primitive values.
+    let [observer] = this._cache.filter(
+      v =>
+        v.topic == topic && v.callback == callback && v.thisObject == thisObject
+    );
+    if (observer) {
+      Services.obs.removeObserver(observer, topic);
+      this._cache.splice(this._cache.indexOf(observer), 1);
+    } else {
+      throw new Error("Attempt to remove non-existing observer");
+    }
+  },
+
+  /**
+   * Notify observers about something.
+   *
+   * @param topic   {String}
+   *        the topic to notify observers about
+   *
+   * @param subject {Object}  [optional]
+   *        some information about the topic; can be any JS object or primitive
+   *
+   * @param data    {String}  [optional] [deprecated]
+   *        some more information about the topic; deprecated as the subject
+   *        is sufficient to pass all needed information to the JS observers
+   *        that this module targets; if you have multiple values to pass to
+   *        the observer, wrap them in an object and pass them via the subject
+   *        parameter (i.e.: { foo: 1, bar: "some string", baz: myObject })
+   */
+  notify(topic, subject, data) {
+    subject = typeof subject == "undefined" ? null : new Subject(subject);
+    data = typeof data == "undefined" ? null : data;
+    Services.obs.notifyObservers(subject, topic, data);
+  },
+
+  /**
+   * A cache of observers that have been added.
+   *
+   * We use this to remove observers when a caller calls |remove|.
+   *
+   * XXX This might result in reference cycles, causing memory leaks,
+   * if we hold a reference to an observer that holds a reference to us.
+   * Could we fix that by making this an independent top-level object
+   * rather than a property of this object?
+   */
+  _cache: [],
+};
+
+function Observer(topic, callback, thisObject) {
+  this.topic = topic;
+  this.callback = callback;
+  this.thisObject = thisObject;
+}
+
+Observer.prototype = {
+  QueryInterface: ChromeUtils.generateQI([
+    "nsIObserver",
+    "nsISupportsWeakReference",
+  ]),
+  observe(subject, topic, data) {
+    // Extract the wrapped object for subjects that are one of our wrappers
+    // around a JS object.  This way we support both wrapped subjects created
+    // using this module and those that are real XPCOM components.
+    if (
+      subject &&
+      typeof subject == "object" &&
+      "wrappedJSObject" in subject &&
+      "observersModuleSubjectWrapper" in subject.wrappedJSObject
+    ) {
+      subject = subject.wrappedJSObject.object;
+    }
+
+    if (typeof this.callback == "function") {
+      if (this.thisObject) {
+        this.callback.call(this.thisObject, subject, data);
+      } else {
+        this.callback(subject, data);
+      }
+    } else {
+      // typeof this.callback == "object" (nsIObserver)
+      this.callback.observe(subject, topic, data);
+    }
+  },
+};
+
+function Subject(object) {
+  // Double-wrap the object and set a property identifying the wrappedJSObject
+  // as one of our wrappers to distinguish between subjects that are one of our
+  // wrappers (which we should unwrap when notifying our observers) and those
+  // that are real JS XPCOM components (which we should pass through unaltered).
+  this.wrappedJSObject = { observersModuleSubjectWrapper: true, object };
+}
+
+Subject.prototype = {
+  QueryInterface: ChromeUtils.generateQI([]),
+  getScriptableHelper() {},
+  getInterfaces() {},
+};
diff --git a/services/common/rest.sys.mjs b/services/common/rest.sys.mjs
new file mode 100644
index 0000000000..a6f9424211
--- /dev/null
+++ b/services/common/rest.sys.mjs
@@ -0,0 +1,720 @@
+/* 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/. */
+
+const { NetUtil } = ChromeUtils.import("resource://gre/modules/NetUtil.jsm");
+import { Log } from "resource://gre/modules/Log.sys.mjs";
+import { PromiseUtils } from "resource://gre/modules/PromiseUtils.sys.mjs";
+
+import { CommonUtils } from "resource://services-common/utils.sys.mjs";
+
+const lazy = {};
+
+ChromeUtils.defineESModuleGetters(lazy, {
+  CryptoUtils: "resource://services-crypto/utils.sys.mjs",
+});
+
+function decodeString(data, charset) {
+  if (!data || !charset) {
+    return data;
+  }
+
+  // This could be simpler if we assumed the charset is only ever UTF-8.
+  // It's unclear to me how willing we are to assume this, though...
+  let stringStream = Cc["@mozilla.org/io/string-input-stream;1"].createInstance(
+    Ci.nsIStringInputStream
+  );
+  stringStream.setData(data, data.length);
+
+  let converterStream = Cc[
+    "@mozilla.org/intl/converter-input-stream;1"
+  ].createInstance(Ci.nsIConverterInputStream);
+
+  converterStream.init(
+    stringStream,
+    charset,
+    0,
+    converterStream.DEFAULT_REPLACEMENT_CHARACTER
+  );
+
+  let remaining = data.length;
+  let body = "";
+  while (remaining > 0) {
+    let str = {};
+    let num = converterStream.readString(remaining, str);
+    if (!num) {
+      break;
+    }
+    remaining -= num;
+    body += str.value;
+  }
+  return body;
+}
+
+/**
+ * Single use HTTP requests to RESTish resources.
+ *
+ * @param uri
+ *        URI for the request. This can be an nsIURI object or a string
+ *        that can be used to create one. An exception will be thrown if
+ *        the string is not a valid URI.
+ *
+ * Examples:
+ *
+ * (1) Quick GET request:
+ *
+ *   let response = await new RESTRequest("http://server/rest/resource").get();
+ *   if (!response.success) {
+ *     // Bail out if we're not getting an HTTP 2xx code.
+ *     processHTTPError(response.status);
+ *     return;
+ *   }
+ *   processData(response.body);
+ *
+ * (2) Quick PUT request (non-string data is automatically JSONified)
+ *
+ *   let response = await new RESTRequest("http://server/rest/resource").put(data);
+ */
+export function RESTRequest(uri) {
+  this.status = this.NOT_SENT;
+
+  // If we don't have an nsIURI object yet, make one. This will throw if
+  // 'uri' isn't a valid URI string.
+  if (!(uri instanceof Ci.nsIURI)) {
+    uri = Services.io.newURI(uri);
+  }
+  this.uri = uri;
+
+  this._headers = {};
+  this._deferred = PromiseUtils.defer();
+  this._log = Log.repository.getLogger(this._logName);
+  this._log.manageLevelFromPref("services.common.log.logger.rest.request");
+}
+
+RESTRequest.prototype = {
+  _logName: "Services.Common.RESTRequest",
+
+  QueryInterface: ChromeUtils.generateQI([
+    "nsIInterfaceRequestor",
+    "nsIChannelEventSink",
+  ]),
+
+  /** Public API: **/
+
+  /**
+   * URI for the request (an nsIURI object).
+   */
+  uri: null,
+
+  /**
+   * HTTP method (e.g. "GET")
+   */
+  method: null,
+
+  /**
+   * RESTResponse object
+   */
+  response: null,
+
+  /**
+   * nsIRequest load flags. Don't do any caching by default. Don't send user
+   * cookies and such over the wire (Bug 644734).
+   */
+  loadFlags:
+    Ci.nsIRequest.LOAD_BYPASS_CACHE |
+    Ci.nsIRequest.INHIBIT_CACHING |
+    Ci.nsIRequest.LOAD_ANONYMOUS,
+
+  /**
+   * nsIHttpChannel
+   */
+  channel: null,
+
+  /**
+   * Flag to indicate the status of the request.
+   *
+   * One of NOT_SENT, SENT, IN_PROGRESS, COMPLETED, ABORTED.
+   */
+  status: null,
+
+  NOT_SENT: 0,
+  SENT: 1,
+  IN_PROGRESS: 2,
+  COMPLETED: 4,
+  ABORTED: 8,
+
+  /**
+   * HTTP status text of response
+   */
+  statusText: null,
+
+  /**
+   * Request timeout (in seconds, though decimal values can be used for
+   * up to millisecond granularity.)
+   *
+   * 0 for no timeout. Default is 300 seconds (5 minutes), the same as Sync uses
+   * in resource.js.
+   */
+  timeout: 300,
+
+  /**
+   * The encoding with which the response to this request must be treated.
+   * If a charset parameter is available in the HTTP Content-Type header for
+   * this response, that will always be used, and this value is ignored. We
+   * default to UTF-8 because that is a reasonable default.
+   */
+  charset: "utf-8",
+
+  /**
+   * Set a request header.
+   */
+  setHeader(name, value) {
+    this._headers[name.toLowerCase()] = value;
+  },
+
+  /**
+   * Perform an HTTP GET.
+   *
+   * @return Promise<RESTResponse>
+   */
+  async get() {
+    return this.dispatch("GET", null);
+  },
+
+  /**
+   * Perform an HTTP PATCH.
+   *
+   * @param data
+   *        Data to be used as the request body. If this isn't a string
+   *        it will be JSONified automatically.
+   *
+   * @return Promise<RESTResponse>
+   */
+  async patch(data) {
+    return this.dispatch("PATCH", data);
+  },
+
+  /**
+   * Perform an HTTP PUT.
+   *
+   * @param data
+   *        Data to be used as the request body. If this isn't a string
+   *        it will be JSONified automatically.
+   *
+   * @return Promise<RESTResponse>
+   */
+  async put(data) {
+    return this.dispatch("PUT", data);
+  },
+
+  /**
+   * Perform an HTTP POST.
+   *
+   * @param data
+   *        Data to be used as the request body. If this isn't a string
+   *        it will be JSONified automatically.
+   *
+   * @return Promise<RESTResponse>
+   */
+  async post(data) {
+    return this.dispatch("POST", data);
+  },
+
+  /**
+   * Perform an HTTP DELETE.
+   *
+   * @return Promise<RESTResponse>
+   */
+  async delete() {
+    return this.dispatch("DELETE", null);
+  },
+
+  /**
+   * Abort an active request.
+   */
+  abort(rejectWithError = null) {
+    if (this.status != this.SENT && this.status != this.IN_PROGRESS) {
+      throw new Error("Can only abort a request that has been sent.");
+    }
+
+    this.status = this.ABORTED;
+    this.channel.cancel(Cr.NS_BINDING_ABORTED);
+
+    if (this.timeoutTimer) {
+      // Clear the abort timer now that the channel is done.
+      this.timeoutTimer.clear();
+    }
+    if (rejectWithError) {
+      this._deferred.reject(rejectWithError);
+    }
+  },
+
+  /** Implementation stuff **/
+
+  async dispatch(method, data) {
+    if (this.status != this.NOT_SENT) {
+      throw new Error("Request has already been sent!");
+    }
+
+    this.method = method;
+
+    // Create and initialize HTTP channel.
+    let channel = NetUtil.newChannel({
+      uri: this.uri,
+      loadUsingSystemPrincipal: true,
+    })
+      .QueryInterface(Ci.nsIRequest)
+      .QueryInterface(Ci.nsIHttpChannel);
+    this.channel = channel;
+    channel.loadFlags |= this.loadFlags;
+    channel.notificationCallbacks = this;
+
+    this._log.debug(`${method} request to ${this.uri.spec}`);
+    // Set request headers.
+    let headers = this._headers;
+    for (let key in headers) {
+      if (key == "authorization" || key == "x-client-state") {
+        this._log.trace("HTTP Header " + key + ": ***** (suppressed)");
+      } else {
+        this._log.trace("HTTP Header " + key + ": " + headers[key]);
+      }
+      channel.setRequestHeader(key, headers[key], false);
+    }
+
+    // REST requests accept JSON by default
+    if (!headers.accept) {
+      channel.setRequestHeader(
+        "accept",
+        "application/json;q=0.9,*/*;q=0.2",
+        false
+      );
+    }
+
+    // Set HTTP request body.
+    if (method == "PUT" || method == "POST" || method == "PATCH") {
+      // Convert non-string bodies into JSON with utf-8 encoding. If a string
+      // is passed we assume they've already encoded it.
+      let contentType = headers["content-type"];
+      if (typeof data != "string") {
+        data = JSON.stringify(data);
+        if (!contentType) {
+          contentType = "application/json";
+        }
+        if (!contentType.includes("charset")) {
+          data = CommonUtils.encodeUTF8(data);
+          contentType += "; charset=utf-8";
+        } else {
+          // If someone handed us an object but also a custom content-type
+          // it's probably confused. We could go to even further lengths to
+          // respect it, but this shouldn't happen in practice.
+          console.error(
+            "rest.js found an object to JSON.stringify but also a " +
+              "content-type header with a charset specification. " +
+              "This probably isn't going to do what you expect"
+          );
+        }
+      }
+      if (!contentType) {
+        contentType = "text/plain";
+      }
+
+      this._log.debug(method + " Length: " + data.length);
+      if (this._log.level <= Log.Level.Trace) {
+        this._log.trace(method + " Body: " + data);
+      }
+
+      let stream = Cc["@mozilla.org/io/string-input-stream;1"].createInstance(
+        Ci.nsIStringInputStream
+      );
+      stream.setData(data, data.length);
+
+      channel.QueryInterface(Ci.nsIUploadChannel);
+      channel.setUploadStream(stream, contentType, data.length);
+    }
+    // We must set this after setting the upload stream, otherwise it
+    // will always be 'PUT'. Yeah, I know.
+    channel.requestMethod = method;
+
+    // Before opening the channel, set the charset that serves as a hint
+    // as to what the response might be encoded as.
+    channel.contentCharset = this.charset;
+
+    // Blast off!
+    try {
+      channel.asyncOpen(this);
+    } catch (ex) {
+      // asyncOpen can throw in a bunch of cases -- e.g., a forbidden port.
+      this._log.warn("Caught an error in asyncOpen", ex);
+      this._deferred.reject(ex);
+    }
+    this.status = this.SENT;
+    this.delayTimeout();
+    return this._deferred.promise;
+  },
+
+  /**
+   * Create or push back the abort timer that kills this request.
+   */
+  delayTimeout() {
+    if (this.timeout) {
+      CommonUtils.namedTimer(
+        this.abortTimeout,
+        this.timeout * 1000,
+        this,
+        "timeoutTimer"
+      );
+    }
+  },
+
+  /**
+   * Abort the request based on a timeout.
+   */
+  abortTimeout() {
+    this.abort(
+      Components.Exception(
+        "Aborting due to channel inactivity.",
+        Cr.NS_ERROR_NET_TIMEOUT
+      )
+    );
+  },
+
+  /** nsIStreamListener **/
+
+  onStartRequest(channel) {
+    if (this.status == this.ABORTED) {
+      this._log.trace(
+        "Not proceeding with onStartRequest, request was aborted."
+      );
+      // We might have already rejected, but just in case.
+      this._deferred.reject(
+        Components.Exception("Request aborted", Cr.NS_BINDING_ABORTED)
+      );
+      return;
+    }
+
+    try {
+      channel.QueryInterface(Ci.nsIHttpChannel);
+    } catch (ex) {
+      this._log.error("Unexpected error: channel is not a nsIHttpChannel!");
+      this.status = this.ABORTED;
+      channel.cancel(Cr.NS_BINDING_ABORTED);
+      this._deferred.reject(ex);
+      return;
+    }
+
+    this.status = this.IN_PROGRESS;
+
+    this._log.trace(
+      "onStartRequest: " + channel.requestMethod + " " + channel.URI.spec
+    );
+
+    // Create a new response object.
+    this.response = new RESTResponse(this);
+
+    this.delayTimeout();
+  },
+
+  onStopRequest(channel, statusCode) {
+    if (this.timeoutTimer) {
+      // Clear the abort timer now that the channel is done.
+      this.timeoutTimer.clear();
+    }
+
+    // We don't want to do anything for a request that's already been aborted.
+    if (this.status == this.ABORTED) {
+      this._log.trace(
+        "Not proceeding with onStopRequest, request was aborted."
+      );
+      // We might not have already rejected if the user called reject() manually.
+      // If we have already rejected, then this is a no-op
+      this._deferred.reject(
+        Components.Exception("Request aborted", Cr.NS_BINDING_ABORTED)
+      );
+      return;
+    }
+
+    try {
+      channel.QueryInterface(Ci.nsIHttpChannel);
+    } catch (ex) {
+      this._log.error("Unexpected error: channel not nsIHttpChannel!");
+      this.status = this.ABORTED;
+      this._deferred.reject(ex);
+      return;
+    }
+
+    this.status = this.COMPLETED;
+
+    try {
+      this.response.body = decodeString(
+        this.response._rawBody,
+        this.response.charset
+      );
+      this.response._rawBody = null;
+    } catch (ex) {
+      this._log.warn(
+        `Exception decoding response - ${this.method} ${channel.URI.spec}`,
+        ex
+      );
+      this._deferred.reject(ex);
+      return;
+    }
+
+    let statusSuccess = Components.isSuccessCode(statusCode);
+    let uri = (channel && channel.URI && channel.URI.spec) || "<unknown>";
+    this._log.trace(
+      "Channel for " +
+        channel.requestMethod +
+        " " +
+        uri +
+        " returned status code " +
+        statusCode
+    );
+
+    // Throw the failure code and stop execution.  Use Components.Exception()
+    // instead of Error() so the exception is QI-able and can be passed across
+    // XPCOM borders while preserving the status code.
+    if (!statusSuccess) {
+      let message = Components.Exception("", statusCode).name;
+      let error = Components.Exception(message, statusCode);
+      this._log.debug(
+        this.method + " " + uri + " failed: " + statusCode + " - " + message
+      );
+      // Additionally give the full response body when Trace logging.
+      if (this._log.level <= Log.Level.Trace) {
+        this._log.trace(this.method + " body", this.response.body);
+      }
+      this._deferred.reject(error);
+      return;
+    }
+
+    this._log.debug(this.method + " " + uri + " " + this.response.status);
+
+    // Note that for privacy/security reasons we don't log this response body
+
+    delete this._inputStream;
+
+    this._deferred.resolve(this.response);
+  },
+
+  onDataAvailable(channel, stream, off, count) {
+    // We get an nsIRequest, which doesn't have contentCharset.
+    try {
+      channel.QueryInterface(Ci.nsIHttpChannel);
+    } catch (ex) {
+      this._log.error("Unexpected error: channel not nsIHttpChannel!");
+      this.abort(ex);
+      return;
+    }
+
+    if (channel.contentCharset) {
+      this.response.charset = channel.contentCharset;
+    } else {
+      this.response.charset = null;
+    }
+
+    if (!this._inputStream) {
+      this._inputStream = Cc[
+        "@mozilla.org/scriptableinputstream;1"
+      ].createInstance(Ci.nsIScriptableInputStream);
+    }
+    this._inputStream.init(stream);
+
+    this.response._rawBody += this._inputStream.read(count);
+
+    this.delayTimeout();
+  },
+
+  /** nsIInterfaceRequestor **/
+
+  getInterface(aIID) {
+    return this.QueryInterface(aIID);
+  },
+
+  /**
+   * Returns true if headers from the old channel should be
+   * copied to the new channel. Invoked when a channel redirect
+   * is in progress.
+   */
+  shouldCopyOnRedirect(oldChannel, newChannel, flags) {
+    let isInternal = !!(flags & Ci.nsIChannelEventSink.REDIRECT_INTERNAL);
+    let isSameURI = newChannel.URI.equals(oldChannel.URI);
+    this._log.debug(
+      "Channel redirect: " +
+        oldChannel.URI.spec +
+        ", " +
+        newChannel.URI.spec +
+        ", internal = " +
+        isInternal
+    );
+    return isInternal && isSameURI;
+  },
+
+  /** nsIChannelEventSink **/
+  asyncOnChannelRedirect(oldChannel, newChannel, flags, callback) {
+    let oldSpec =
+      oldChannel && oldChannel.URI ? oldChannel.URI.spec : "<undefined>";
+    let newSpec =
+      newChannel && newChannel.URI ? newChannel.URI.spec : "<undefined>";
+    this._log.debug(
+      "Channel redirect: " + oldSpec + ", " + newSpec + ", " + flags
+    );
+
+    try {
+      newChannel.QueryInterface(Ci.nsIHttpChannel);
+    } catch (ex) {
+      this._log.error("Unexpected error: channel not nsIHttpChannel!");
+      callback.onRedirectVerifyCallback(Cr.NS_ERROR_NO_INTERFACE);
+      return;
+    }
+
+    // For internal redirects, copy the headers that our caller set.
+    try {
+      if (this.shouldCopyOnRedirect(oldChannel, newChannel, flags)) {
+        this._log.trace("Copying headers for safe internal redirect.");
+        for (let key in this._headers) {
+          newChannel.setRequestHeader(key, this._headers[key], false);
+        }
+      }
+    } catch (ex) {
+      this._log.error("Error copying headers", ex);
+    }
+
+    this.channel = newChannel;
+
+    // We let all redirects proceed.
+    callback.onRedirectVerifyCallback(Cr.NS_OK);
+  },
+};
+
+/**
+ * Response object for a RESTRequest. This will be created automatically by
+ * the RESTRequest.
+ */
+export function RESTResponse(request = null) {
+  this.body = "";
+  this._rawBody = "";
+  this.request = request;
+  this._log = Log.repository.getLogger(this._logName);
+  this._log.manageLevelFromPref("services.common.log.logger.rest.response");
+}
+
+RESTResponse.prototype = {
+  _logName: "Services.Common.RESTResponse",
+
+  /**
+   * Corresponding REST request
+   */
+  request: null,
+
+  /**
+   * HTTP status code
+   */
+  get status() {
+    let status;
+    try {
+      status = this.request.channel.responseStatus;
+    } catch (ex) {
+      this._log.debug("Caught exception fetching HTTP status code", ex);
+      return null;
+    }
+    Object.defineProperty(this, "status", { value: status });
+    return status;
+  },
+
+  /**
+   * HTTP status text
+   */
+  get statusText() {
+    let statusText;
+    try {
+      statusText = this.request.channel.responseStatusText;
+    } catch (ex) {
+      this._log.debug("Caught exception fetching HTTP status text", ex);
+      return null;
+    }
+    Object.defineProperty(this, "statusText", { value: statusText });
+    return statusText;
+  },
+
+  /**
+   * Boolean flag that indicates whether the HTTP status code is 2xx or not.
+   */
+  get success() {
+    let success;
+    try {
+      success = this.request.channel.requestSucceeded;
+    } catch (ex) {
+      this._log.debug("Caught exception fetching HTTP success flag", ex);
+      return null;
+    }
+    Object.defineProperty(this, "success", { value: success });
+    return success;
+  },
+
+  /**
+   * Object containing HTTP headers (keyed as lower case)
+   */
+  get headers() {
+    let headers = {};
+    try {
+      this._log.trace("Processing response headers.");
+      let channel = this.request.channel.QueryInterface(Ci.nsIHttpChannel);
+      channel.visitResponseHeaders(function (header, value) {
+        headers[header.toLowerCase()] = value;
+      });
+    } catch (ex) {
+      this._log.debug("Caught exception processing response headers", ex);
+      return null;
+    }
+
+    Object.defineProperty(this, "headers", { value: headers });
+    return headers;
+  },
+
+  /**
+   * HTTP body (string)
+   */
+  body: null,
+};
+
+/**
+ * Single use MAC authenticated HTTP requests to RESTish resources.
+ *
+ * @param uri
+ *        URI going to the RESTRequest constructor.
+ * @param authToken
+ *        (Object) An auth token of the form {id: (string), key: (string)}
+ *        from which the MAC Authentication header for this request will be
+ *        derived. A token as obtained from
+ *        TokenServerClient.getTokenUsingOAuth is accepted.
+ * @param extra
+ *        (Object) Optional extra parameters. Valid keys are: nonce_bytes, ts,
+ *        nonce, and ext. See CrytoUtils.computeHTTPMACSHA1 for information on
+ *        the purpose of these values.
+ */
+export function TokenAuthenticatedRESTRequest(uri, authToken, extra) {
+  RESTRequest.call(this, uri);
+  this.authToken = authToken;
+  this.extra = extra || {};
+}
+
+TokenAuthenticatedRESTRequest.prototype = {
+  async dispatch(method, data) {
+    let sig = await lazy.CryptoUtils.computeHTTPMACSHA1(
+      this.authToken.id,
+      this.authToken.key,
+      method,
+      this.uri,
+      this.extra
+    );
+
+    this.setHeader("Authorization", sig.getHeader());
+
+    return super.dispatch(method, data);
+  },
+};
+
+Object.setPrototypeOf(
+  TokenAuthenticatedRESTRequest.prototype,
+  RESTRequest.prototype
+);
diff --git a/services/common/servicesComponents.manifest b/services/common/servicesComponents.manifest
new file mode 100644
index 0000000000..fe2a52fab6
--- /dev/null
+++ b/services/common/servicesComponents.manifest
@@ -0,0 +1,2 @@
+# Register resource aliases
+resource services-common resource://gre/modules/services-common/
diff --git a/services/common/tests/moz.build b/services/common/tests/moz.build
new file mode 100644
index 0000000000..edf7213b91
--- /dev/null
+++ b/services/common/tests/moz.build
@@ -0,0 +1,9 @@
+# -*- 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/.
+
+XPCSHELL_TESTS_MANIFESTS += ["unit/xpcshell.ini"]
+
+TEST_DIRS += ["unit"]
diff --git a/services/common/tests/unit/head_global.js b/services/common/tests/unit/head_global.js
new file mode 100644
index 0000000000..bcb1c063a4
--- /dev/null
+++ b/services/common/tests/unit/head_global.js
@@ -0,0 +1,35 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+var Cm = Components.manager;
+
+// Required to avoid failures.
+do_get_profile();
+var { XPCOMUtils } = ChromeUtils.importESModule(
+  "resource://gre/modules/XPCOMUtils.sys.mjs"
+);
+
+const { updateAppInfo } = ChromeUtils.importESModule(
+  "resource://testing-common/AppInfo.sys.mjs"
+);
+updateAppInfo({
+  name: "XPCShell",
+  ID: "xpcshell@tests.mozilla.org",
+  version: "1",
+  platformVersion: "",
+});
+
+function addResourceAlias() {
+  const handler = Services.io
+    .getProtocolHandler("resource")
+    .QueryInterface(Ci.nsIResProtocolHandler);
+
+  let modules = ["common", "crypto", "settings"];
+  for (let module of modules) {
+    let uri = Services.io.newURI(
+      "resource://gre/modules/services-" + module + "/"
+    );
+    handler.setSubstitution("services-" + module, uri);
+  }
+}
+addResourceAlias();
diff --git a/services/common/tests/unit/head_helpers.js b/services/common/tests/unit/head_helpers.js
new file mode 100644
index 0000000000..1947ece254
--- /dev/null
+++ b/services/common/tests/unit/head_helpers.js
@@ -0,0 +1,268 @@
+/* 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/. */
+
+/* import-globals-from head_global.js */
+
+var { Log } = ChromeUtils.importESModule("resource://gre/modules/Log.sys.mjs");
+var { CommonUtils } = ChromeUtils.importESModule(
+  "resource://services-common/utils.sys.mjs"
+);
+var {
+  HTTP_400,
+  HTTP_401,
+  HTTP_402,
+  HTTP_403,
+  HTTP_404,
+  HTTP_405,
+  HTTP_406,
+  HTTP_407,
+  HTTP_408,
+  HTTP_409,
+  HTTP_410,
+  HTTP_411,
+  HTTP_412,
+  HTTP_413,
+  HTTP_414,
+  HTTP_415,
+  HTTP_417,
+  HTTP_500,
+  HTTP_501,
+  HTTP_502,
+  HTTP_503,
+  HTTP_504,
+  HTTP_505,
+  HttpError,
+  HttpServer,
+} = ChromeUtils.import("resource://testing-common/httpd.js");
+var { getTestLogger, initTestLogging } = ChromeUtils.importESModule(
+  "resource://testing-common/services/common/logging.sys.mjs"
+);
+var { MockRegistrar } = ChromeUtils.importESModule(
+  "resource://testing-common/MockRegistrar.sys.mjs"
+);
+var { NetUtil } = ChromeUtils.import("resource://gre/modules/NetUtil.jsm");
+
+function do_check_empty(obj) {
+  do_check_attribute_count(obj, 0);
+}
+
+function do_check_attribute_count(obj, c) {
+  Assert.equal(c, Object.keys(obj).length);
+}
+
+function do_check_throws(aFunc, aResult) {
+  try {
+    aFunc();
+  } catch (e) {
+    Assert.equal(e.result, aResult);
+    return;
+  }
+  do_throw("Expected result " + aResult + ", none thrown.");
+}
+
+/**
+ * Test whether specified function throws exception with expected
+ * result.
+ *
+ * @param func
+ *        Function to be tested.
+ * @param message
+ *        Message of expected exception. <code>null</code> for no throws.
+ */
+function do_check_throws_message(aFunc, aResult) {
+  try {
+    aFunc();
+  } catch (e) {
+    Assert.equal(e.message, aResult);
+    return;
+  }
+  do_throw("Expected an error, none thrown.");
+}
+
+/**
+ * Print some debug message to the console. All arguments will be printed,
+ * separated by spaces.
+ *
+ * @param [arg0, arg1, arg2, ...]
+ *        Any number of arguments to print out
+ * @usage _("Hello World") -> prints "Hello World"
+ * @usage _(1, 2, 3) -> prints "1 2 3"
+ */
+var _ = function (some, debug, text, to) {
+  print(Array.from(arguments).join(" "));
+};
+
+function httpd_setup(handlers, port = -1) {
+  let server = new HttpServer();
+  for (let path in handlers) {
+    server.registerPathHandler(path, handlers[path]);
+  }
+  try {
+    server.start(port);
+  } catch (ex) {
+    _("==========================================");
+    _("Got exception starting HTTP server on port " + port);
+    _("Error: " + Log.exceptionStr(ex));
+    _("Is there a process already listening on port " + port + "?");
+    _("==========================================");
+    do_throw(ex);
+  }
+
+  // Set the base URI for convenience.
+  let i = server.identity;
+  server.baseURI =
+    i.primaryScheme + "://" + i.primaryHost + ":" + i.primaryPort;
+
+  return server;
+}
+
+function httpd_handler(statusCode, status, body) {
+  return function handler(request, response) {
+    _("Processing request");
+    // Allow test functions to inspect the request.
+    request.body = readBytesFromInputStream(request.bodyInputStream);
+    handler.request = request;
+
+    response.setStatusLine(request.httpVersion, statusCode, status);
+    if (body) {
+      response.bodyOutputStream.write(body, body.length);
+    }
+  };
+}
+
+function promiseStopServer(server) {
+  return new Promise(resolve => server.stop(resolve));
+}
+
+/*
+ * Read bytes string from an nsIInputStream.  If 'count' is omitted,
+ * all available input is read.
+ */
+function readBytesFromInputStream(inputStream, count) {
+  if (!count) {
+    count = inputStream.available();
+  }
+  if (!count) {
+    return "";
+  }
+  return NetUtil.readInputStreamToString(inputStream, count, {
+    charset: "UTF-8",
+  });
+}
+
+function writeBytesToOutputStream(outputStream, string) {
+  if (!string) {
+    return;
+  }
+  let converter = Cc[
+    "@mozilla.org/intl/converter-output-stream;1"
+  ].createInstance(Ci.nsIConverterOutputStream);
+  converter.init(outputStream, "UTF-8");
+  converter.writeString(string);
+  converter.close();
+}
+
+/*
+ * Ensure exceptions from inside callbacks leads to test failures.
+ */
+function ensureThrows(func) {
+  return function () {
+    try {
+      func.apply(this, arguments);
+    } catch (ex) {
+      do_throw(ex);
+    }
+  };
+}
+
+/**
+ * Proxy auth helpers.
+ */
+
+/**
+ * Fake a PAC to prompt a channel replacement.
+ */
+var PACSystemSettings = {
+  QueryInterface: ChromeUtils.generateQI(["nsISystemProxySettings"]),
+
+  // Replace this URI for each test to avoid caching. We want to ensure that
+  // each test gets a completely fresh setup.
+  mainThreadOnly: true,
+  PACURI: null,
+  getProxyForURI: function getProxyForURI(aURI) {
+    throw Components.Exception("", Cr.NS_ERROR_NOT_IMPLEMENTED);
+  },
+};
+
+var fakePACCID;
+function installFakePAC() {
+  _("Installing fake PAC.");
+  fakePACCID = MockRegistrar.register(
+    "@mozilla.org/system-proxy-settings;1",
+    PACSystemSettings
+  );
+}
+
+function uninstallFakePAC() {
+  _("Uninstalling fake PAC.");
+  MockRegistrar.unregister(fakePACCID);
+}
+
+function getUptakeTelemetrySnapshot(component, source) {
+  const TELEMETRY_CATEGORY_ID = "uptake.remotecontent.result";
+  const snapshot = Services.telemetry.snapshotEvents(
+    Ci.nsITelemetry.DATASET_ALL_CHANNELS,
+    true
+  );
+  const parentEvents = snapshot.parent || [];
+  return (
+    parentEvents
+      // Transform raw event data to objects.
+      .map(([i, category, method, object, value, extras]) => {
+        return { category, method, object, value, extras };
+      })
+      // Keep only for the specified component and source.
+      .filter(
+        e =>
+          e.category == TELEMETRY_CATEGORY_ID &&
+          e.object == component &&
+          e.extras.source == source
+      )
+      // Return total number of events received by status, to mimic histograms snapshots.
+      .reduce((acc, e) => {
+        acc[e.value] = (acc[e.value] || 0) + 1;
+        return acc;
+      }, {})
+  );
+}
+
+function checkUptakeTelemetry(snapshot1, snapshot2, expectedIncrements) {
+  const { UptakeTelemetry } = ChromeUtils.importESModule(
+    "resource://services-common/uptake-telemetry.sys.mjs"
+  );
+  const STATUSES = Object.values(UptakeTelemetry.STATUS);
+  for (const status of STATUSES) {
+    const expected = expectedIncrements[status] || 0;
+    const previous = snapshot1[status] || 0;
+    const current = snapshot2[status] || previous;
+    Assert.equal(expected, current - previous, `check events for ${status}`);
+  }
+}
+
+async function withFakeChannel(channel, f) {
+  const { Policy } = ChromeUtils.importESModule(
+    "resource://services-common/uptake-telemetry.sys.mjs"
+  );
+  let oldGetChannel = Policy.getChannel;
+  Policy.getChannel = () => channel;
+  try {
+    return await f();
+  } finally {
+    Policy.getChannel = oldGetChannel;
+  }
+}
+
+function arrayEqual(a, b) {
+  return JSON.stringify(a) == JSON.stringify(b);
+}
diff --git a/services/common/tests/unit/head_http.js b/services/common/tests/unit/head_http.js
new file mode 100644
index 0000000000..6c2a0a3f0f
--- /dev/null
+++ b/services/common/tests/unit/head_http.js
@@ -0,0 +1,33 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+/* import-globals-from head_global.js */
+
+var { CommonUtils } = ChromeUtils.importESModule(
+  "resource://services-common/utils.sys.mjs"
+);
+
+function basic_auth_header(user, password) {
+  return "Basic " + btoa(user + ":" + CommonUtils.encodeUTF8(password));
+}
+
+function basic_auth_matches(req, user, password) {
+  if (!req.hasHeader("Authorization")) {
+    return false;
+  }
+
+  let expected = basic_auth_header(user, CommonUtils.encodeUTF8(password));
+  return req.getHeader("Authorization") == expected;
+}
+
+function httpd_basic_auth_handler(body, metadata, response) {
+  if (basic_auth_matches(metadata, "guest", "guest")) {
+    response.setStatusLine(metadata.httpVersion, 200, "OK, authorized");
+    response.setHeader("WWW-Authenticate", 'Basic realm="secret"', false);
+  } else {
+    body = "This path exists and is protected - failed";
+    response.setStatusLine(metadata.httpVersion, 401, "Unauthorized");
+    response.setHeader("WWW-Authenticate", 'Basic realm="secret"', false);
+  }
+  response.bodyOutputStream.write(body, body.length);
+}
diff --git a/services/common/tests/unit/moz.build b/services/common/tests/unit/moz.build
new file mode 100644
index 0000000000..568f361a54
--- /dev/null
+++ b/services/common/tests/unit/moz.build
@@ -0,0 +1,5 @@
+# -*- 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/.
diff --git a/services/common/tests/unit/test_async_chain.js b/services/common/tests/unit/test_async_chain.js
new file mode 100644
index 0000000000..3277c92f81
--- /dev/null
+++ b/services/common/tests/unit/test_async_chain.js
@@ -0,0 +1,40 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { Async } = ChromeUtils.importESModule(
+  "resource://services-common/async.sys.mjs"
+);
+
+function run_test() {
+  _("Chain a few async methods, making sure the 'this' object is correct.");
+
+  let methods = {
+    save(x, callback) {
+      this.x = x;
+      callback(x);
+    },
+    addX(x, callback) {
+      callback(x + this.x);
+    },
+    double(x, callback) {
+      callback(x * 2);
+    },
+    neg(x, callback) {
+      callback(-x);
+    },
+  };
+  methods.chain = Async.chain;
+
+  // ((1 + 1 + 1) * (-1) + 1) * 2 + 1 = -3
+  methods.chain(
+    methods.save,
+    methods.addX,
+    methods.addX,
+    methods.neg,
+    methods.addX,
+    methods.double,
+    methods.addX,
+    methods.save
+  )(1);
+  Assert.equal(methods.x, -3);
+}
diff --git a/services/common/tests/unit/test_async_foreach.js b/services/common/tests/unit/test_async_foreach.js
new file mode 100644
index 0000000000..14a23e7ff7
--- /dev/null
+++ b/services/common/tests/unit/test_async_foreach.js
@@ -0,0 +1,88 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { Async } = ChromeUtils.importESModule(
+  "resource://services-common/async.sys.mjs"
+);
+const { sinon } = ChromeUtils.importESModule(
+  "resource://testing-common/Sinon.sys.mjs"
+);
+
+function makeArray(length) {
+  // Start at 1 so that we can just divide by yieldEvery to get the expected
+  // call count. (we exp)
+  return Array.from({ length }, (v, i) => i + 1);
+}
+
+// Adjust if we ever change the default.
+const DEFAULT_YIELD_EVERY = 50;
+
+add_task(async function testYields() {
+  let spy = sinon.spy(Async, "promiseYield");
+  try {
+    await Async.yieldingForEach(makeArray(DEFAULT_YIELD_EVERY * 2), element => {
+      // The yield will happen *after* this function is ran.
+      Assert.equal(
+        spy.callCount,
+        Math.floor((element - 1) / DEFAULT_YIELD_EVERY)
+      );
+    });
+  } finally {
+    spy.restore();
+  }
+});
+
+add_task(async function testExistingYieldState() {
+  const yieldState = Async.yieldState(DEFAULT_YIELD_EVERY);
+
+  for (let i = 0; i < 15; i++) {
+    Assert.equal(yieldState.shouldYield(), false);
+  }
+
+  let spy = sinon.spy(Async, "promiseYield");
+
+  try {
+    await Async.yieldingForEach(
+      makeArray(DEFAULT_YIELD_EVERY * 2),
+      element => {
+        Assert.equal(
+          spy.callCount,
+          Math.floor((element + 15 - 1) / DEFAULT_YIELD_EVERY)
+        );
+      },
+      yieldState
+    );
+  } finally {
+    spy.restore();
+  }
+});
+
+add_task(async function testEarlyReturn() {
+  let lastElement = 0;
+  await Async.yieldingForEach(makeArray(DEFAULT_YIELD_EVERY), element => {
+    lastElement = element;
+    return element === 10;
+  });
+
+  Assert.equal(lastElement, 10);
+});
+
+add_task(async function testEaryReturnAsync() {
+  let lastElement = 0;
+  await Async.yieldingForEach(makeArray(DEFAULT_YIELD_EVERY), async element => {
+    lastElement = element;
+    return element === 10;
+  });
+
+  Assert.equal(lastElement, 10);
+});
+
+add_task(async function testEarlyReturnPromise() {
+  let lastElement = 0;
+  await Async.yieldingForEach(makeArray(DEFAULT_YIELD_EVERY), element => {
+    lastElement = element;
+    return new Promise(resolve => resolve(element === 10));
+  });
+
+  Assert.equal(lastElement, 10);
+});
diff --git a/services/common/tests/unit/test_hawkclient.js b/services/common/tests/unit/test_hawkclient.js
new file mode 100644
index 0000000000..33d125f42e
--- /dev/null
+++ b/services/common/tests/unit/test_hawkclient.js
@@ -0,0 +1,515 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const { HawkClient } = ChromeUtils.importESModule(
+  "resource://services-common/hawkclient.sys.mjs"
+);
+
+const SECOND_MS = 1000;
+const MINUTE_MS = SECOND_MS * 60;
+const HOUR_MS = MINUTE_MS * 60;
+
+const TEST_CREDS = {
+  id: "eyJleHBpcmVzIjogMTM2NTAxMDg5OC4x",
+  key: "qTZf4ZFpAMpMoeSsX3zVRjiqmNs=",
+  algorithm: "sha256",
+};
+
+initTestLogging("Trace");
+
+add_task(function test_now() {
+  let client = new HawkClient("https://example.com");
+
+  Assert.ok(client.now() - Date.now() < SECOND_MS);
+});
+
+add_task(function test_updateClockOffset() {
+  let client = new HawkClient("https://example.com");
+
+  let now = new Date();
+  let serverDate = now.toUTCString();
+
+  // Client's clock is off
+  client.now = () => {
+    return now.valueOf() + HOUR_MS;
+  };
+
+  client._updateClockOffset(serverDate);
+
+  // Check that they're close; there will likely be a one-second rounding
+  // error, so checking strict equality will likely fail.
+  //
+  // localtimeOffsetMsec is how many milliseconds to add to the local clock so
+  // that it agrees with the server.  We are one hour ahead of the server, so
+  // our offset should be -1 hour.
+  Assert.ok(Math.abs(client.localtimeOffsetMsec + HOUR_MS) <= SECOND_MS);
+});
+
+add_task(async function test_authenticated_get_request() {
+  let message = '{"msg": "Great Success!"}';
+  let method = "GET";
+
+  let server = httpd_setup({
+    "/foo": (request, response) => {
+      Assert.ok(request.hasHeader("Authorization"));
+
+      response.setStatusLine(request.httpVersion, 200, "OK");
+      response.bodyOutputStream.write(message, message.length);
+    },
+  });
+
+  let client = new HawkClient(server.baseURI);
+
+  let response = await client.request("/foo", method, TEST_CREDS);
+  let result = JSON.parse(response.body);
+
+  Assert.equal("Great Success!", result.msg);
+
+  await promiseStopServer(server);
+});
+
+async function check_authenticated_request(method) {
+  let server = httpd_setup({
+    "/foo": (request, response) => {
+      Assert.ok(request.hasHeader("Authorization"));
+
+      response.setStatusLine(request.httpVersion, 200, "OK");
+      response.setHeader("Content-Type", "application/json");
+      response.bodyOutputStream.writeFrom(
+        request.bodyInputStream,
+        request.bodyInputStream.available()
+      );
+    },
+  });
+
+  let client = new HawkClient(server.baseURI);
+
+  let response = await client.request("/foo", method, TEST_CREDS, {
+    foo: "bar",
+  });
+  let result = JSON.parse(response.body);
+
+  Assert.equal("bar", result.foo);
+
+  await promiseStopServer(server);
+}
+
+add_task(async function test_authenticated_post_request() {
+  await check_authenticated_request("POST");
+});
+
+add_task(async function test_authenticated_put_request() {
+  await check_authenticated_request("PUT");
+});
+
+add_task(async function test_authenticated_patch_request() {
+  await check_authenticated_request("PATCH");
+});
+
+add_task(async function test_extra_headers() {
+  let server = httpd_setup({
+    "/foo": (request, response) => {
+      Assert.ok(request.hasHeader("Authorization"));
+      Assert.ok(request.hasHeader("myHeader"));
+      Assert.equal(request.getHeader("myHeader"), "fake");
+
+      response.setStatusLine(request.httpVersion, 200, "OK");
+      response.setHeader("Content-Type", "application/json");
+      response.bodyOutputStream.writeFrom(
+        request.bodyInputStream,
+        request.bodyInputStream.available()
+      );
+    },
+  });
+
+  let client = new HawkClient(server.baseURI);
+
+  let response = await client.request(
+    "/foo",
+    "POST",
+    TEST_CREDS,
+    { foo: "bar" },
+    { myHeader: "fake" }
+  );
+  let result = JSON.parse(response.body);
+
+  Assert.equal("bar", result.foo);
+
+  await promiseStopServer(server);
+});
+
+add_task(async function test_credentials_optional() {
+  let method = "GET";
+  let server = httpd_setup({
+    "/foo": (request, response) => {
+      Assert.ok(!request.hasHeader("Authorization"));
+
+      let message = JSON.stringify({ msg: "you're in the friend zone" });
+      response.setStatusLine(request.httpVersion, 200, "OK");
+      response.setHeader("Content-Type", "application/json");
+      response.bodyOutputStream.write(message, message.length);
+    },
+  });
+
+  let client = new HawkClient(server.baseURI);
+  let result = await client.request("/foo", method); // credentials undefined
+  Assert.equal(JSON.parse(result.body).msg, "you're in the friend zone");
+
+  await promiseStopServer(server);
+});
+
+add_task(async function test_server_error() {
+  let message = "Ohai!";
+  let method = "GET";
+
+  let server = httpd_setup({
+    "/foo": (request, response) => {
+      response.setStatusLine(request.httpVersion, 418, "I am a Teapot");
+      response.bodyOutputStream.write(message, message.length);
+    },
+  });
+
+  let client = new HawkClient(server.baseURI);
+
+  try {
+    await client.request("/foo", method, TEST_CREDS);
+    do_throw("Expected an error");
+  } catch (err) {
+    Assert.equal(418, err.code);
+    Assert.equal("I am a Teapot", err.message);
+  }
+
+  await promiseStopServer(server);
+});
+
+add_task(async function test_server_error_json() {
+  let message = JSON.stringify({ error: "Cannot get ye flask." });
+  let method = "GET";
+
+  let server = httpd_setup({
+    "/foo": (request, response) => {
+      response.setStatusLine(
+        request.httpVersion,
+        400,
+        "What wouldst thou deau?"
+      );
+      response.bodyOutputStream.write(message, message.length);
+    },
+  });
+
+  let client = new HawkClient(server.baseURI);
+
+  try {
+    await client.request("/foo", method, TEST_CREDS);
+    do_throw("Expected an error");
+  } catch (err) {
+    Assert.equal("Cannot get ye flask.", err.error);
+  }
+
+  await promiseStopServer(server);
+});
+
+add_task(async function test_offset_after_request() {
+  let message = "Ohai!";
+  let method = "GET";
+
+  let server = httpd_setup({
+    "/foo": (request, response) => {
+      response.setStatusLine(request.httpVersion, 200, "OK");
+      response.bodyOutputStream.write(message, message.length);
+    },
+  });
+
+  let client = new HawkClient(server.baseURI);
+  let now = Date.now();
+  client.now = () => {
+    return now + HOUR_MS;
+  };
+
+  Assert.equal(client.localtimeOffsetMsec, 0);
+
+  await client.request("/foo", method, TEST_CREDS);
+  // Should be about an hour off
+  Assert.ok(Math.abs(client.localtimeOffsetMsec + HOUR_MS) < SECOND_MS);
+
+  await promiseStopServer(server);
+});
+
+add_task(async function test_offset_in_hawk_header() {
+  let message = "Ohai!";
+  let method = "GET";
+
+  let server = httpd_setup({
+    "/first": function (request, response) {
+      response.setStatusLine(request.httpVersion, 200, "OK");
+      response.bodyOutputStream.write(message, message.length);
+    },
+
+    "/second": function (request, response) {
+      // We see a better date now in the ts component of the header
+      let delta = getTimestampDelta(request.getHeader("Authorization"));
+
+      // We're now within HAWK's one-minute window.
+      // I hope this isn't a recipe for intermittent oranges ...
+      if (delta < MINUTE_MS) {
+        response.setStatusLine(request.httpVersion, 200, "OK");
+      } else {
+        response.setStatusLine(request.httpVersion, 400, "Delta: " + delta);
+      }
+      response.bodyOutputStream.write(message, message.length);
+    },
+  });
+
+  let client = new HawkClient(server.baseURI);
+
+  client.now = () => {
+    return Date.now() + 12 * HOUR_MS;
+  };
+
+  // We begin with no offset
+  Assert.equal(client.localtimeOffsetMsec, 0);
+  await client.request("/first", method, TEST_CREDS);
+
+  // After the first server response, our offset is updated to -12 hours.
+  // We should be safely in the window, now.
+  Assert.ok(Math.abs(client.localtimeOffsetMsec + 12 * HOUR_MS) < MINUTE_MS);
+  await client.request("/second", method, TEST_CREDS);
+
+  await promiseStopServer(server);
+});
+
+add_task(async function test_2xx_success() {
+  // Just to ensure that we're not biased toward 200 OK for success
+  let credentials = {
+    id: "eyJleHBpcmVzIjogMTM2NTAxMDg5OC4x",
+    key: "qTZf4ZFpAMpMoeSsX3zVRjiqmNs=",
+    algorithm: "sha256",
+  };
+  let method = "GET";
+
+  let server = httpd_setup({
+    "/foo": (request, response) => {
+      response.setStatusLine(request.httpVersion, 202, "Accepted");
+    },
+  });
+
+  let client = new HawkClient(server.baseURI);
+
+  let response = await client.request("/foo", method, credentials);
+
+  // Shouldn't be any content in a 202
+  Assert.equal(response.body, "");
+
+  await promiseStopServer(server);
+});
+
+add_task(async function test_retry_request_on_fail() {
+  let attempts = 0;
+  let credentials = {
+    id: "eyJleHBpcmVzIjogMTM2NTAxMDg5OC4x",
+    key: "qTZf4ZFpAMpMoeSsX3zVRjiqmNs=",
+    algorithm: "sha256",
+  };
+  let method = "GET";
+
+  let server = httpd_setup({
+    "/maybe": function (request, response) {
+      // This path should be hit exactly twice; once with a bad timestamp, and
+      // again when the client retries the request with a corrected timestamp.
+      attempts += 1;
+      Assert.ok(attempts <= 2);
+
+      let delta = getTimestampDelta(request.getHeader("Authorization"));
+
+      // First time through, we should have a bad timestamp
+      if (attempts === 1) {
+        Assert.ok(delta > MINUTE_MS);
+        let message = "never!!!";
+        response.setStatusLine(request.httpVersion, 401, "Unauthorized");
+        response.bodyOutputStream.write(message, message.length);
+        return;
+      }
+
+      // Second time through, timestamp should be corrected by client
+      Assert.ok(delta < MINUTE_MS);
+      let message = "i love you!!!";
+      response.setStatusLine(request.httpVersion, 200, "OK");
+      response.bodyOutputStream.write(message, message.length);
+    },
+  });
+
+  let client = new HawkClient(server.baseURI);
+
+  client.now = () => {
+    return Date.now() + 12 * HOUR_MS;
+  };
+
+  // We begin with no offset
+  Assert.equal(client.localtimeOffsetMsec, 0);
+
+  // Request will have bad timestamp; client will retry once
+  let response = await client.request("/maybe", method, credentials);
+  Assert.equal(response.body, "i love you!!!");
+
+  await promiseStopServer(server);
+});
+
+add_task(async function test_multiple_401_retry_once() {
+  // Like test_retry_request_on_fail, but always return a 401
+  // and ensure that the client only retries once.
+  let attempts = 0;
+  let credentials = {
+    id: "eyJleHBpcmVzIjogMTM2NTAxMDg5OC4x",
+    key: "qTZf4ZFpAMpMoeSsX3zVRjiqmNs=",
+    algorithm: "sha256",
+  };
+  let method = "GET";
+
+  let server = httpd_setup({
+    "/maybe": function (request, response) {
+      // This path should be hit exactly twice; once with a bad timestamp, and
+      // again when the client retries the request with a corrected timestamp.
+      attempts += 1;
+
+      Assert.ok(attempts <= 2);
+
+      let message = "never!!!";
+      response.setStatusLine(request.httpVersion, 401, "Unauthorized");
+      response.bodyOutputStream.write(message, message.length);
+    },
+  });
+
+  let client = new HawkClient(server.baseURI);
+
+  client.now = () => {
+    return Date.now() - 12 * HOUR_MS;
+  };
+
+  // We begin with no offset
+  Assert.equal(client.localtimeOffsetMsec, 0);
+
+  // Request will have bad timestamp; client will retry once
+  try {
+    await client.request("/maybe", method, credentials);
+    do_throw("Expected an error");
+  } catch (err) {
+    Assert.equal(err.code, 401);
+  }
+  Assert.equal(attempts, 2);
+
+  await promiseStopServer(server);
+});
+
+add_task(async function test_500_no_retry() {
+  // If we get a 500 error, the client should not retry (as it would with a
+  // 401)
+  let credentials = {
+    id: "eyJleHBpcmVzIjogMTM2NTAxMDg5OC4x",
+    key: "qTZf4ZFpAMpMoeSsX3zVRjiqmNs=",
+    algorithm: "sha256",
+  };
+  let method = "GET";
+
+  let server = httpd_setup({
+    "/no-shutup": function (request, response) {
+      let message = "Cannot get ye flask.";
+      response.setStatusLine(request.httpVersion, 500, "Internal server error");
+      response.bodyOutputStream.write(message, message.length);
+    },
+  });
+
+  let client = new HawkClient(server.baseURI);
+
+  // Throw off the clock so the HawkClient would want to retry the request if
+  // it could
+  client.now = () => {
+    return Date.now() - 12 * HOUR_MS;
+  };
+
+  // Request will 500; no retries
+  try {
+    await client.request("/no-shutup", method, credentials);
+    do_throw("Expected an error");
+  } catch (err) {
+    Assert.equal(err.code, 500);
+  }
+
+  await promiseStopServer(server);
+});
+
+add_task(async function test_401_then_500() {
+  // Like test_multiple_401_retry_once, but return a 500 to the
+  // second request, ensuring that the promise is properly rejected
+  // in client.request.
+  let attempts = 0;
+  let credentials = {
+    id: "eyJleHBpcmVzIjogMTM2NTAxMDg5OC4x",
+    key: "qTZf4ZFpAMpMoeSsX3zVRjiqmNs=",
+    algorithm: "sha256",
+  };
+  let method = "GET";
+
+  let server = httpd_setup({
+    "/maybe": function (request, response) {
+      // This path should be hit exactly twice; once with a bad timestamp, and
+      // again when the client retries the request with a corrected timestamp.
+      attempts += 1;
+      Assert.ok(attempts <= 2);
+
+      let delta = getTimestampDelta(request.getHeader("Authorization"));
+
+      // First time through, we should have a bad timestamp
+      // Client will retry
+      if (attempts === 1) {
+        Assert.ok(delta > MINUTE_MS);
+        let message = "never!!!";
+        response.setStatusLine(request.httpVersion, 401, "Unauthorized");
+        response.bodyOutputStream.write(message, message.length);
+        return;
+      }
+
+      // Second time through, timestamp should be corrected by client
+      // And fail on the client
+      Assert.ok(delta < MINUTE_MS);
+      let message = "Cannot get ye flask.";
+      response.setStatusLine(request.httpVersion, 500, "Internal server error");
+      response.bodyOutputStream.write(message, message.length);
+    },
+  });
+
+  let client = new HawkClient(server.baseURI);
+
+  client.now = () => {
+    return Date.now() - 12 * HOUR_MS;
+  };
+
+  // We begin with no offset
+  Assert.equal(client.localtimeOffsetMsec, 0);
+
+  // Request will have bad timestamp; client will retry once
+  try {
+    await client.request("/maybe", method, credentials);
+  } catch (err) {
+    Assert.equal(err.code, 500);
+  }
+  Assert.equal(attempts, 2);
+
+  await promiseStopServer(server);
+});
+
+// End of tests.
+// Utility functions follow
+
+function getTimestampDelta(authHeader, now = Date.now()) {
+  let tsMS = new Date(
+    parseInt(/ts="(\d+)"/.exec(authHeader)[1], 10) * SECOND_MS
+  );
+  return Math.abs(tsMS - now);
+}
+
+function run_test() {
+  initTestLogging("Trace");
+  run_next_test();
+}
diff --git a/services/common/tests/unit/test_hawkrequest.js b/services/common/tests/unit/test_hawkrequest.js
new file mode 100644
index 0000000000..13ab6737de
--- /dev/null
+++ b/services/common/tests/unit/test_hawkrequest.js
@@ -0,0 +1,231 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const { HAWKAuthenticatedRESTRequest, deriveHawkCredentials } =
+  ChromeUtils.importESModule("resource://services-common/hawkrequest.sys.mjs");
+const { Async } = ChromeUtils.importESModule(
+  "resource://services-common/async.sys.mjs"
+);
+
+// https://github.com/mozilla/fxa-auth-server/wiki/onepw-protocol#wiki-use-session-certificatesign-etc
+var SESSION_KEYS = {
+  sessionToken: h(
+    // eslint-disable-next-line no-useless-concat
+    "a0a1a2a3a4a5a6a7 a8a9aaabacadaeaf" + "b0b1b2b3b4b5b6b7 b8b9babbbcbdbebf"
+  ),
+
+  tokenID: h(
+    // eslint-disable-next-line no-useless-concat
+    "c0a29dcf46174973 da1378696e4c82ae" + "10f723cf4f4d9f75 e39f4ae3851595ab"
+  ),
+
+  reqHMACkey: h(
+    // eslint-disable-next-line no-useless-concat
+    "9d8f22998ee7f579 8b887042466b72d5" + "3e56ab0c094388bf 65831f702d2febc0"
+  ),
+};
+
+function do_register_cleanup() {
+  Services.prefs.clearUserPref("intl.accept_languages");
+  Services.prefs.clearUserPref("services.common.log.logger.rest.request");
+
+  // remove the pref change listener
+  let hawk = new HAWKAuthenticatedRESTRequest("https://example.com");
+  hawk._intl.uninit();
+}
+
+function run_test() {
+  registerCleanupFunction(do_register_cleanup);
+
+  Services.prefs.setStringPref(
+    "services.common.log.logger.rest.request",
+    "Trace"
+  );
+  initTestLogging("Trace");
+
+  run_next_test();
+}
+
+add_test(function test_intl_accept_language() {
+  let testCount = 0;
+  let languages = [
+    "zu-NP;vo", // Nepalese dialect of Zulu, defaulting to Volapük
+    "fa-CG;ik", // Congolese dialect of Farsei, defaulting to Inupiaq
+  ];
+
+  function setLanguagePref(lang) {
+    Services.prefs.setStringPref("intl.accept_languages", lang);
+  }
+
+  let hawk = new HAWKAuthenticatedRESTRequest("https://example.com");
+
+  Services.prefs.addObserver("intl.accept_languages", checkLanguagePref);
+  setLanguagePref(languages[testCount]);
+
+  function checkLanguagePref() {
+    CommonUtils.nextTick(function () {
+      // Ensure we're only called for the number of entries in languages[].
+      Assert.ok(testCount < languages.length);
+
+      Assert.equal(hawk._intl.accept_languages, languages[testCount]);
+
+      testCount++;
+      if (testCount < languages.length) {
+        // Set next language in prefs; Pref service will call checkNextLanguage.
+        setLanguagePref(languages[testCount]);
+        return;
+      }
+
+      // We've checked all the entries in languages[]. Cleanup and move on.
+      info(
+        "Checked " +
+          testCount +
+          " languages. Removing checkLanguagePref as pref observer."
+      );
+      Services.prefs.removeObserver("intl.accept_languages", checkLanguagePref);
+      run_next_test();
+    });
+  }
+});
+
+add_task(async function test_hawk_authenticated_request() {
+  let postData = { your: "data" };
+
+  // An arbitrary date - Feb 2, 1971.  It ends in a bunch of zeroes to make our
+  // computation with the hawk timestamp easier, since hawk throws away the
+  // millisecond values.
+  let then = 34329600000;
+
+  let clockSkew = 120000;
+  let timeOffset = -1 * clockSkew;
+  let localTime = then + clockSkew;
+
+  // Set the accept-languages pref to the Nepalese dialect of Zulu.
+  let acceptLanguage = "zu-NP"; // omit trailing ';', which our HTTP libs snip
+  Services.prefs.setStringPref("intl.accept_languages", acceptLanguage);
+
+  let credentials = {
+    id: "eyJleHBpcmVzIjogMTM2NTAxMDg5OC4x",
+    key: "qTZf4ZFpAMpMoeSsX3zVRjiqmNs=",
+    algorithm: "sha256",
+  };
+
+  let server = httpd_setup({
+    "/elysium": function (request, response) {
+      Assert.ok(request.hasHeader("Authorization"));
+
+      // check that the header timestamp is our arbitrary system date, not
+      // today's date.  Note that hawk header timestamps are in seconds, not
+      // milliseconds.
+      let authorization = request.getHeader("Authorization");
+      let tsMS = parseInt(/ts="(\d+)"/.exec(authorization)[1], 10) * 1000;
+      Assert.equal(tsMS, then);
+
+      // This testing can be a little wonky. In an environment where
+      //   pref("intl.accept_languages") === 'en-US, en'
+      // the header is sent as:
+      //   'en-US,en;q=0.5'
+      // hence our fake value for acceptLanguage.
+      let lang = request.getHeader("Accept-Language");
+      Assert.equal(lang, acceptLanguage);
+
+      let message = "yay";
+      response.setStatusLine(request.httpVersion, 200, "OK");
+      response.bodyOutputStream.write(message, message.length);
+    },
+  });
+
+  let url = server.baseURI + "/elysium";
+  let extra = {
+    now: localTime,
+    localtimeOffsetMsec: timeOffset,
+  };
+
+  let request = new HAWKAuthenticatedRESTRequest(url, credentials, extra);
+
+  // Allow hawk._intl to respond to the language pref change
+  await Async.promiseYield();
+
+  await request.post(postData);
+  Assert.equal(200, request.response.status);
+  Assert.equal(request.response.body, "yay");
+
+  Services.prefs.clearUserPref("intl.accept_languages");
+  let pref = Services.prefs.getComplexValue(
+    "intl.accept_languages",
+    Ci.nsIPrefLocalizedString
+  );
+  Assert.notEqual(acceptLanguage, pref.data);
+
+  await promiseStopServer(server);
+});
+
+add_task(async function test_hawk_language_pref_changed() {
+  let languages = [
+    "zu-NP", // Nepalese dialect of Zulu
+    "fa-CG", // Congolese dialect of Farsi
+  ];
+
+  let credentials = {
+    id: "eyJleHBpcmVzIjogMTM2NTAxMDg5OC4x",
+    key: "qTZf4ZFpAMpMoeSsX3zVRjiqmNs=",
+    algorithm: "sha256",
+  };
+
+  function setLanguage(lang) {
+    Services.prefs.setStringPref("intl.accept_languages", lang);
+  }
+
+  let server = httpd_setup({
+    "/foo": function (request, response) {
+      Assert.equal(languages[1], request.getHeader("Accept-Language"));
+
+      response.setStatusLine(request.httpVersion, 200, "OK");
+    },
+  });
+
+  let url = server.baseURI + "/foo";
+  let request;
+
+  setLanguage(languages[0]);
+
+  // A new request should create the stateful object for tracking the current
+  // language.
+  request = new HAWKAuthenticatedRESTRequest(url, credentials);
+
+  // Wait for change to propagate
+  await Async.promiseYield();
+  Assert.equal(languages[0], request._intl.accept_languages);
+
+  // Change the language pref ...
+  setLanguage(languages[1]);
+
+  await Async.promiseYield();
+
+  request = new HAWKAuthenticatedRESTRequest(url, credentials);
+  let response = await request.post({});
+
+  Assert.equal(200, response.status);
+  Services.prefs.clearUserPref("intl.accept_languages");
+
+  await promiseStopServer(server);
+});
+
+add_task(async function test_deriveHawkCredentials() {
+  let credentials = await deriveHawkCredentials(
+    SESSION_KEYS.sessionToken,
+    "sessionToken"
+  );
+  Assert.equal(credentials.id, SESSION_KEYS.tokenID);
+  Assert.equal(
+    CommonUtils.bytesAsHex(credentials.key),
+    SESSION_KEYS.reqHMACkey
+  );
+});
+
+// turn formatted test vectors into normal hex strings
+function h(hexStr) {
+  return hexStr.replace(/\s+/g, "");
+}
diff --git a/services/common/tests/unit/test_kinto.js b/services/common/tests/unit/test_kinto.js
new file mode 100644
index 0000000000..4b5e8471b1
--- /dev/null
+++ b/services/common/tests/unit/test_kinto.js
@@ -0,0 +1,512 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { Kinto } = ChromeUtils.import(
+  "resource://services-common/kinto-offline-client.js"
+);
+const { FirefoxAdapter } = ChromeUtils.importESModule(
+  "resource://services-common/kinto-storage-adapter.sys.mjs"
+);
+
+var server;
+
+// set up what we need to make storage adapters
+const kintoFilename = "kinto.sqlite";
+
+function do_get_kinto_sqliteHandle() {
+  return FirefoxAdapter.openConnection({ path: kintoFilename });
+}
+
+function do_get_kinto_collection(sqliteHandle, collection = "test_collection") {
+  let config = {
+    remote: `http://localhost:${server.identity.primaryPort}/v1/`,
+    headers: { Authorization: "Basic " + btoa("user:pass") },
+    adapter: FirefoxAdapter,
+    adapterOptions: { sqliteHandle },
+  };
+  return new Kinto(config).collection(collection);
+}
+
+async function clear_collection() {
+  let sqliteHandle;
+  try {
+    sqliteHandle = await do_get_kinto_sqliteHandle();
+    const collection = do_get_kinto_collection(sqliteHandle);
+    await collection.clear();
+  } finally {
+    await sqliteHandle.close();
+  }
+}
+
+// test some operations on a local collection
+add_task(async function test_kinto_add_get() {
+  let sqliteHandle;
+  try {
+    sqliteHandle = await do_get_kinto_sqliteHandle();
+    const collection = do_get_kinto_collection(sqliteHandle);
+
+    let newRecord = { foo: "bar" };
+    // check a record is created
+    let createResult = await collection.create(newRecord);
+    Assert.equal(createResult.data.foo, newRecord.foo);
+    // check getting the record gets the same info
+    let getResult = await collection.get(createResult.data.id);
+    deepEqual(createResult.data, getResult.data);
+    // check what happens if we create the same item again (it should throw
+    // since you can't create with id)
+    try {
+      await collection.create(createResult.data);
+      do_throw("Creation of a record with an id should fail");
+    } catch (err) {}
+    // try a few creates without waiting for the first few to resolve
+    let promises = [];
+    promises.push(collection.create(newRecord));
+    promises.push(collection.create(newRecord));
+    promises.push(collection.create(newRecord));
+    await collection.create(newRecord);
+    await Promise.all(promises);
+  } finally {
+    await sqliteHandle.close();
+  }
+});
+
+add_task(clear_collection);
+
+// test some operations on multiple connections
+add_task(async function test_kinto_add_get() {
+  let sqliteHandle;
+  try {
+    sqliteHandle = await do_get_kinto_sqliteHandle();
+    const collection1 = do_get_kinto_collection(sqliteHandle);
+    const collection2 = do_get_kinto_collection(
+      sqliteHandle,
+      "test_collection_2"
+    );
+
+    let newRecord = { foo: "bar" };
+
+    // perform several write operations alternately without waiting for promises
+    // to resolve
+    let promises = [];
+    for (let i = 0; i < 10; i++) {
+      promises.push(collection1.create(newRecord));
+      promises.push(collection2.create(newRecord));
+    }
+
+    // ensure subsequent operations still work
+    await Promise.all([
+      collection1.create(newRecord),
+      collection2.create(newRecord),
+    ]);
+    await Promise.all(promises);
+  } finally {
+    await sqliteHandle.close();
+  }
+});
+
+add_task(clear_collection);
+
+add_task(async function test_kinto_update() {
+  let sqliteHandle;
+  try {
+    sqliteHandle = await do_get_kinto_sqliteHandle();
+    const collection = do_get_kinto_collection(sqliteHandle);
+    const newRecord = { foo: "bar" };
+    // check a record is created
+    let createResult = await collection.create(newRecord);
+    Assert.equal(createResult.data.foo, newRecord.foo);
+    Assert.equal(createResult.data._status, "created");
+    // check we can update this OK
+    let copiedRecord = Object.assign(createResult.data, {});
+    deepEqual(createResult.data, copiedRecord);
+    copiedRecord.foo = "wibble";
+    let updateResult = await collection.update(copiedRecord);
+    // check the field was updated
+    Assert.equal(updateResult.data.foo, copiedRecord.foo);
+    // check the status is still "created", since we haven't synced
+    // the record
+    Assert.equal(updateResult.data._status, "created");
+  } finally {
+    await sqliteHandle.close();
+  }
+});
+
+add_task(clear_collection);
+
+add_task(async function test_kinto_clear() {
+  let sqliteHandle;
+  try {
+    sqliteHandle = await do_get_kinto_sqliteHandle();
+    const collection = do_get_kinto_collection(sqliteHandle);
+
+    // create an expected number of records
+    const expected = 10;
+    const newRecord = { foo: "bar" };
+    for (let i = 0; i < expected; i++) {
+      await collection.create(newRecord);
+    }
+    // check the collection contains the correct number
+    let list = await collection.list();
+    Assert.equal(list.data.length, expected);
+    // clear the collection and check again - should be 0
+    await collection.clear();
+    list = await collection.list();
+    Assert.equal(list.data.length, 0);
+  } finally {
+    await sqliteHandle.close();
+  }
+});
+
+add_task(clear_collection);
+
+add_task(async function test_kinto_delete() {
+  let sqliteHandle;
+  try {
+    sqliteHandle = await do_get_kinto_sqliteHandle();
+    const collection = do_get_kinto_collection(sqliteHandle);
+    const newRecord = { foo: "bar" };
+    // check a record is created
+    let createResult = await collection.create(newRecord);
+    Assert.equal(createResult.data.foo, newRecord.foo);
+    // check getting the record gets the same info
+    let getResult = await collection.get(createResult.data.id);
+    deepEqual(createResult.data, getResult.data);
+    // delete that record
+    let deleteResult = await collection.delete(createResult.data.id);
+    // check the ID is set on the result
+    Assert.equal(getResult.data.id, deleteResult.data.id);
+    // and check that get no longer returns the record
+    try {
+      getResult = await collection.get(createResult.data.id);
+      do_throw("there should not be a result");
+    } catch (e) {}
+  } finally {
+    await sqliteHandle.close();
+  }
+});
+
+add_task(async function test_kinto_list() {
+  let sqliteHandle;
+  try {
+    sqliteHandle = await do_get_kinto_sqliteHandle();
+    const collection = do_get_kinto_collection(sqliteHandle);
+    const expected = 10;
+    const created = [];
+    for (let i = 0; i < expected; i++) {
+      let newRecord = { foo: "test " + i };
+      let createResult = await collection.create(newRecord);
+      created.push(createResult.data);
+    }
+    // check the collection contains the correct number
+    let list = await collection.list();
+    Assert.equal(list.data.length, expected);
+
+    // check that all created records exist in the retrieved list
+    for (let createdRecord of created) {
+      let found = false;
+      for (let retrievedRecord of list.data) {
+        if (createdRecord.id == retrievedRecord.id) {
+          deepEqual(createdRecord, retrievedRecord);
+          found = true;
+        }
+      }
+      Assert.ok(found);
+    }
+  } finally {
+    await sqliteHandle.close();
+  }
+});
+
+add_task(clear_collection);
+
+add_task(async function test_importBulk_ignores_already_imported_records() {
+  let sqliteHandle;
+  try {
+    sqliteHandle = await do_get_kinto_sqliteHandle();
+    const collection = do_get_kinto_collection(sqliteHandle);
+    const record = {
+      id: "41b71c13-17e9-4ee3-9268-6a41abf9730f",
+      title: "foo",
+      last_modified: 1457896541,
+    };
+    await collection.importBulk([record]);
+    let impactedRecords = await collection.importBulk([record]);
+    Assert.equal(impactedRecords.length, 0);
+  } finally {
+    await sqliteHandle.close();
+  }
+});
+
+add_task(clear_collection);
+
+add_task(async function test_loadDump_should_overwrite_old_records() {
+  let sqliteHandle;
+  try {
+    sqliteHandle = await do_get_kinto_sqliteHandle();
+    const collection = do_get_kinto_collection(sqliteHandle);
+    const record = {
+      id: "41b71c13-17e9-4ee3-9268-6a41abf9730f",
+      title: "foo",
+      last_modified: 1457896541,
+    };
+    await collection.loadDump([record]);
+    const updated = Object.assign({}, record, { last_modified: 1457896543 });
+    let impactedRecords = await collection.loadDump([updated]);
+    Assert.equal(impactedRecords.length, 1);
+  } finally {
+    await sqliteHandle.close();
+  }
+});
+
+add_task(clear_collection);
+
+add_task(async function test_loadDump_should_not_overwrite_unsynced_records() {
+  let sqliteHandle;
+  try {
+    sqliteHandle = await do_get_kinto_sqliteHandle();
+    const collection = do_get_kinto_collection(sqliteHandle);
+    const recordId = "41b71c13-17e9-4ee3-9268-6a41abf9730f";
+    await collection.create(
+      { id: recordId, title: "foo" },
+      { useRecordId: true }
+    );
+    const record = { id: recordId, title: "bar", last_modified: 1457896541 };
+    let impactedRecords = await collection.loadDump([record]);
+    Assert.equal(impactedRecords.length, 0);
+  } finally {
+    await sqliteHandle.close();
+  }
+});
+
+add_task(clear_collection);
+
+add_task(
+  async function test_loadDump_should_not_overwrite_records_without_last_modified() {
+    let sqliteHandle;
+    try {
+      sqliteHandle = await do_get_kinto_sqliteHandle();
+      const collection = do_get_kinto_collection(sqliteHandle);
+      const recordId = "41b71c13-17e9-4ee3-9268-6a41abf9730f";
+      await collection.create({ id: recordId, title: "foo" }, { synced: true });
+      const record = { id: recordId, title: "bar", last_modified: 1457896541 };
+      let impactedRecords = await collection.loadDump([record]);
+      Assert.equal(impactedRecords.length, 0);
+    } finally {
+      await sqliteHandle.close();
+    }
+  }
+);
+
+add_task(clear_collection);
+
+// Now do some sanity checks against a server - we're not looking to test
+// core kinto.js functionality here (there is excellent test coverage in
+// kinto.js), more making sure things are basically working as expected.
+add_task(async function test_kinto_sync() {
+  const configPath = "/v1/";
+  const metadataPath = "/v1/buckets/default/collections/test_collection";
+  const recordsPath = "/v1/buckets/default/collections/test_collection/records";
+  // register a handler
+  function handleResponse(request, response) {
+    try {
+      const sampled = getSampleResponse(request, server.identity.primaryPort);
+      if (!sampled) {
+        do_throw(
+          `unexpected ${request.method} request for ${request.path}?${request.queryString}`
+        );
+      }
+
+      response.setStatusLine(
+        null,
+        sampled.status.status,
+        sampled.status.statusText
+      );
+      // send the headers
+      for (let headerLine of sampled.sampleHeaders) {
+        let headerElements = headerLine.split(":");
+        response.setHeader(headerElements[0], headerElements[1].trimLeft());
+      }
+      response.setHeader("Date", new Date().toUTCString());
+
+      response.write(sampled.responseBody);
+    } catch (e) {
+      dump(`${e}\n`);
+    }
+  }
+  server.registerPathHandler(configPath, handleResponse);
+  server.registerPathHandler(metadataPath, handleResponse);
+  server.registerPathHandler(recordsPath, handleResponse);
+
+  // create an empty collection, sync to populate
+  let sqliteHandle;
+  try {
+    let result;
+    sqliteHandle = await do_get_kinto_sqliteHandle();
+    const collection = do_get_kinto_collection(sqliteHandle);
+
+    result = await collection.sync();
+    Assert.ok(result.ok);
+
+    // our test data has a single record; it should be in the local collection
+    let list = await collection.list();
+    Assert.equal(list.data.length, 1);
+
+    // now sync again; we should now have 2 records
+    result = await collection.sync();
+    Assert.ok(result.ok);
+    list = await collection.list();
+    Assert.equal(list.data.length, 2);
+
+    // sync again; the second records should have been modified
+    const before = list.data[0].title;
+    result = await collection.sync();
+    Assert.ok(result.ok);
+    list = await collection.list();
+    const after = list.data[1].title;
+    Assert.notEqual(before, after);
+
+    const manualID = list.data[0].id;
+    Assert.equal(list.data.length, 3);
+    Assert.equal(manualID, "some-manually-chosen-id");
+  } finally {
+    await sqliteHandle.close();
+  }
+});
+
+function run_test() {
+  // Set up an HTTP Server
+  server = new HttpServer();
+  server.start(-1);
+
+  run_next_test();
+
+  registerCleanupFunction(function () {
+    server.stop(function () {});
+  });
+}
+
+// get a response for a given request from sample data
+function getSampleResponse(req, port) {
+  const responses = {
+    OPTIONS: {
+      sampleHeaders: [
+        "Access-Control-Allow-Headers: Content-Length,Expires,Backoff,Retry-After,Last-Modified,Total-Records,ETag,Pragma,Cache-Control,authorization,content-type,if-none-match,Alert,Next-Page",
+        "Access-Control-Allow-Methods: GET,HEAD,OPTIONS,POST,DELETE,OPTIONS",
+        "Access-Control-Allow-Origin: *",
+        "Content-Type: application/json; charset=UTF-8",
+        "Server: waitress",
+      ],
+      status: { status: 200, statusText: "OK" },
+      responseBody: "null",
+    },
+    "GET:/v1/?": {
+      sampleHeaders: [
+        "Access-Control-Allow-Origin: *",
+        "Access-Control-Expose-Headers: Retry-After, Content-Length, Alert, Backoff",
+        "Content-Type: application/json; charset=UTF-8",
+        "Server: waitress",
+      ],
+      status: { status: 200, statusText: "OK" },
+      responseBody: JSON.stringify({
+        settings: {
+          batch_max_requests: 25,
+        },
+        url: `http://localhost:${port}/v1/`,
+        documentation: "https://kinto.readthedocs.org/",
+        version: "1.5.1",
+        commit: "cbc6f58",
+        hello: "kinto",
+      }),
+    },
+    "GET:/v1/buckets/default/collections/test_collection": {
+      sampleHeaders: [
+        "Access-Control-Allow-Origin: *",
+        "Access-Control-Expose-Headers: Retry-After, Content-Length, Alert, Backoff",
+        "Content-Type: application/json; charset=UTF-8",
+        "Server: waitress",
+        'Etag: "1234"',
+      ],
+      status: { status: 200, statusText: "OK" },
+      responseBody: JSON.stringify({
+        data: {
+          id: "test_collection",
+          last_modified: 1234,
+        },
+      }),
+    },
+    "GET:/v1/buckets/default/collections/test_collection/records?_sort=-last_modified":
+      {
+        sampleHeaders: [
+          "Access-Control-Allow-Origin: *",
+          "Access-Control-Expose-Headers: Retry-After, Content-Length, Alert, Backoff",
+          "Content-Type: application/json; charset=UTF-8",
+          "Server: waitress",
+          'Etag: "1445606341071"',
+        ],
+        status: { status: 200, statusText: "OK" },
+        responseBody: JSON.stringify({
+          data: [
+            {
+              last_modified: 1445606341071,
+              done: false,
+              id: "68db8313-686e-4fff-835e-07d78ad6f2af",
+              title: "New test",
+            },
+          ],
+        }),
+      },
+    "GET:/v1/buckets/default/collections/test_collection/records?_sort=-last_modified&_since=1445606341071":
+      {
+        sampleHeaders: [
+          "Access-Control-Allow-Origin: *",
+          "Access-Control-Expose-Headers: Retry-After, Content-Length, Alert, Backoff",
+          "Content-Type: application/json; charset=UTF-8",
+          "Server: waitress",
+          'Etag: "1445607941223"',
+        ],
+        status: { status: 200, statusText: "OK" },
+        responseBody: JSON.stringify({
+          data: [
+            {
+              last_modified: 1445607941223,
+              done: false,
+              id: "901967b0-f729-4b30-8d8d-499cba7f4b1d",
+              title: "Another new test",
+            },
+          ],
+        }),
+      },
+    "GET:/v1/buckets/default/collections/test_collection/records?_sort=-last_modified&_since=1445607941223":
+      {
+        sampleHeaders: [
+          "Access-Control-Allow-Origin: *",
+          "Access-Control-Expose-Headers: Retry-After, Content-Length, Alert, Backoff",
+          "Content-Type: application/json; charset=UTF-8",
+          "Server: waitress",
+          'Etag: "1445607541267"',
+        ],
+        status: { status: 200, statusText: "OK" },
+        responseBody: JSON.stringify({
+          data: [
+            {
+              last_modified: 1445607541265,
+              done: false,
+              id: "901967b0-f729-4b30-8d8d-499cba7f4b1d",
+              title: "Modified title",
+            },
+            {
+              last_modified: 1445607541267,
+              done: true,
+              id: "some-manually-chosen-id",
+              title: "New record with custom ID",
+            },
+          ],
+        }),
+      },
+  };
+  return (
+    responses[`${req.method}:${req.path}?${req.queryString}`] ||
+    responses[`${req.method}:${req.path}`] ||
+    responses[req.method]
+  );
+}
diff --git a/services/common/tests/unit/test_load_modules.js b/services/common/tests/unit/test_load_modules.js
new file mode 100644
index 0000000000..0c80899e1c
--- /dev/null
+++ b/services/common/tests/unit/test_load_modules.js
@@ -0,0 +1,55 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { AppConstants } = ChromeUtils.importESModule(
+  "resource://gre/modules/AppConstants.sys.mjs"
+);
+
+const MODULE_BASE = "resource://services-common/";
+const shared_modules = ["async.js", "logmanager.js", "rest.js", "utils.js"];
+
+const non_android_modules = ["tokenserverclient.js"];
+
+const TEST_BASE = "resource://testing-common/services/common/";
+const shared_test_modules = ["logging.js"];
+
+function expectImportsToSucceed(mm, base = MODULE_BASE) {
+  for (let m of mm) {
+    let resource = base + m;
+    let succeeded = false;
+    try {
+      ChromeUtils.import(resource);
+      succeeded = true;
+    } catch (e) {}
+
+    if (!succeeded) {
+      throw new Error(`Importing ${resource} should have succeeded!`);
+    }
+  }
+}
+
+function expectImportsToFail(mm, base = MODULE_BASE) {
+  for (let m of mm) {
+    let resource = base + m;
+    let succeeded = false;
+    try {
+      ChromeUtils.import(resource);
+      succeeded = true;
+    } catch (e) {}
+
+    if (succeeded) {
+      throw new Error(`Importing ${resource} should have failed!`);
+    }
+  }
+}
+
+function run_test() {
+  expectImportsToSucceed(shared_modules);
+  expectImportsToSucceed(shared_test_modules, TEST_BASE);
+
+  if (AppConstants.platform != "android") {
+    expectImportsToSucceed(non_android_modules);
+  } else {
+    expectImportsToFail(non_android_modules);
+  }
+}
diff --git a/services/common/tests/unit/test_logmanager.js b/services/common/tests/unit/test_logmanager.js
new file mode 100644
index 0000000000..f7598a71ed
--- /dev/null
+++ b/services/common/tests/unit/test_logmanager.js
@@ -0,0 +1,321 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+// NOTE: The sync test_errorhandler_* tests have quite good coverage for
+// other aspects of this.
+
+const { LogManager } = ChromeUtils.importESModule(
+  "resource://services-common/logmanager.sys.mjs"
+);
+const { FileUtils } = ChromeUtils.importESModule(
+  "resource://gre/modules/FileUtils.sys.mjs"
+);
+
+// Returns an array of [consoleAppender, dumpAppender, [fileAppenders]] for
+// the specified log.  Note that fileAppenders will usually have length=1
+function getAppenders(log) {
+  let capps = log.appenders.filter(app => app instanceof Log.ConsoleAppender);
+  equal(capps.length, 1, "should only have one console appender");
+  let dapps = log.appenders.filter(app => app instanceof Log.DumpAppender);
+  equal(dapps.length, 1, "should only have one dump appender");
+  let fapps = log.appenders.filter(
+    app => app instanceof LogManager.StorageStreamAppender
+  );
+  return [capps[0], dapps[0], fapps];
+}
+
+// Test that the correct thing happens when no prefs exist for the log manager.
+add_task(async function test_noPrefs() {
+  // tell the log manager to init with a pref branch that doesn't exist.
+  let lm = new LogManager("no-such-branch.", ["TestLog"], "test");
+
+  let log = Log.repository.getLogger("TestLog");
+  let [capp, dapp, fapps] = getAppenders(log);
+  // The console appender gets "Fatal" while the "dump" appender gets "Error" levels
+  equal(capp.level, Log.Level.Fatal);
+  equal(dapp.level, Log.Level.Error);
+  // and the file (stream) appender gets Debug by default
+  equal(fapps.length, 1, "only 1 file appender");
+  equal(fapps[0].level, Log.Level.Debug);
+  lm.finalize();
+});
+
+// Test that changes to the prefs used by the log manager are updated dynamically.
+add_task(async function test_PrefChanges() {
+  Services.prefs.setCharPref("log-manager.test.log.appender.console", "Trace");
+  Services.prefs.setCharPref("log-manager.test.log.appender.dump", "Trace");
+  Services.prefs.setCharPref(
+    "log-manager.test.log.appender.file.level",
+    "Trace"
+  );
+  let lm = new LogManager("log-manager.test.", ["TestLog2"], "test");
+
+  let log = Log.repository.getLogger("TestLog2");
+  let [capp, dapp, [fapp]] = getAppenders(log);
+  equal(capp.level, Log.Level.Trace);
+  equal(dapp.level, Log.Level.Trace);
+  equal(fapp.level, Log.Level.Trace);
+  // adjust the prefs and they should magically be reflected in the appenders.
+  Services.prefs.setCharPref("log-manager.test.log.appender.console", "Debug");
+  Services.prefs.setCharPref("log-manager.test.log.appender.dump", "Debug");
+  Services.prefs.setCharPref(
+    "log-manager.test.log.appender.file.level",
+    "Debug"
+  );
+  equal(capp.level, Log.Level.Debug);
+  equal(dapp.level, Log.Level.Debug);
+  equal(fapp.level, Log.Level.Debug);
+  // and invalid values should cause them to fallback to their defaults.
+  Services.prefs.setCharPref("log-manager.test.log.appender.console", "xxx");
+  Services.prefs.setCharPref("log-manager.test.log.appender.dump", "xxx");
+  Services.prefs.setCharPref("log-manager.test.log.appender.file.level", "xxx");
+  equal(capp.level, Log.Level.Fatal);
+  equal(dapp.level, Log.Level.Error);
+  equal(fapp.level, Log.Level.Debug);
+  lm.finalize();
+});
+
+// Test that the same log used by multiple log managers does the right thing.
+add_task(async function test_SharedLogs() {
+  // create the prefs for the first instance.
+  Services.prefs.setCharPref(
+    "log-manager-1.test.log.appender.console",
+    "Trace"
+  );
+  Services.prefs.setCharPref("log-manager-1.test.log.appender.dump", "Trace");
+  Services.prefs.setCharPref(
+    "log-manager-1.test.log.appender.file.level",
+    "Trace"
+  );
+  let lm1 = new LogManager("log-manager-1.test.", ["TestLog3"], "test");
+
+  // and the second.
+  Services.prefs.setCharPref(
+    "log-manager-2.test.log.appender.console",
+    "Debug"
+  );
+  Services.prefs.setCharPref("log-manager-2.test.log.appender.dump", "Debug");
+  Services.prefs.setCharPref(
+    "log-manager-2.test.log.appender.file.level",
+    "Debug"
+  );
+  let lm2 = new LogManager("log-manager-2.test.", ["TestLog3"], "test");
+
+  let log = Log.repository.getLogger("TestLog3");
+  let [capp, dapp] = getAppenders(log);
+
+  // console and dump appenders should be "trace" as it is more verbose than
+  // "debug"
+  equal(capp.level, Log.Level.Trace);
+  equal(dapp.level, Log.Level.Trace);
+
+  // Set the prefs on the -1 branch to "Error" - it should then end up with
+  // "Debug" from the -2 branch.
+  Services.prefs.setCharPref(
+    "log-manager-1.test.log.appender.console",
+    "Error"
+  );
+  Services.prefs.setCharPref("log-manager-1.test.log.appender.dump", "Error");
+  Services.prefs.setCharPref(
+    "log-manager-1.test.log.appender.file.level",
+    "Error"
+  );
+
+  equal(capp.level, Log.Level.Debug);
+  equal(dapp.level, Log.Level.Debug);
+
+  lm1.finalize();
+  lm2.finalize();
+});
+
+// A little helper to test what log files exist.  We expect exactly zero (if
+// prefix is null) or exactly one with the specified prefix.
+function checkLogFile(prefix) {
+  let logsdir = FileUtils.getDir("ProfD", ["weave", "logs"], true);
+  let entries = logsdir.directoryEntries;
+  if (!prefix) {
+    // expecting no files.
+    ok(!entries.hasMoreElements());
+  } else {
+    // expecting 1 file.
+    ok(entries.hasMoreElements());
+    let logfile = entries.getNext().QueryInterface(Ci.nsIFile);
+    equal(logfile.leafName.slice(-4), ".txt");
+    ok(logfile.leafName.startsWith(prefix + "-test-"), logfile.leafName);
+    // and remove it ready for the next check.
+    logfile.remove(false);
+  }
+}
+
+// Test that we correctly write error logs by default
+add_task(async function test_logFileErrorDefault() {
+  let lm = new LogManager("log-manager.test.", ["TestLog2"], "test");
+
+  let log = Log.repository.getLogger("TestLog2");
+  log.error("an error message");
+  await lm.resetFileLog(lm.REASON_ERROR);
+  // One error log file exists.
+  checkLogFile("error");
+
+  lm.finalize();
+});
+
+// Test that we correctly write success logs.
+add_task(async function test_logFileSuccess() {
+  Services.prefs.setBoolPref(
+    "log-manager.test.log.appender.file.logOnError",
+    false
+  );
+  Services.prefs.setBoolPref(
+    "log-manager.test.log.appender.file.logOnSuccess",
+    false
+  );
+
+  let lm = new LogManager("log-manager.test.", ["TestLog2"], "test");
+
+  let log = Log.repository.getLogger("TestLog2");
+  log.info("an info message");
+  await lm.resetFileLog();
+  // Zero log files exist.
+  checkLogFile(null);
+
+  // Reset logOnSuccess and do it again - log should appear.
+  Services.prefs.setBoolPref(
+    "log-manager.test.log.appender.file.logOnSuccess",
+    true
+  );
+  log.info("an info message");
+  await lm.resetFileLog();
+
+  checkLogFile("success");
+
+  // Now test with no "reason" specified and no "error" record.
+  log.info("an info message");
+  await lm.resetFileLog();
+  // should get a "success" entry.
+  checkLogFile("success");
+
+  // With no "reason" and an error record - should get no success log.
+  log.error("an error message");
+  await lm.resetFileLog();
+  // should get no entry
+  checkLogFile(null);
+
+  // And finally now with no error, to ensure that the fact we had an error
+  // previously doesn't persist after the .resetFileLog call.
+  log.info("an info message");
+  await lm.resetFileLog();
+  checkLogFile("success");
+
+  lm.finalize();
+});
+
+// Test that we correctly write error logs.
+add_task(async function test_logFileError() {
+  Services.prefs.setBoolPref(
+    "log-manager.test.log.appender.file.logOnError",
+    false
+  );
+  Services.prefs.setBoolPref(
+    "log-manager.test.log.appender.file.logOnSuccess",
+    false
+  );
+
+  let lm = new LogManager("log-manager.test.", ["TestLog2"], "test");
+
+  let log = Log.repository.getLogger("TestLog2");
+  log.info("an info message");
+  let reason = await lm.resetFileLog();
+  Assert.equal(reason, null, "null returned when no file created.");
+  // Zero log files exist.
+  checkLogFile(null);
+
+  // Reset logOnSuccess - success logs should appear if no error records.
+  Services.prefs.setBoolPref(
+    "log-manager.test.log.appender.file.logOnSuccess",
+    true
+  );
+  log.info("an info message");
+  reason = await lm.resetFileLog();
+  Assert.equal(reason, lm.SUCCESS_LOG_WRITTEN);
+  checkLogFile("success");
+
+  // Set logOnError and unset logOnSuccess - error logs should appear.
+  Services.prefs.setBoolPref(
+    "log-manager.test.log.appender.file.logOnSuccess",
+    false
+  );
+  Services.prefs.setBoolPref(
+    "log-manager.test.log.appender.file.logOnError",
+    true
+  );
+  log.error("an error message");
+  reason = await lm.resetFileLog();
+  Assert.equal(reason, lm.ERROR_LOG_WRITTEN);
+  checkLogFile("error");
+
+  // Now test with no "error" record.
+  log.info("an info message");
+  reason = await lm.resetFileLog();
+  // should get no file
+  Assert.equal(reason, null);
+  checkLogFile(null);
+
+  // With an error record we should get an error log.
+  log.error("an error message");
+  reason = await lm.resetFileLog();
+  // should get en error log
+  Assert.equal(reason, lm.ERROR_LOG_WRITTEN);
+  checkLogFile("error");
+
+  // And finally now with success, to ensure that the fact we had an error
+  // previously doesn't persist after the .resetFileLog call.
+  log.info("an info message");
+  await lm.resetFileLog();
+  checkLogFile(null);
+
+  lm.finalize();
+});
+
+function countLogFiles() {
+  let logsdir = FileUtils.getDir("ProfD", ["weave", "logs"], true);
+  let count = 0;
+  for (let entry of logsdir.directoryEntries) {
+    void entry;
+    count += 1;
+  }
+  return count;
+}
+
+// Test that removeAllLogs removes all log files.
+add_task(async function test_logFileError() {
+  Services.prefs.setBoolPref(
+    "log-manager.test.log.appender.file.logOnError",
+    true
+  );
+  Services.prefs.setBoolPref(
+    "log-manager.test.log.appender.file.logOnSuccess",
+    true
+  );
+
+  let lm = new LogManager("log-manager.test.", ["TestLog2"], "test");
+
+  let log = Log.repository.getLogger("TestLog2");
+  log.info("an info message");
+  let reason = await lm.resetFileLog();
+  Assert.equal(reason, lm.SUCCESS_LOG_WRITTEN, "success log was written.");
+
+  log.error("an error message");
+  reason = await lm.resetFileLog();
+  Assert.equal(reason, lm.ERROR_LOG_WRITTEN);
+
+  Assert.equal(countLogFiles(), 2, "expect 2 log files");
+  await lm.removeAllLogs();
+  Assert.equal(
+    countLogFiles(),
+    0,
+    "should be no log files after removing them"
+  );
+
+  lm.finalize();
+});
diff --git a/services/common/tests/unit/test_observers.js b/services/common/tests/unit/test_observers.js
new file mode 100644
index 0000000000..b0fce95e0b
--- /dev/null
+++ b/services/common/tests/unit/test_observers.js
@@ -0,0 +1,82 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { Observers } = ChromeUtils.importESModule(
+  "resource://services-common/observers.sys.mjs"
+);
+
+var gSubject = {};
+
+add_test(function test_function_observer() {
+  let foo = false;
+
+  let onFoo = function (subject, data) {
+    foo = !foo;
+    Assert.equal(subject, gSubject);
+    Assert.equal(data, "some data");
+  };
+
+  Observers.add("foo", onFoo);
+  Observers.notify("foo", gSubject, "some data");
+
+  // The observer was notified after being added.
+  Assert.ok(foo);
+
+  Observers.remove("foo", onFoo);
+  Observers.notify("foo");
+
+  // The observer was not notified after being removed.
+  Assert.ok(foo);
+
+  run_next_test();
+});
+
+add_test(function test_method_observer() {
+  let obj = {
+    foo: false,
+    onFoo(subject, data) {
+      this.foo = !this.foo;
+      Assert.equal(subject, gSubject);
+      Assert.equal(data, "some data");
+    },
+  };
+
+  // The observer is notified after being added.
+  Observers.add("foo", obj.onFoo, obj);
+  Observers.notify("foo", gSubject, "some data");
+  Assert.ok(obj.foo);
+
+  // The observer is not notified after being removed.
+  Observers.remove("foo", obj.onFoo, obj);
+  Observers.notify("foo");
+  Assert.ok(obj.foo);
+
+  run_next_test();
+});
+
+add_test(function test_object_observer() {
+  let obj = {
+    foo: false,
+    observe(subject, topic, data) {
+      this.foo = !this.foo;
+
+      Assert.equal(subject, gSubject);
+      Assert.equal(topic, "foo");
+      Assert.equal(data, "some data");
+    },
+  };
+
+  Observers.add("foo", obj);
+  Observers.notify("foo", gSubject, "some data");
+
+  // The observer is notified after being added.
+  Assert.ok(obj.foo);
+
+  Observers.remove("foo", obj);
+  Observers.notify("foo");
+
+  // The observer is not notified after being removed.
+  Assert.ok(obj.foo);
+
+  run_next_test();
+});
diff --git a/services/common/tests/unit/test_restrequest.js b/services/common/tests/unit/test_restrequest.js
new file mode 100644
index 0000000000..9ae5e9429a
--- /dev/null
+++ b/services/common/tests/unit/test_restrequest.js
@@ -0,0 +1,860 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const { RESTRequest } = ChromeUtils.importESModule(
+  "resource://services-common/rest.sys.mjs"
+);
+
+function run_test() {
+  Log.repository.getLogger("Services.Common.RESTRequest").level =
+    Log.Level.Trace;
+  initTestLogging("Trace");
+
+  run_next_test();
+}
+
+/**
+ * Initializing a RESTRequest with an invalid URI throws
+ * NS_ERROR_MALFORMED_URI.
+ */
+add_test(function test_invalid_uri() {
+  do_check_throws(function () {
+    new RESTRequest("an invalid URI");
+  }, Cr.NS_ERROR_MALFORMED_URI);
+  run_next_test();
+});
+
+/**
+ * Verify initial values for attributes.
+ */
+add_test(function test_attributes() {
+  let uri = "http://foo.com/bar/baz";
+  let request = new RESTRequest(uri);
+
+  Assert.ok(request.uri instanceof Ci.nsIURI);
+  Assert.equal(request.uri.spec, uri);
+  Assert.equal(request.response, null);
+  Assert.equal(request.status, request.NOT_SENT);
+  let expectedLoadFlags =
+    Ci.nsIRequest.LOAD_BYPASS_CACHE |
+    Ci.nsIRequest.INHIBIT_CACHING |
+    Ci.nsIRequest.LOAD_ANONYMOUS;
+  Assert.equal(request.loadFlags, expectedLoadFlags);
+
+  run_next_test();
+});
+
+/**
+ * Verify that a proxy auth redirect doesn't break us. This has to be the first
+ * request made in the file!
+ */
+add_task(async function test_proxy_auth_redirect() {
+  let pacFetched = false;
+  function pacHandler(metadata, response) {
+    pacFetched = true;
+    let body = 'function FindProxyForURL(url, host) { return "DIRECT"; }';
+    response.setStatusLine(metadata.httpVersion, 200, "OK");
+    response.setHeader(
+      "Content-Type",
+      "application/x-ns-proxy-autoconfig",
+      false
+    );
+    response.bodyOutputStream.write(body, body.length);
+  }
+
+  let fetched = false;
+  function original(metadata, response) {
+    fetched = true;
+    let body = "TADA!";
+    response.setStatusLine(metadata.httpVersion, 200, "OK");
+    response.bodyOutputStream.write(body, body.length);
+  }
+
+  let server = httpd_setup({
+    "/original": original,
+    "/pac3": pacHandler,
+  });
+  PACSystemSettings.PACURI = server.baseURI + "/pac3";
+  installFakePAC();
+
+  let req = new RESTRequest(server.baseURI + "/original");
+  await req.get();
+
+  Assert.ok(pacFetched);
+  Assert.ok(fetched);
+
+  Assert.ok(req.response.success);
+  Assert.equal("TADA!", req.response.body);
+  uninstallFakePAC();
+  await promiseStopServer(server);
+});
+
+/**
+ * Ensure that failures that cause asyncOpen to throw
+ * result in callbacks being invoked.
+ * Bug 826086.
+ */
+add_task(async function test_forbidden_port() {
+  let request = new RESTRequest("http://localhost:6000/");
+
+  await Assert.rejects(
+    request.get(),
+    error => error.result == Cr.NS_ERROR_PORT_ACCESS_NOT_ALLOWED
+  );
+});
+
+/**
+ * Demonstrate API short-hand: create a request and dispatch it immediately.
+ */
+add_task(async function test_simple_get() {
+  let handler = httpd_handler(200, "OK", "Huzzah!");
+  let server = httpd_setup({ "/resource": handler });
+  let request = new RESTRequest(server.baseURI + "/resource");
+  let promiseResponse = request.get();
+
+  Assert.equal(request.status, request.SENT);
+  Assert.equal(request.method, "GET");
+
+  let response = await promiseResponse;
+  Assert.equal(response, request.response);
+
+  Assert.equal(request.status, request.COMPLETED);
+  Assert.ok(response.success);
+  Assert.equal(response.status, 200);
+  Assert.equal(response.body, "Huzzah!");
+  await promiseStopServer(server);
+});
+
+/**
+ * Test HTTP GET with all bells and whistles.
+ */
+add_task(async function test_get() {
+  let handler = httpd_handler(200, "OK", "Huzzah!");
+  let server = httpd_setup({ "/resource": handler });
+
+  let request = new RESTRequest(server.baseURI + "/resource");
+  Assert.equal(request.status, request.NOT_SENT);
+
+  let promiseResponse = request.get();
+
+  Assert.equal(request.status, request.SENT);
+  Assert.equal(request.method, "GET");
+
+  Assert.ok(!!(request.channel.loadFlags & Ci.nsIRequest.LOAD_BYPASS_CACHE));
+  Assert.ok(!!(request.channel.loadFlags & Ci.nsIRequest.INHIBIT_CACHING));
+
+  let response = await promiseResponse;
+
+  Assert.equal(response, request.response);
+  Assert.equal(request.status, request.COMPLETED);
+  Assert.ok(request.response.success);
+  Assert.equal(request.response.status, 200);
+  Assert.equal(request.response.body, "Huzzah!");
+  Assert.equal(handler.request.method, "GET");
+
+  await Assert.rejects(request.get(), /Request has already been sent/);
+
+  await promiseStopServer(server);
+});
+
+/**
+ * Test HTTP GET with UTF-8 content, and custom Content-Type.
+ */
+add_task(async function test_get_utf8() {
+  let response = "Hello World or Καλημέρα κόσμε or こんにちは 世界 😺";
+
+  let contentType = "text/plain";
+  let charset = true;
+  let charsetSuffix = "; charset=UTF-8";
+
+  let server = httpd_setup({
+    "/resource": function (req, res) {
+      res.setStatusLine(req.httpVersion, 200, "OK");
+      res.setHeader(
+        "Content-Type",
+        contentType + (charset ? charsetSuffix : "")
+      );
+
+      let converter = Cc[
+        "@mozilla.org/intl/converter-output-stream;1"
+      ].createInstance(Ci.nsIConverterOutputStream);
+      converter.init(res.bodyOutputStream, "UTF-8");
+      converter.writeString(response);
+      converter.close();
+    },
+  });
+
+  // Check if charset in Content-Type is propertly interpreted.
+  let request1 = new RESTRequest(server.baseURI + "/resource");
+  await request1.get();
+
+  Assert.equal(request1.response.status, 200);
+  Assert.equal(request1.response.body, response);
+  Assert.equal(
+    request1.response.headers["content-type"],
+    contentType + charsetSuffix
+  );
+
+  // Check that we default to UTF-8 if Content-Type doesn't have a charset
+  charset = false;
+  let request2 = new RESTRequest(server.baseURI + "/resource");
+  await request2.get();
+  Assert.equal(request2.response.status, 200);
+  Assert.equal(request2.response.body, response);
+  Assert.equal(request2.response.headers["content-type"], contentType);
+  Assert.equal(request2.response.charset, "utf-8");
+
+  let request3 = new RESTRequest(server.baseURI + "/resource");
+
+  // With the test server we tend to get onDataAvailable in chunks of 8192 (in
+  // real network requests there doesn't appear to be any pattern to the size of
+  // the data `onDataAvailable` is called with), the smiling cat emoji encodes as
+  // 4 bytes, and so when utf8 encoded, the `"a" + "😺".repeat(2048)` will not be
+  // aligned onto a codepoint.
+  //
+  // Since 8192 isn't guaranteed and could easily change, the following string is
+  // a) very long, and b) misaligned on roughly 3/4 of the bytes, as a safety
+  // measure.
+  response = ("a" + "😺".repeat(2048)).repeat(10);
+
+  await request3.get();
+
+  Assert.equal(request3.response.status, 200);
+
+  // Make sure it came through ok, despite the misalignment.
+  Assert.equal(request3.response.body, response);
+
+  await promiseStopServer(server);
+});
+
+/**
+ * Test HTTP POST data is encoded as UTF-8 by default.
+ */
+add_task(async function test_post_utf8() {
+  // We setup a handler that responds with exactly what it received.
+  // Given we've already tested above that responses are correctly utf-8
+  // decoded we can surmise that the correct response coming back means the
+  // input must also have been encoded.
+  let server = httpd_setup({
+    "/echo": function (req, res) {
+      res.setStatusLine(req.httpVersion, 200, "OK");
+      res.setHeader("Content-Type", req.getHeader("content-type"));
+      // Get the body as bytes and write them back without touching them
+      let sis = Cc["@mozilla.org/scriptableinputstream;1"].createInstance(
+        Ci.nsIScriptableInputStream
+      );
+      sis.init(req.bodyInputStream);
+      let body = sis.read(sis.available());
+      sis.close();
+      res.write(body);
+    },
+  });
+
+  let data = {
+    copyright: "©",
+    // See the comment in test_get_utf8 about this string.
+    long: ("a" + "😺".repeat(2048)).repeat(10),
+  };
+  let request1 = new RESTRequest(server.baseURI + "/echo");
+  await request1.post(data);
+
+  Assert.equal(request1.response.status, 200);
+  deepEqual(JSON.parse(request1.response.body), data);
+  Assert.equal(
+    request1.response.headers["content-type"],
+    "application/json; charset=utf-8"
+  );
+
+  await promiseStopServer(server);
+});
+
+/**
+ * Test more variations of charset handling.
+ */
+add_task(async function test_charsets() {
+  let response = "Hello World, I can't speak Russian";
+
+  let contentType = "text/plain";
+  let charset = true;
+  let charsetSuffix = "; charset=us-ascii";
+
+  let server = httpd_setup({
+    "/resource": function (req, res) {
+      res.setStatusLine(req.httpVersion, 200, "OK");
+      res.setHeader(
+        "Content-Type",
+        contentType + (charset ? charsetSuffix : "")
+      );
+
+      let converter = Cc[
+        "@mozilla.org/intl/converter-output-stream;1"
+      ].createInstance(Ci.nsIConverterOutputStream);
+      converter.init(res.bodyOutputStream, "us-ascii");
+      converter.writeString(response);
+      converter.close();
+    },
+  });
+
+  // Check that provided charset overrides hint.
+  let request1 = new RESTRequest(server.baseURI + "/resource");
+  request1.charset = "not-a-charset";
+  await request1.get();
+  Assert.equal(request1.response.status, 200);
+  Assert.equal(request1.response.body, response);
+  Assert.equal(
+    request1.response.headers["content-type"],
+    contentType + charsetSuffix
+  );
+  Assert.equal(request1.response.charset, "us-ascii");
+
+  // Check that hint is used if Content-Type doesn't have a charset.
+  charset = false;
+  let request2 = new RESTRequest(server.baseURI + "/resource");
+  request2.charset = "us-ascii";
+  await request2.get();
+
+  Assert.equal(request2.response.status, 200);
+  Assert.equal(request2.response.body, response);
+  Assert.equal(request2.response.headers["content-type"], contentType);
+  Assert.equal(request2.response.charset, "us-ascii");
+
+  await promiseStopServer(server);
+});
+
+/**
+ * Used for testing PATCH/PUT/POST methods.
+ */
+async function check_posting_data(method) {
+  let funcName = method.toLowerCase();
+  let handler = httpd_handler(200, "OK", "Got it!");
+  let server = httpd_setup({ "/resource": handler });
+
+  let request = new RESTRequest(server.baseURI + "/resource");
+  Assert.equal(request.status, request.NOT_SENT);
+  let responsePromise = request[funcName]("Hullo?");
+  Assert.equal(request.status, request.SENT);
+  Assert.equal(request.method, method);
+
+  let response = await responsePromise;
+
+  Assert.equal(response, request.response);
+
+  Assert.equal(request.status, request.COMPLETED);
+  Assert.ok(request.response.success);
+  Assert.equal(request.response.status, 200);
+  Assert.equal(request.response.body, "Got it!");
+
+  Assert.equal(handler.request.method, method);
+  Assert.equal(handler.request.body, "Hullo?");
+  Assert.equal(handler.request.getHeader("Content-Type"), "text/plain");
+
+  await Assert.rejects(
+    request[funcName]("Hai!"),
+    /Request has already been sent/
+  );
+
+  await promiseStopServer(server);
+}
+
+/**
+ * Test HTTP PATCH with a simple string argument and default Content-Type.
+ */
+add_task(async function test_patch() {
+  await check_posting_data("PATCH");
+});
+
+/**
+ * Test HTTP PUT with a simple string argument and default Content-Type.
+ */
+add_task(async function test_put() {
+  await check_posting_data("PUT");
+});
+
+/**
+ * Test HTTP POST with a simple string argument and default Content-Type.
+ */
+add_task(async function test_post() {
+  await check_posting_data("POST");
+});
+
+/**
+ * Test HTTP DELETE.
+ */
+add_task(async function test_delete() {
+  let handler = httpd_handler(200, "OK", "Got it!");
+  let server = httpd_setup({ "/resource": handler });
+
+  let request = new RESTRequest(server.baseURI + "/resource");
+  Assert.equal(request.status, request.NOT_SENT);
+  let responsePromise = request.delete();
+  Assert.equal(request.status, request.SENT);
+  Assert.equal(request.method, "DELETE");
+
+  let response = await responsePromise;
+  Assert.equal(response, request.response);
+
+  Assert.equal(request.status, request.COMPLETED);
+  Assert.ok(request.response.success);
+  Assert.equal(request.response.status, 200);
+  Assert.equal(request.response.body, "Got it!");
+  Assert.equal(handler.request.method, "DELETE");
+
+  await Assert.rejects(request.delete(), /Request has already been sent/);
+
+  await promiseStopServer(server);
+});
+
+/**
+ * Test an HTTP response with a non-200 status code.
+ */
+add_task(async function test_get_404() {
+  let handler = httpd_handler(404, "Not Found", "Cannae find it!");
+  let server = httpd_setup({ "/resource": handler });
+
+  let request = new RESTRequest(server.baseURI + "/resource");
+  await request.get();
+
+  Assert.equal(request.status, request.COMPLETED);
+  Assert.ok(!request.response.success);
+  Assert.equal(request.response.status, 404);
+  Assert.equal(request.response.body, "Cannae find it!");
+
+  await promiseStopServer(server);
+});
+
+/**
+ * The 'data' argument to PUT, if not a string already, is automatically
+ * stringified as JSON.
+ */
+add_task(async function test_put_json() {
+  let handler = httpd_handler(200, "OK");
+  let server = httpd_setup({ "/resource": handler });
+
+  let sample_data = {
+    some: "sample_data",
+    injson: "format",
+    number: 42,
+  };
+  let request = new RESTRequest(server.baseURI + "/resource");
+  await request.put(sample_data);
+
+  Assert.equal(request.status, request.COMPLETED);
+  Assert.ok(request.response.success);
+  Assert.equal(request.response.status, 200);
+  Assert.equal(request.response.body, "");
+
+  Assert.equal(handler.request.method, "PUT");
+  Assert.equal(handler.request.body, JSON.stringify(sample_data));
+  Assert.equal(
+    handler.request.getHeader("Content-Type"),
+    "application/json; charset=utf-8"
+  );
+
+  await promiseStopServer(server);
+});
+
+/**
+ * The 'data' argument to POST, if not a string already, is automatically
+ * stringified as JSON.
+ */
+add_task(async function test_post_json() {
+  let handler = httpd_handler(200, "OK");
+  let server = httpd_setup({ "/resource": handler });
+
+  let sample_data = {
+    some: "sample_data",
+    injson: "format",
+    number: 42,
+  };
+  let request = new RESTRequest(server.baseURI + "/resource");
+  await request.post(sample_data);
+
+  Assert.equal(request.status, request.COMPLETED);
+  Assert.ok(request.response.success);
+  Assert.equal(request.response.status, 200);
+  Assert.equal(request.response.body, "");
+
+  Assert.equal(handler.request.method, "POST");
+  Assert.equal(handler.request.body, JSON.stringify(sample_data));
+  Assert.equal(
+    handler.request.getHeader("Content-Type"),
+    "application/json; charset=utf-8"
+  );
+
+  await promiseStopServer(server);
+});
+
+/**
+ * The content-type will be text/plain without a charset if the 'data' argument
+ * to POST is already a string.
+ */
+add_task(async function test_post_json() {
+  let handler = httpd_handler(200, "OK");
+  let server = httpd_setup({ "/resource": handler });
+
+  let sample_data = "hello";
+  let request = new RESTRequest(server.baseURI + "/resource");
+  await request.post(sample_data);
+  Assert.equal(request.status, request.COMPLETED);
+  Assert.ok(request.response.success);
+  Assert.equal(request.response.status, 200);
+  Assert.equal(request.response.body, "");
+
+  Assert.equal(handler.request.method, "POST");
+  Assert.equal(handler.request.body, sample_data);
+  Assert.equal(handler.request.getHeader("Content-Type"), "text/plain");
+
+  await promiseStopServer(server);
+});
+
+/**
+ * HTTP PUT with a custom Content-Type header.
+ */
+add_task(async function test_put_override_content_type() {
+  let handler = httpd_handler(200, "OK");
+  let server = httpd_setup({ "/resource": handler });
+
+  let request = new RESTRequest(server.baseURI + "/resource");
+  request.setHeader("Content-Type", "application/lolcat");
+  await request.put("O HAI!!1!");
+
+  Assert.equal(request.status, request.COMPLETED);
+  Assert.ok(request.response.success);
+  Assert.equal(request.response.status, 200);
+  Assert.equal(request.response.body, "");
+
+  Assert.equal(handler.request.method, "PUT");
+  Assert.equal(handler.request.body, "O HAI!!1!");
+  Assert.equal(handler.request.getHeader("Content-Type"), "application/lolcat");
+
+  await promiseStopServer(server);
+});
+
+/**
+ * HTTP POST with a custom Content-Type header.
+ */
+add_task(async function test_post_override_content_type() {
+  let handler = httpd_handler(200, "OK");
+  let server = httpd_setup({ "/resource": handler });
+
+  let request = new RESTRequest(server.baseURI + "/resource");
+  request.setHeader("Content-Type", "application/lolcat");
+  await request.post("O HAI!!1!");
+
+  Assert.equal(request.status, request.COMPLETED);
+  Assert.ok(request.response.success);
+  Assert.equal(request.response.status, 200);
+  Assert.equal(request.response.body, "");
+
+  Assert.equal(handler.request.method, "POST");
+  Assert.equal(handler.request.body, "O HAI!!1!");
+  Assert.equal(handler.request.getHeader("Content-Type"), "application/lolcat");
+
+  await promiseStopServer(server);
+});
+
+/**
+ * No special headers are sent by default on a GET request.
+ */
+add_task(async function test_get_no_headers() {
+  let handler = httpd_handler(200, "OK");
+  let server = httpd_setup({ "/resource": handler });
+
+  let ignore_headers = [
+    "host",
+    "user-agent",
+    "accept",
+    "accept-language",
+    "accept-encoding",
+    "accept-charset",
+    "keep-alive",
+    "connection",
+    "pragma",
+    "cache-control",
+    "content-length",
+    "sec-fetch-dest",
+    "sec-fetch-mode",
+    "sec-fetch-site",
+    "sec-fetch-user",
+  ];
+  let request = new RESTRequest(server.baseURI + "/resource");
+  await request.get();
+
+  Assert.equal(request.response.status, 200);
+  Assert.equal(request.response.body, "");
+
+  let server_headers = handler.request.headers;
+  while (server_headers.hasMoreElements()) {
+    let header = server_headers.getNext().toString();
+    if (!ignore_headers.includes(header)) {
+      do_throw("Got unexpected header!");
+    }
+  }
+
+  await promiseStopServer(server);
+});
+
+/**
+ * Client includes default Accept header in API requests
+ */
+add_task(async function test_default_accept_headers() {
+  let handler = httpd_handler(200, "OK");
+  let server = httpd_setup({ "/resource": handler });
+
+  let request = new RESTRequest(server.baseURI + "/resource");
+  await request.get();
+
+  Assert.equal(request.response.status, 200);
+  Assert.equal(request.response.body, "");
+
+  let accept_header = handler.request.getHeader("accept");
+
+  Assert.ok(!accept_header.includes("text/html"));
+  Assert.ok(!accept_header.includes("application/xhtml+xml"));
+  Assert.ok(!accept_header.includes("applcation/xml"));
+
+  Assert.ok(
+    accept_header.includes("application/json") ||
+      accept_header.includes("application/newlines")
+  );
+
+  await promiseStopServer(server);
+});
+
+/**
+ * Test changing the URI after having created the request.
+ */
+add_task(async function test_changing_uri() {
+  let handler = httpd_handler(200, "OK");
+  let server = httpd_setup({ "/resource": handler });
+
+  let request = new RESTRequest("http://localhost:1234/the-wrong-resource");
+  request.uri = CommonUtils.makeURI(server.baseURI + "/resource");
+  let response = await request.get();
+  Assert.equal(response.status, 200);
+  await promiseStopServer(server);
+});
+
+/**
+ * Test setting HTTP request headers.
+ */
+add_task(async function test_request_setHeader() {
+  let handler = httpd_handler(200, "OK");
+  let server = httpd_setup({ "/resource": handler });
+
+  let request = new RESTRequest(server.baseURI + "/resource");
+
+  request.setHeader("X-What-Is-Weave", "awesome");
+  request.setHeader("X-WHAT-is-Weave", "more awesomer");
+  request.setHeader("Another-Header", "Hello World");
+  await request.get();
+
+  Assert.equal(request.response.status, 200);
+  Assert.equal(request.response.body, "");
+
+  Assert.equal(handler.request.getHeader("X-What-Is-Weave"), "more awesomer");
+  Assert.equal(handler.request.getHeader("another-header"), "Hello World");
+
+  await promiseStopServer(server);
+});
+
+/**
+ * Test receiving HTTP response headers.
+ */
+add_task(async function test_response_headers() {
+  function handler(request, response) {
+    response.setHeader("X-What-Is-Weave", "awesome");
+    response.setHeader("Another-Header", "Hello World");
+    response.setStatusLine(request.httpVersion, 200, "OK");
+  }
+  let server = httpd_setup({ "/resource": handler });
+  let request = new RESTRequest(server.baseURI + "/resource");
+  await request.get();
+
+  Assert.equal(request.response.status, 200);
+  Assert.equal(request.response.body, "");
+
+  Assert.equal(request.response.headers["x-what-is-weave"], "awesome");
+  Assert.equal(request.response.headers["another-header"], "Hello World");
+
+  await promiseStopServer(server);
+});
+
+/**
+ * The onComplete() handler gets called in case of any network errors
+ * (e.g. NS_ERROR_CONNECTION_REFUSED).
+ */
+add_task(async function test_connection_refused() {
+  let request = new RESTRequest("http://localhost:1234/resource");
+
+  // Fail the test if we resolve, return the error if we reject
+  await Assert.rejects(
+    request.get(),
+    error =>
+      error.result == Cr.NS_ERROR_CONNECTION_REFUSED &&
+      error.message == "NS_ERROR_CONNECTION_REFUSED"
+  );
+
+  Assert.equal(request.status, request.COMPLETED);
+});
+
+/**
+ * Abort a request that just sent off.
+ */
+add_task(async function test_abort() {
+  function handler() {
+    do_throw("Shouldn't have gotten here!");
+  }
+  let server = httpd_setup({ "/resource": handler });
+
+  let request = new RESTRequest(server.baseURI + "/resource");
+
+  // Aborting a request that hasn't been sent yet is pointless and will throw.
+  do_check_throws(function () {
+    request.abort();
+  });
+
+  let responsePromise = request.get();
+  request.abort();
+
+  // Aborting an already aborted request is pointless and will throw.
+  do_check_throws(function () {
+    request.abort();
+  });
+
+  Assert.equal(request.status, request.ABORTED);
+
+  await Assert.rejects(responsePromise, /NS_BINDING_ABORTED/);
+
+  await promiseStopServer(server);
+});
+
+/**
+ * A non-zero 'timeout' property specifies the amount of seconds to wait after
+ * channel activity until the request is automatically canceled.
+ */
+add_task(async function test_timeout() {
+  let server = new HttpServer();
+  let server_connection;
+  server._handler.handleResponse = function (connection) {
+    // This is a handler that doesn't do anything, just keeps the connection
+    // open, thereby mimicking a timing out connection. We keep a reference to
+    // the open connection for later so it can be properly disposed of. That's
+    // why you really only want to make one HTTP request to this server ever.
+    server_connection = connection;
+  };
+  server.start();
+  let identity = server.identity;
+  let uri =
+    identity.primaryScheme +
+    "://" +
+    identity.primaryHost +
+    ":" +
+    identity.primaryPort;
+
+  let request = new RESTRequest(uri + "/resource");
+  request.timeout = 0.1; // 100 milliseconds
+
+  await Assert.rejects(
+    request.get(),
+    error => error.result == Cr.NS_ERROR_NET_TIMEOUT
+  );
+
+  Assert.equal(request.status, request.ABORTED);
+
+  // server_connection is undefined on the Android emulator for reasons
+  // unknown. Yet, we still get here. If this test is refactored, we should
+  // investigate the reason why the above callback is behaving differently.
+  if (server_connection) {
+    _("Closing connection.");
+    server_connection.close();
+  }
+  await promiseStopServer(server);
+});
+
+add_task(async function test_new_channel() {
+  _("Ensure a redirect to a new channel is handled properly.");
+
+  function checkUA(metadata) {
+    let ua = metadata.getHeader("User-Agent");
+    _("User-Agent is " + ua);
+    Assert.equal("foo bar", ua);
+  }
+
+  let redirectRequested = false;
+  let redirectURL;
+  function redirectHandler(metadata, response) {
+    checkUA(metadata);
+    redirectRequested = true;
+
+    let body = "Redirecting";
+    response.setStatusLine(metadata.httpVersion, 307, "TEMPORARY REDIRECT");
+    response.setHeader("Location", redirectURL);
+    response.bodyOutputStream.write(body, body.length);
+  }
+
+  let resourceRequested = false;
+  function resourceHandler(metadata, response) {
+    checkUA(metadata);
+    resourceRequested = true;
+
+    let body = "Test";
+    response.setHeader("Content-Type", "text/plain");
+    response.bodyOutputStream.write(body, body.length);
+  }
+
+  let server1 = httpd_setup({ "/redirect": redirectHandler });
+  let server2 = httpd_setup({ "/resource": resourceHandler });
+  redirectURL = server2.baseURI + "/resource";
+
+  let request = new RESTRequest(server1.baseURI + "/redirect");
+  request.setHeader("User-Agent", "foo bar");
+
+  // Swizzle in our own fakery, because this redirect is neither
+  // internal nor URI-preserving. RESTRequest's policy is to only
+  // copy headers under certain circumstances.
+  let protoMethod = request.shouldCopyOnRedirect;
+  request.shouldCopyOnRedirect = function wrapped(o, n, f) {
+    // Check the default policy.
+    Assert.ok(!protoMethod.call(this, o, n, f));
+    return true;
+  };
+
+  let response = await request.get();
+
+  Assert.equal(200, response.status);
+  Assert.equal("Test", response.body);
+  Assert.ok(redirectRequested);
+  Assert.ok(resourceRequested);
+
+  await promiseStopServer(server1);
+  await promiseStopServer(server2);
+});
+
+add_task(async function test_not_sending_cookie() {
+  function handler(metadata, response) {
+    let body = "COOKIE!";
+    response.setStatusLine(metadata.httpVersion, 200, "OK");
+    response.bodyOutputStream.write(body, body.length);
+    Assert.ok(!metadata.hasHeader("Cookie"));
+  }
+  let server = httpd_setup({ "/test": handler });
+
+  let uri = CommonUtils.makeURI(server.baseURI);
+  let channel = NetUtil.newChannel({
+    uri,
+    loadUsingSystemPrincipal: true,
+    contentPolicyType: Ci.nsIContentPolicy.TYPE_DOCUMENT,
+  });
+  Services.cookies.setCookieStringFromHttp(uri, "test=test; path=/;", channel);
+
+  let res = new RESTRequest(server.baseURI + "/test");
+  let response = await res.get();
+
+  Assert.ok(response.success);
+  Assert.equal("COOKIE!", response.body);
+
+  await promiseStopServer(server);
+});
diff --git a/services/common/tests/unit/test_storage_adapter.js b/services/common/tests/unit/test_storage_adapter.js
new file mode 100644
index 0000000000..1dda35ad12
--- /dev/null
+++ b/services/common/tests/unit/test_storage_adapter.js
@@ -0,0 +1,307 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { Sqlite } = ChromeUtils.importESModule(
+  "resource://gre/modules/Sqlite.sys.mjs"
+);
+const { FirefoxAdapter } = ChromeUtils.importESModule(
+  "resource://services-common/kinto-storage-adapter.sys.mjs"
+);
+
+// set up what we need to make storage adapters
+const kintoFilename = "kinto.sqlite";
+
+function do_get_kinto_connection() {
+  return FirefoxAdapter.openConnection({ path: kintoFilename });
+}
+
+function do_get_kinto_adapter(sqliteHandle) {
+  return new FirefoxAdapter("test", { sqliteHandle });
+}
+
+function do_get_kinto_db() {
+  let profile = do_get_profile();
+  let kintoDB = profile.clone();
+  kintoDB.append(kintoFilename);
+  return kintoDB;
+}
+
+function cleanup_kinto() {
+  add_test(function cleanup_kinto_files() {
+    let kintoDB = do_get_kinto_db();
+    // clean up the db
+    kintoDB.remove(false);
+    run_next_test();
+  });
+}
+
+function test_collection_operations() {
+  add_task(async function test_kinto_clear() {
+    let sqliteHandle = await do_get_kinto_connection();
+    let adapter = do_get_kinto_adapter(sqliteHandle);
+    await adapter.clear();
+    await sqliteHandle.close();
+  });
+
+  // test creating new records... and getting them again
+  add_task(async function test_kinto_create_new_get_existing() {
+    let sqliteHandle = await do_get_kinto_connection();
+    let adapter = do_get_kinto_adapter(sqliteHandle);
+    let record = { id: "test-id", foo: "bar" };
+    await adapter.execute(transaction => transaction.create(record));
+    let newRecord = await adapter.get("test-id");
+    // ensure the record is the same as when it was added
+    deepEqual(record, newRecord);
+    await sqliteHandle.close();
+  });
+
+  // test removing records
+  add_task(async function test_kinto_can_remove_some_records() {
+    let sqliteHandle = await do_get_kinto_connection();
+    let adapter = do_get_kinto_adapter(sqliteHandle);
+    // create a second record
+    let record = { id: "test-id-2", foo: "baz" };
+    await adapter.execute(transaction => transaction.create(record));
+    let newRecord = await adapter.get("test-id-2");
+    deepEqual(record, newRecord);
+    // delete the record
+    await adapter.execute(transaction => transaction.delete(record.id));
+    newRecord = await adapter.get(record.id);
+    // ... and ensure it's no longer there
+    Assert.equal(newRecord, undefined);
+    // ensure the other record still exists
+    newRecord = await adapter.get("test-id");
+    Assert.notEqual(newRecord, undefined);
+    await sqliteHandle.close();
+  });
+
+  // test getting records that don't exist
+  add_task(async function test_kinto_get_non_existant() {
+    let sqliteHandle = await do_get_kinto_connection();
+    let adapter = do_get_kinto_adapter(sqliteHandle);
+    // Kinto expects adapters to either:
+    let newRecord = await adapter.get("missing-test-id");
+    // resolve with an undefined record
+    Assert.equal(newRecord, undefined);
+    await sqliteHandle.close();
+  });
+
+  // test updating records... and getting them again
+  add_task(async function test_kinto_update_get_existing() {
+    let sqliteHandle = await do_get_kinto_connection();
+    let adapter = do_get_kinto_adapter(sqliteHandle);
+    let originalRecord = { id: "test-id", foo: "bar" };
+    let updatedRecord = { id: "test-id", foo: "baz" };
+    await adapter.clear();
+    await adapter.execute(transaction => transaction.create(originalRecord));
+    await adapter.execute(transaction => transaction.update(updatedRecord));
+    // ensure the record exists
+    let newRecord = await adapter.get("test-id");
+    // ensure the record is the same as when it was added
+    deepEqual(updatedRecord, newRecord);
+    await sqliteHandle.close();
+  });
+
+  // test listing records
+  add_task(async function test_kinto_list() {
+    let sqliteHandle = await do_get_kinto_connection();
+    let adapter = do_get_kinto_adapter(sqliteHandle);
+    let originalRecord = { id: "test-id-1", foo: "bar" };
+    let records = await adapter.list();
+    Assert.equal(records.length, 1);
+    await adapter.execute(transaction => transaction.create(originalRecord));
+    records = await adapter.list();
+    Assert.equal(records.length, 2);
+    await sqliteHandle.close();
+  });
+
+  // test aborting transaction
+  add_task(async function test_kinto_aborting_transaction() {
+    let sqliteHandle = await do_get_kinto_connection();
+    let adapter = do_get_kinto_adapter(sqliteHandle);
+    await adapter.clear();
+    let record = { id: 1, foo: "bar" };
+    let error = null;
+    try {
+      await adapter.execute(transaction => {
+        transaction.create(record);
+        throw new Error("unexpected");
+      });
+    } catch (e) {
+      error = e;
+    }
+    Assert.notEqual(error, null);
+    let records = await adapter.list();
+    Assert.equal(records.length, 0);
+    await sqliteHandle.close();
+  });
+
+  // test save and get last modified
+  add_task(async function test_kinto_last_modified() {
+    const initialValue = 0;
+    const intendedValue = 12345678;
+
+    let sqliteHandle = await do_get_kinto_connection();
+    let adapter = do_get_kinto_adapter(sqliteHandle);
+    let lastModified = await adapter.getLastModified();
+    Assert.equal(lastModified, initialValue);
+    let result = await adapter.saveLastModified(intendedValue);
+    Assert.equal(result, intendedValue);
+    lastModified = await adapter.getLastModified();
+    Assert.equal(lastModified, intendedValue);
+
+    // test saveLastModified parses values correctly
+    result = await adapter.saveLastModified(" " + intendedValue + " blah");
+    // should resolve with the parsed int
+    Assert.equal(result, intendedValue);
+    // and should have saved correctly
+    lastModified = await adapter.getLastModified();
+    Assert.equal(lastModified, intendedValue);
+    await sqliteHandle.close();
+  });
+
+  // test loadDump(records)
+  add_task(async function test_kinto_import_records() {
+    let sqliteHandle = await do_get_kinto_connection();
+    let adapter = do_get_kinto_adapter(sqliteHandle);
+    let record1 = { id: 1, foo: "bar" };
+    let record2 = { id: 2, foo: "baz" };
+    let impactedRecords = await adapter.loadDump([record1, record2]);
+    Assert.equal(impactedRecords.length, 2);
+    let newRecord1 = await adapter.get("1");
+    // ensure the record is the same as when it was added
+    deepEqual(record1, newRecord1);
+    let newRecord2 = await adapter.get("2");
+    // ensure the record is the same as when it was added
+    deepEqual(record2, newRecord2);
+    await sqliteHandle.close();
+  });
+
+  add_task(async function test_kinto_import_records_should_override_existing() {
+    let sqliteHandle = await do_get_kinto_connection();
+    let adapter = do_get_kinto_adapter(sqliteHandle);
+    await adapter.clear();
+    let records = await adapter.list();
+    Assert.equal(records.length, 0);
+    let impactedRecords = await adapter.loadDump([
+      { id: 1, foo: "bar" },
+      { id: 2, foo: "baz" },
+    ]);
+    Assert.equal(impactedRecords.length, 2);
+    await adapter.loadDump([
+      { id: 1, foo: "baz" },
+      { id: 3, foo: "bab" },
+    ]);
+    records = await adapter.list();
+    Assert.equal(records.length, 3);
+    let newRecord1 = await adapter.get("1");
+    deepEqual(newRecord1.foo, "baz");
+    await sqliteHandle.close();
+  });
+
+  add_task(async function test_import_updates_lastModified() {
+    let sqliteHandle = await do_get_kinto_connection();
+    let adapter = do_get_kinto_adapter(sqliteHandle);
+    await adapter.loadDump([
+      { id: 1, foo: "bar", last_modified: 1457896541 },
+      { id: 2, foo: "baz", last_modified: 1458796542 },
+    ]);
+    let lastModified = await adapter.getLastModified();
+    Assert.equal(lastModified, 1458796542);
+    await sqliteHandle.close();
+  });
+
+  add_task(async function test_import_preserves_older_lastModified() {
+    let sqliteHandle = await do_get_kinto_connection();
+    let adapter = do_get_kinto_adapter(sqliteHandle);
+    await adapter.saveLastModified(1458796543);
+
+    await adapter.loadDump([
+      { id: 1, foo: "bar", last_modified: 1457896541 },
+      { id: 2, foo: "baz", last_modified: 1458796542 },
+    ]);
+    let lastModified = await adapter.getLastModified();
+    Assert.equal(lastModified, 1458796543);
+    await sqliteHandle.close();
+  });
+
+  add_task(async function test_save_metadata_preserves_lastModified() {
+    let sqliteHandle = await do_get_kinto_connection();
+
+    let adapter = do_get_kinto_adapter(sqliteHandle);
+    await adapter.saveLastModified(42);
+
+    await adapter.saveMetadata({ id: "col" });
+
+    let lastModified = await adapter.getLastModified();
+    Assert.equal(lastModified, 42);
+    await sqliteHandle.close();
+  });
+}
+
+// test kinto db setup and operations in various scenarios
+// test from scratch - no current existing database
+add_test(function test_db_creation() {
+  add_test(function test_create_from_scratch() {
+    // ensure the file does not exist in the profile
+    let kintoDB = do_get_kinto_db();
+    Assert.ok(!kintoDB.exists());
+    run_next_test();
+  });
+
+  test_collection_operations();
+
+  cleanup_kinto();
+  run_next_test();
+});
+
+// this is the closest we can get to a schema version upgrade at v1 - test an
+// existing database
+add_test(function test_creation_from_empty_db() {
+  add_test(function test_create_from_empty_db() {
+    // place an empty kinto db file in the profile
+    let profile = do_get_profile();
+
+    let emptyDB = do_get_file("test_storage_adapter/empty.sqlite");
+    emptyDB.copyTo(profile, kintoFilename);
+
+    run_next_test();
+  });
+
+  test_collection_operations();
+
+  cleanup_kinto();
+  run_next_test();
+});
+
+// test schema version upgrade at v2
+add_test(function test_migration_from_v1_to_v2() {
+  add_test(function test_migrate_from_v1_to_v2() {
+    // place an empty kinto db file in the profile
+    let profile = do_get_profile();
+
+    let v1DB = do_get_file("test_storage_adapter/v1.sqlite");
+    v1DB.copyTo(profile, kintoFilename);
+
+    run_next_test();
+  });
+
+  add_test(async function schema_is_update_from_1_to_2() {
+    // The `v1.sqlite` has schema version 1.
+    let sqliteHandle = await Sqlite.openConnection({ path: kintoFilename });
+    Assert.equal(await sqliteHandle.getSchemaVersion(), 1);
+    await sqliteHandle.close();
+
+    // The `.openConnection()` migrates it to version 2.
+    sqliteHandle = await FirefoxAdapter.openConnection({ path: kintoFilename });
+    Assert.equal(await sqliteHandle.getSchemaVersion(), 2);
+    await sqliteHandle.close();
+
+    run_next_test();
+  });
+
+  test_collection_operations();
+
+  cleanup_kinto();
+  run_next_test();
+});
diff --git a/services/common/tests/unit/test_storage_adapter/empty.sqlite b/services/common/tests/unit/test_storage_adapter/empty.sqlite
new file mode 100644
index 0000000000..7f295b4146
--- /dev/null
+++ b/services/common/tests/unit/test_storage_adapter/empty.sqlite
diff --git a/services/common/tests/unit/test_storage_adapter/v1.sqlite b/services/common/tests/unit/test_storage_adapter/v1.sqlite
new file mode 100644
index 0000000000..8482b8b31d
--- /dev/null
+++ b/services/common/tests/unit/test_storage_adapter/v1.sqlite
diff --git a/services/common/tests/unit/test_storage_adapter_shutdown.js b/services/common/tests/unit/test_storage_adapter_shutdown.js
new file mode 100644
index 0000000000..dce26ce842
--- /dev/null
+++ b/services/common/tests/unit/test_storage_adapter_shutdown.js
@@ -0,0 +1,28 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { AsyncShutdown } = ChromeUtils.importESModule(
+  "resource://gre/modules/AsyncShutdown.sys.mjs"
+);
+
+const { FirefoxAdapter } = ChromeUtils.importESModule(
+  "resource://services-common/kinto-storage-adapter.sys.mjs"
+);
+
+add_task(async function test_sqlite_shutdown() {
+  const sqliteHandle = await FirefoxAdapter.openConnection({
+    path: "kinto.sqlite",
+  });
+
+  // Shutdown Sqlite.sys.mjs synchronously.
+  Services.prefs.setBoolPref("toolkit.asyncshutdown.testing", true);
+  AsyncShutdown.profileBeforeChange._trigger();
+  Services.prefs.clearUserPref("toolkit.asyncshutdown.testing");
+
+  try {
+    sqliteHandle.execute("SELECT 1;");
+    equal("Should not succeed, connection should be closed.", false);
+  } catch (e) {
+    equal(e.message, "Connection is not open.");
+  }
+});
diff --git a/services/common/tests/unit/test_tokenauthenticatedrequest.js b/services/common/tests/unit/test_tokenauthenticatedrequest.js
new file mode 100644
index 0000000000..70735894e4
--- /dev/null
+++ b/services/common/tests/unit/test_tokenauthenticatedrequest.js
@@ -0,0 +1,50 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { CryptoUtils } = ChromeUtils.importESModule(
+  "resource://services-crypto/utils.sys.mjs"
+);
+const { TokenAuthenticatedRESTRequest } = ChromeUtils.importESModule(
+  "resource://services-common/rest.sys.mjs"
+);
+
+function run_test() {
+  initTestLogging("Trace");
+  run_next_test();
+}
+
+add_task(async function test_authenticated_request() {
+  _("Ensure that sending a MAC authenticated GET request works as expected.");
+
+  let message = "Great Success!";
+
+  let id = "eyJleHBpcmVzIjogMTM2NTAxMDg5OC4x";
+  let key = "qTZf4ZFpAMpMoeSsX3zVRjiqmNs=";
+  let method = "GET";
+
+  let nonce = btoa(CryptoUtils.generateRandomBytesLegacy(16));
+  let ts = Math.floor(Date.now() / 1000);
+  let extra = { ts, nonce };
+
+  let auth;
+
+  let server = httpd_setup({
+    "/foo": function (request, response) {
+      Assert.ok(request.hasHeader("Authorization"));
+      Assert.equal(auth, request.getHeader("Authorization"));
+
+      response.setStatusLine(request.httpVersion, 200, "OK");
+      response.bodyOutputStream.write(message, message.length);
+    },
+  });
+  let uri = CommonUtils.makeURI(server.baseURI + "/foo");
+  let sig = await CryptoUtils.computeHTTPMACSHA1(id, key, method, uri, extra);
+  auth = sig.getHeader();
+
+  let req = new TokenAuthenticatedRESTRequest(uri, { id, key }, extra);
+  await req.get();
+
+  Assert.equal(message, req.response.body);
+
+  await promiseStopServer(server);
+});
diff --git a/services/common/tests/unit/test_tokenserverclient.js b/services/common/tests/unit/test_tokenserverclient.js
new file mode 100644
index 0000000000..c1c47f6e1a
--- /dev/null
+++ b/services/common/tests/unit/test_tokenserverclient.js
@@ -0,0 +1,382 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const {
+  TokenServerClient,
+  TokenServerClientError,
+  TokenServerClientServerError,
+} = ChromeUtils.importESModule(
+  "resource://services-common/tokenserverclient.sys.mjs"
+);
+
+initTestLogging("Trace");
+
+add_task(async function test_working_token_exchange() {
+  _("Ensure that working OAuth token exchange works as expected.");
+
+  let service = "http://example.com/foo";
+  let duration = 300;
+
+  let server = httpd_setup({
+    "/1.0/foo/1.0": function (request, response) {
+      Assert.ok(request.hasHeader("accept"));
+      Assert.equal("application/json", request.getHeader("accept"));
+
+      response.setStatusLine(request.httpVersion, 200, "OK");
+      response.setHeader("Content-Type", "application/json");
+
+      let body = JSON.stringify({
+        id: "id",
+        key: "key",
+        api_endpoint: service,
+        uid: "uid",
+        duration,
+      });
+      response.bodyOutputStream.write(body, body.length);
+    },
+  });
+
+  let client = new TokenServerClient();
+  let url = server.baseURI + "/1.0/foo/1.0";
+  let result = await client.getTokenUsingOAuth(url, "access_token");
+  Assert.equal("object", typeof result);
+  do_check_attribute_count(result, 7);
+  Assert.equal(service, result.endpoint);
+  Assert.equal("id", result.id);
+  Assert.equal("key", result.key);
+  Assert.equal("uid", result.uid);
+  Assert.equal(duration, result.duration);
+  Assert.deepEqual(undefined, result.node_type);
+  await promiseStopServer(server);
+});
+
+add_task(async function test_working_token_exchange_with_nodetype() {
+  _("Ensure that a token response with a node type as expected.");
+
+  let service = "http://example.com/foo";
+  let duration = 300;
+  let nodeType = "the-node-type";
+
+  let server = httpd_setup({
+    "/1.0/foo/1.0": function (request, response) {
+      Assert.ok(request.hasHeader("accept"));
+      Assert.equal("application/json", request.getHeader("accept"));
+
+      response.setStatusLine(request.httpVersion, 200, "OK");
+      response.setHeader("Content-Type", "application/json");
+
+      let body = JSON.stringify({
+        id: "id",
+        key: "key",
+        api_endpoint: service,
+        uid: "uid",
+        duration,
+        node_type: nodeType,
+      });
+      response.bodyOutputStream.write(body, body.length);
+    },
+  });
+
+  let client = new TokenServerClient();
+  let url = server.baseURI + "/1.0/foo/1.0";
+  let result = await client.getTokenUsingOAuth(url, "access_token");
+  Assert.equal("object", typeof result);
+  do_check_attribute_count(result, 7);
+  Assert.equal(service, result.endpoint);
+  Assert.equal("id", result.id);
+  Assert.equal("key", result.key);
+  Assert.equal("uid", result.uid);
+  Assert.equal(duration, result.duration);
+  Assert.equal(nodeType, result.node_type);
+  await promiseStopServer(server);
+});
+
+add_task(async function test_invalid_arguments() {
+  _("Ensure invalid arguments to APIs are rejected.");
+
+  let args = [
+    [null, "access_token"],
+    ["http://example.com/", null],
+  ];
+
+  for (let arg of args) {
+    let client = new TokenServerClient();
+    await Assert.rejects(client.getTokenUsingOAuth(arg[0], arg[1]), ex => {
+      Assert.ok(ex instanceof TokenServerClientError);
+      return true;
+    });
+  }
+});
+
+add_task(async function test_invalid_403_no_content_type() {
+  _("Ensure that a 403 without content-type is handled properly.");
+
+  let server = httpd_setup({
+    "/1.0/foo/1.0": function (request, response) {
+      response.setStatusLine(request.httpVersion, 403, "Forbidden");
+      // No Content-Type header by design.
+
+      let body = JSON.stringify({
+        errors: [{ description: "irrelevant", location: "body", name: "" }],
+        urls: { foo: "http://bar" },
+      });
+      response.bodyOutputStream.write(body, body.length);
+    },
+  });
+
+  let client = new TokenServerClient();
+  let url = server.baseURI + "/1.0/foo/1.0";
+
+  await Assert.rejects(
+    client.getTokenUsingOAuth(url, "access_token"),
+    error => {
+      Assert.ok(error instanceof TokenServerClientServerError);
+      Assert.equal(error.cause, "malformed-response");
+
+      Assert.equal(null, error.urls);
+      return true;
+    }
+  );
+
+  await promiseStopServer(server);
+});
+
+add_task(async function test_send_extra_headers() {
+  _("Ensures that the condition acceptance header is sent when asked.");
+
+  let duration = 300;
+  let server = httpd_setup({
+    "/1.0/foo/1.0": function (request, response) {
+      Assert.ok(request.hasHeader("x-foo"));
+      Assert.equal(request.getHeader("x-foo"), "42");
+
+      Assert.ok(request.hasHeader("x-bar"));
+      Assert.equal(request.getHeader("x-bar"), "17");
+
+      response.setStatusLine(request.httpVersion, 200, "OK");
+      response.setHeader("Content-Type", "application/json");
+
+      let body = JSON.stringify({
+        id: "id",
+        key: "key",
+        api_endpoint: "http://example.com/",
+        uid: "uid",
+        duration,
+      });
+      response.bodyOutputStream.write(body, body.length);
+    },
+  });
+
+  let client = new TokenServerClient();
+  let url = server.baseURI + "/1.0/foo/1.0";
+
+  let extra = {
+    "X-Foo": 42,
+    "X-Bar": 17,
+  };
+
+  await client.getTokenUsingOAuth(url, "access_token", extra);
+  // Other tests validate other things.
+
+  await promiseStopServer(server);
+});
+
+add_task(async function test_error_404_empty() {
+  _("Ensure that 404 responses without proper response are handled properly.");
+
+  let server = httpd_setup();
+
+  let client = new TokenServerClient();
+  let url = server.baseURI + "/foo";
+
+  await Assert.rejects(
+    client.getTokenUsingOAuth(url, "access_token"),
+    error => {
+      Assert.ok(error instanceof TokenServerClientServerError);
+      Assert.equal(error.cause, "malformed-response");
+
+      Assert.notEqual(null, error.response);
+      return true;
+    }
+  );
+
+  await promiseStopServer(server);
+});
+
+add_task(async function test_error_404_proper_response() {
+  _("Ensure that a Cornice error report for 404 is handled properly.");
+
+  let server = httpd_setup({
+    "/1.0/foo/1.0": function (request, response) {
+      response.setStatusLine(request.httpVersion, 404, "Not Found");
+      response.setHeader("Content-Type", "application/json; charset=utf-8");
+
+      let body = JSON.stringify({
+        status: 404,
+        errors: [{ description: "No service", location: "body", name: "" }],
+      });
+
+      response.bodyOutputStream.write(body, body.length);
+    },
+  });
+
+  let client = new TokenServerClient();
+  let url = server.baseURI + "/1.0/foo/1.0";
+
+  await Assert.rejects(
+    client.getTokenUsingOAuth(url, "access_token"),
+    error => {
+      Assert.ok(error instanceof TokenServerClientServerError);
+      Assert.equal(error.cause, "unknown-service");
+      return true;
+    }
+  );
+
+  await promiseStopServer(server);
+});
+
+add_task(async function test_bad_json() {
+  _("Ensure that malformed JSON is handled properly.");
+
+  let server = httpd_setup({
+    "/1.0/foo/1.0": function (request, response) {
+      response.setStatusLine(request.httpVersion, 200, "OK");
+      response.setHeader("Content-Type", "application/json");
+
+      let body = '{"id": "id", baz}';
+      response.bodyOutputStream.write(body, body.length);
+    },
+  });
+
+  let client = new TokenServerClient();
+  let url = server.baseURI + "/1.0/foo/1.0";
+
+  await Assert.rejects(
+    client.getTokenUsingOAuth(url, "access_token"),
+    error => {
+      Assert.notEqual(null, error);
+      Assert.equal("TokenServerClientServerError", error.name);
+      Assert.equal(error.cause, "malformed-response");
+      Assert.notEqual(null, error.response);
+      return true;
+    }
+  );
+
+  await promiseStopServer(server);
+});
+
+add_task(async function test_400_response() {
+  _("Ensure HTTP 400 is converted to malformed-request.");
+
+  let server = httpd_setup({
+    "/1.0/foo/1.0": function (request, response) {
+      response.setStatusLine(request.httpVersion, 400, "Bad Request");
+      response.setHeader("Content-Type", "application/json; charset=utf-8");
+
+      let body = "{}"; // Actual content may not be used.
+      response.bodyOutputStream.write(body, body.length);
+    },
+  });
+
+  let client = new TokenServerClient();
+  let url = server.baseURI + "/1.0/foo/1.0";
+
+  await Assert.rejects(
+    client.getTokenUsingOAuth(url, "access_token"),
+    error => {
+      Assert.notEqual(null, error);
+      Assert.equal("TokenServerClientServerError", error.name);
+      Assert.notEqual(null, error.response);
+      Assert.equal(error.cause, "malformed-request");
+      return true;
+    }
+  );
+
+  await promiseStopServer(server);
+});
+
+add_task(async function test_401_with_error_cause() {
+  _("Ensure 401 cause is specified in body.status");
+
+  let server = httpd_setup({
+    "/1.0/foo/1.0": function (request, response) {
+      response.setStatusLine(request.httpVersion, 401, "Unauthorized");
+      response.setHeader("Content-Type", "application/json; charset=utf-8");
+
+      let body = JSON.stringify({ status: "no-soup-for-you" });
+      response.bodyOutputStream.write(body, body.length);
+    },
+  });
+
+  let client = new TokenServerClient();
+  let url = server.baseURI + "/1.0/foo/1.0";
+
+  await Assert.rejects(
+    client.getTokenUsingOAuth(url, "access_token"),
+    error => {
+      Assert.notEqual(null, error);
+      Assert.equal("TokenServerClientServerError", error.name);
+      Assert.notEqual(null, error.response);
+      Assert.equal(error.cause, "no-soup-for-you");
+      return true;
+    }
+  );
+
+  await promiseStopServer(server);
+});
+
+add_task(async function test_unhandled_media_type() {
+  _("Ensure that unhandled media types throw an error.");
+
+  let server = httpd_setup({
+    "/1.0/foo/1.0": function (request, response) {
+      response.setStatusLine(request.httpVersion, 200, "OK");
+      response.setHeader("Content-Type", "text/plain");
+
+      let body = "hello, world";
+      response.bodyOutputStream.write(body, body.length);
+    },
+  });
+
+  let url = server.baseURI + "/1.0/foo/1.0";
+  let client = new TokenServerClient();
+
+  await Assert.rejects(
+    client.getTokenUsingOAuth(url, "access_token"),
+    error => {
+      Assert.notEqual(null, error);
+      Assert.equal("TokenServerClientServerError", error.name);
+      Assert.notEqual(null, error.response);
+      return true;
+    }
+  );
+
+  await promiseStopServer(server);
+});
+
+add_task(async function test_rich_media_types() {
+  _("Ensure that extra tokens in the media type aren't rejected.");
+
+  let duration = 300;
+  let server = httpd_setup({
+    "/foo": function (request, response) {
+      response.setStatusLine(request.httpVersion, 200, "OK");
+      response.setHeader("Content-Type", "application/json; foo=bar; bar=foo");
+
+      let body = JSON.stringify({
+        id: "id",
+        key: "key",
+        api_endpoint: "foo",
+        uid: "uid",
+        duration,
+      });
+      response.bodyOutputStream.write(body, body.length);
+    },
+  });
+
+  let url = server.baseURI + "/foo";
+  let client = new TokenServerClient();
+
+  await client.getTokenUsingOAuth(url, "access_token");
+  await promiseStopServer(server);
+});
diff --git a/services/common/tests/unit/test_uptake_telemetry.js b/services/common/tests/unit/test_uptake_telemetry.js
new file mode 100644
index 0000000000..24967b641f
--- /dev/null
+++ b/services/common/tests/unit/test_uptake_telemetry.js
@@ -0,0 +1,121 @@
+const { TelemetryTestUtils } = ChromeUtils.importESModule(
+  "resource://testing-common/TelemetryTestUtils.sys.mjs"
+);
+const { UptakeTelemetry } = ChromeUtils.importESModule(
+  "resource://services-common/uptake-telemetry.sys.mjs"
+);
+
+const COMPONENT = "remotesettings";
+
+async function withFakeClientID(uuid, f) {
+  const { Policy } = ChromeUtils.importESModule(
+    "resource://services-common/uptake-telemetry.sys.mjs"
+  );
+  let oldGetClientID = Policy.getClientID;
+  Policy._clientIDHash = null;
+  Policy.getClientID = () => Promise.resolve(uuid);
+  try {
+    return await f();
+  } finally {
+    Policy.getClientID = oldGetClientID;
+  }
+}
+
+add_task(async function test_unknown_status_is_not_reported() {
+  const source = "update-source";
+  const startSnapshot = getUptakeTelemetrySnapshot(COMPONENT, source);
+
+  try {
+    await UptakeTelemetry.report(COMPONENT, "unknown-status", { source });
+  } catch (e) {}
+
+  const endSnapshot = getUptakeTelemetrySnapshot(COMPONENT, source);
+  Assert.deepEqual(startSnapshot, endSnapshot);
+});
+
+add_task(async function test_age_is_converted_to_string_and_reported() {
+  const status = UptakeTelemetry.STATUS.SUCCESS;
+  const age = 42;
+
+  await withFakeChannel("nightly", async () => {
+    await UptakeTelemetry.report(COMPONENT, status, { source: "s", age });
+  });
+
+  TelemetryTestUtils.assertEvents([
+    [
+      "uptake.remotecontent.result",
+      "uptake",
+      COMPONENT,
+      status,
+      { source: "s", age: `${age}` },
+    ],
+  ]);
+});
+
+add_task(async function test_each_status_can_be_caught_in_snapshot() {
+  const source = "some-source";
+  const startSnapshot = getUptakeTelemetrySnapshot(COMPONENT, source);
+
+  const expectedIncrements = {};
+  await withFakeChannel("nightly", async () => {
+    for (const status of Object.values(UptakeTelemetry.STATUS)) {
+      expectedIncrements[status] = 1;
+      await UptakeTelemetry.report(COMPONENT, status, { source });
+    }
+  });
+
+  const endSnapshot = getUptakeTelemetrySnapshot(COMPONENT, source);
+  checkUptakeTelemetry(startSnapshot, endSnapshot, expectedIncrements);
+});
+
+add_task(async function test_events_are_sent_when_hash_is_mod_0() {
+  const source = "some-source";
+  const startSnapshot = getUptakeTelemetrySnapshot(COMPONENT, source);
+  const startSuccess = startSnapshot.success || 0;
+  const uuid = "d81bbfad-d741-41f5-a7e6-29f6bde4972a"; // hash % 100 = 0
+  await withFakeClientID(uuid, async () => {
+    await withFakeChannel("release", async () => {
+      await UptakeTelemetry.report(COMPONENT, UptakeTelemetry.STATUS.SUCCESS, {
+        source,
+      });
+    });
+  });
+  const endSnapshot = getUptakeTelemetrySnapshot(COMPONENT, source);
+  Assert.equal(endSnapshot.success, startSuccess + 1);
+});
+
+add_task(
+  async function test_events_are_not_sent_when_hash_is_greater_than_pref() {
+    const source = "some-source";
+    const startSnapshot = getUptakeTelemetrySnapshot(COMPONENT, source);
+    const startSuccess = startSnapshot.success || 0;
+    const uuid = "d81bbfad-d741-41f5-a7e6-29f6bde49721"; // hash % 100 = 1
+    await withFakeClientID(uuid, async () => {
+      await withFakeChannel("release", async () => {
+        await UptakeTelemetry.report(
+          COMPONENT,
+          UptakeTelemetry.STATUS.SUCCESS,
+          { source }
+        );
+      });
+    });
+    const endSnapshot = getUptakeTelemetrySnapshot(COMPONENT, source);
+    Assert.equal(endSnapshot.success || 0, startSuccess);
+  }
+);
+
+add_task(async function test_events_are_sent_when_nightly() {
+  const source = "some-source";
+  const startSnapshot = getUptakeTelemetrySnapshot(COMPONENT, source);
+  const startSuccess = startSnapshot.success || 0;
+  const uuid = "d81bbfad-d741-41f5-a7e6-29f6bde49721"; // hash % 100 = 1
+  await withFakeClientID(uuid, async () => {
+    await withFakeChannel("nightly", async () => {
+      await UptakeTelemetry.report(COMPONENT, UptakeTelemetry.STATUS.SUCCESS, {
+        source,
+      });
+    });
+  });
+  const endSnapshot = getUptakeTelemetrySnapshot(COMPONENT, source);
+  Assert.equal(endSnapshot.success, startSuccess + 1);
+});
diff --git a/services/common/tests/unit/test_utils_atob.js b/services/common/tests/unit/test_utils_atob.js
new file mode 100644
index 0000000000..9e24b56f6f
--- /dev/null
+++ b/services/common/tests/unit/test_utils_atob.js
@@ -0,0 +1,9 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+function run_test() {
+  let data = ["Zm9vYmE=", "Zm9vYmE==", "Zm9vYmE==="];
+  for (let d in data) {
+    Assert.equal(CommonUtils.safeAtoB(data[d]), "fooba");
+  }
+}
diff --git a/services/common/tests/unit/test_utils_convert_string.js b/services/common/tests/unit/test_utils_convert_string.js
new file mode 100644
index 0000000000..fcfd874994
--- /dev/null
+++ b/services/common/tests/unit/test_utils_convert_string.js
@@ -0,0 +1,146 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+// A wise line of Greek verse, and the utf-8 byte encoding.
+// N.b., Greek begins at utf-8 ce 91
+const TEST_STR = "πόλλ' οἶδ' ἀλώπηξ, ἀλλ' ἐχῖνος ἓν μέγα";
+const TEST_HEX = h(
+  "cf 80 cf 8c ce bb ce bb   27 20 ce bf e1 bc b6 ce" +
+    "b4 27 20 e1 bc 80 ce bb   cf 8e cf 80 ce b7 ce be" +
+    "2c 20 e1 bc 80 ce bb ce   bb 27 20 e1 bc 90 cf 87" +
+    "e1 bf 96 ce bd ce bf cf   82 20 e1 bc 93 ce bd 20" +
+    "ce bc ce ad ce b3 ce b1"
+);
+// Integer byte values for the above
+const TEST_BYTES = [
+  207, 128, 207, 140, 206, 187, 206, 187, 39, 32, 206, 191, 225, 188, 182, 206,
+  180, 39, 32, 225, 188, 128, 206, 187, 207, 142, 207, 128, 206, 183, 206, 190,
+  44, 32, 225, 188, 128, 206, 187, 206, 187, 39, 32, 225, 188, 144, 207, 135,
+  225, 191, 150, 206, 189, 206, 191, 207, 130, 32, 225, 188, 147, 206, 189, 32,
+  206, 188, 206, 173, 206, 179, 206, 177,
+];
+
+add_test(function test_compress_string() {
+  const INPUT = "hello";
+
+  let result = CommonUtils.convertString(INPUT, "uncompressed", "deflate");
+  Assert.equal(result.length, 13);
+
+  let result2 = CommonUtils.convertString(INPUT, "uncompressed", "deflate");
+  Assert.equal(result, result2);
+
+  let result3 = CommonUtils.convertString(result, "deflate", "uncompressed");
+  Assert.equal(result3, INPUT);
+
+  run_next_test();
+});
+
+add_test(function test_compress_utf8() {
+  const INPUT =
+    "Árvíztűrő tükörfúrógép いろはにほへとちりぬるを Pijamalı hasta, yağız şoföre çabucak güvendi.";
+  let inputUTF8 = CommonUtils.encodeUTF8(INPUT);
+
+  let compressed = CommonUtils.convertString(
+    inputUTF8,
+    "uncompressed",
+    "deflate"
+  );
+  let uncompressed = CommonUtils.convertString(
+    compressed,
+    "deflate",
+    "uncompressed"
+  );
+
+  Assert.equal(uncompressed, inputUTF8);
+
+  let outputUTF8 = CommonUtils.decodeUTF8(uncompressed);
+  Assert.equal(outputUTF8, INPUT);
+
+  run_next_test();
+});
+
+add_test(function test_bad_argument() {
+  let failed = false;
+  try {
+    CommonUtils.convertString(null, "uncompressed", "deflate");
+  } catch (ex) {
+    failed = true;
+    Assert.ok(ex.message.startsWith("Input string must be defined"));
+  } finally {
+    Assert.ok(failed);
+  }
+
+  run_next_test();
+});
+
+add_task(function test_stringAsHex() {
+  Assert.equal(TEST_HEX, CommonUtils.stringAsHex(TEST_STR));
+});
+
+add_task(function test_hexAsString() {
+  Assert.equal(TEST_STR, CommonUtils.hexAsString(TEST_HEX));
+});
+
+add_task(function test_hexToBytes() {
+  let bytes = CommonUtils.hexToBytes(TEST_HEX);
+  Assert.equal(TEST_BYTES.length, bytes.length);
+  // Ensure that the decimal values of each byte are correct
+  Assert.ok(arraysEqual(TEST_BYTES, CommonUtils.stringToByteArray(bytes)));
+});
+
+add_task(function test_bytesToHex() {
+  // Create a list of our character bytes from the reference int values
+  let bytes = CommonUtils.byteArrayToString(TEST_BYTES);
+  Assert.equal(TEST_HEX, CommonUtils.bytesAsHex(bytes));
+});
+
+add_task(function test_stringToBytes() {
+  Assert.ok(
+    arraysEqual(
+      TEST_BYTES,
+      CommonUtils.stringToByteArray(CommonUtils.stringToBytes(TEST_STR))
+    )
+  );
+});
+
+add_task(function test_stringRoundTrip() {
+  Assert.equal(
+    TEST_STR,
+    CommonUtils.hexAsString(CommonUtils.stringAsHex(TEST_STR))
+  );
+});
+
+add_task(function test_hexRoundTrip() {
+  Assert.equal(
+    TEST_HEX,
+    CommonUtils.stringAsHex(CommonUtils.hexAsString(TEST_HEX))
+  );
+});
+
+add_task(function test_byteArrayRoundTrip() {
+  Assert.ok(
+    arraysEqual(
+      TEST_BYTES,
+      CommonUtils.stringToByteArray(CommonUtils.byteArrayToString(TEST_BYTES))
+    )
+  );
+});
+
+// turn formatted test vectors into normal hex strings
+function h(hexStr) {
+  return hexStr.replace(/\s+/g, "");
+}
+
+function arraysEqual(a1, a2) {
+  if (a1.length !== a2.length) {
+    return false;
+  }
+  for (let i = 0; i < a1.length; i++) {
+    if (a1[i] !== a2[i]) {
+      return false;
+    }
+  }
+  return true;
+}
diff --git a/services/common/tests/unit/test_utils_dateprefs.js b/services/common/tests/unit/test_utils_dateprefs.js
new file mode 100644
index 0000000000..0a79ac436a
--- /dev/null
+++ b/services/common/tests/unit/test_utils_dateprefs.js
@@ -0,0 +1,81 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const { Preferences } = ChromeUtils.importESModule(
+  "resource://gre/modules/Preferences.sys.mjs"
+);
+
+var prefs = new Preferences("servicescommon.tests.");
+
+function DummyLogger() {
+  this.messages = [];
+}
+DummyLogger.prototype.warn = function warn(message) {
+  this.messages.push(message);
+};
+
+add_test(function test_set_basic() {
+  let now = new Date();
+
+  CommonUtils.setDatePref(prefs, "test00", now);
+  let value = prefs.get("test00");
+  Assert.equal(value, "" + now.getTime());
+
+  let now2 = CommonUtils.getDatePref(prefs, "test00");
+
+  Assert.equal(now.getTime(), now2.getTime());
+
+  run_next_test();
+});
+
+add_test(function test_set_bounds_checking() {
+  let d = new Date(2342354);
+
+  let failed = false;
+  try {
+    CommonUtils.setDatePref(prefs, "test01", d);
+  } catch (ex) {
+    Assert.ok(ex.message.startsWith("Trying to set"));
+    failed = true;
+  }
+
+  Assert.ok(failed);
+  run_next_test();
+});
+
+add_test(function test_get_bounds_checking() {
+  prefs.set("test_bounds_checking", "13241431");
+
+  let log = new DummyLogger();
+  let d = CommonUtils.getDatePref(prefs, "test_bounds_checking", 0, log);
+  Assert.equal(d.getTime(), 0);
+  Assert.equal(log.messages.length, 1);
+
+  run_next_test();
+});
+
+add_test(function test_get_bad_default() {
+  let failed = false;
+  try {
+    CommonUtils.getDatePref(prefs, "get_bad_default", new Date());
+  } catch (ex) {
+    Assert.ok(ex.message.startsWith("Default value is not a number"));
+    failed = true;
+  }
+
+  Assert.ok(failed);
+  run_next_test();
+});
+
+add_test(function test_get_invalid_number() {
+  prefs.set("get_invalid_number", "hello world");
+
+  let log = new DummyLogger();
+  let d = CommonUtils.getDatePref(prefs, "get_invalid_number", 42, log);
+  Assert.equal(d.getTime(), 42);
+  Assert.equal(log.messages.length, 1);
+
+  run_next_test();
+});
diff --git a/services/common/tests/unit/test_utils_encodeBase32.js b/services/common/tests/unit/test_utils_encodeBase32.js
new file mode 100644
index 0000000000..3299ac8d05
--- /dev/null
+++ b/services/common/tests/unit/test_utils_encodeBase32.js
@@ -0,0 +1,55 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+function run_test() {
+  // Testing byte array manipulation.
+  Assert.equal(
+    "FOOBAR",
+    CommonUtils.byteArrayToString([70, 79, 79, 66, 65, 82])
+  );
+  Assert.equal("", CommonUtils.byteArrayToString([]));
+
+  _("Testing encoding...");
+  // Test vectors from RFC 4648
+  Assert.equal(CommonUtils.encodeBase32(""), "");
+  Assert.equal(CommonUtils.encodeBase32("f"), "MY======");
+  Assert.equal(CommonUtils.encodeBase32("fo"), "MZXQ====");
+  Assert.equal(CommonUtils.encodeBase32("foo"), "MZXW6===");
+  Assert.equal(CommonUtils.encodeBase32("foob"), "MZXW6YQ=");
+  Assert.equal(CommonUtils.encodeBase32("fooba"), "MZXW6YTB");
+  Assert.equal(CommonUtils.encodeBase32("foobar"), "MZXW6YTBOI======");
+
+  Assert.equal(
+    CommonUtils.encodeBase32("Bacon is a vegetable."),
+    "IJQWG33OEBUXGIDBEB3GKZ3FORQWE3DFFY======"
+  );
+
+  _("Checking assumptions...");
+  for (let i = 0; i <= 255; ++i) {
+    Assert.equal(undefined | i, i);
+  }
+
+  _("Testing decoding...");
+  Assert.equal(CommonUtils.decodeBase32(""), "");
+  Assert.equal(CommonUtils.decodeBase32("MY======"), "f");
+  Assert.equal(CommonUtils.decodeBase32("MZXQ===="), "fo");
+  Assert.equal(CommonUtils.decodeBase32("MZXW6YTB"), "fooba");
+  Assert.equal(CommonUtils.decodeBase32("MZXW6YTBOI======"), "foobar");
+
+  // Same with incorrect or missing padding.
+  Assert.equal(CommonUtils.decodeBase32("MZXW6YTBOI=="), "foobar");
+  Assert.equal(CommonUtils.decodeBase32("MZXW6YTBOI"), "foobar");
+
+  let encoded = CommonUtils.encodeBase32("Bacon is a vegetable.");
+  _("Encoded to " + JSON.stringify(encoded));
+  Assert.equal(CommonUtils.decodeBase32(encoded), "Bacon is a vegetable.");
+
+  // Test failure.
+  let err;
+  try {
+    CommonUtils.decodeBase32("000");
+  } catch (ex) {
+    err = ex;
+  }
+  Assert.equal(err.message, "Unknown character in base32: 0");
+}
diff --git a/services/common/tests/unit/test_utils_encodeBase64URL.js b/services/common/tests/unit/test_utils_encodeBase64URL.js
new file mode 100644
index 0000000000..84d98b06f1
--- /dev/null
+++ b/services/common/tests/unit/test_utils_encodeBase64URL.js
@@ -0,0 +1,21 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+add_test(function test_simple() {
+  let expected = {
+    hello: "aGVsbG8=",
+    "<>?": "PD4_",
+  };
+
+  for (let [k, v] of Object.entries(expected)) {
+    Assert.equal(CommonUtils.encodeBase64URL(k), v);
+  }
+
+  run_next_test();
+});
+
+add_test(function test_no_padding() {
+  Assert.equal(CommonUtils.encodeBase64URL("hello", false), "aGVsbG8");
+
+  run_next_test();
+});
diff --git a/services/common/tests/unit/test_utils_ensureMillisecondsTimestamp.js b/services/common/tests/unit/test_utils_ensureMillisecondsTimestamp.js
new file mode 100644
index 0000000000..f334364b2d
--- /dev/null
+++ b/services/common/tests/unit/test_utils_ensureMillisecondsTimestamp.js
@@ -0,0 +1,40 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+function run_test() {
+  Assert.equal(null, CommonUtils.ensureMillisecondsTimestamp(null));
+  Assert.equal(null, CommonUtils.ensureMillisecondsTimestamp(0));
+  Assert.equal(null, CommonUtils.ensureMillisecondsTimestamp("0"));
+  Assert.equal(null, CommonUtils.ensureMillisecondsTimestamp("000"));
+
+  Assert.equal(
+    null,
+    CommonUtils.ensureMillisecondsTimestamp(999 * 10000000000)
+  );
+
+  do_check_throws(function err() {
+    CommonUtils.ensureMillisecondsTimestamp(-1);
+  });
+  do_check_throws(function err() {
+    CommonUtils.ensureMillisecondsTimestamp(1);
+  });
+  do_check_throws(function err() {
+    CommonUtils.ensureMillisecondsTimestamp(1.5);
+  });
+  do_check_throws(function err() {
+    CommonUtils.ensureMillisecondsTimestamp(999 * 10000000000 + 0.5);
+  });
+
+  do_check_throws(function err() {
+    CommonUtils.ensureMillisecondsTimestamp("-1");
+  });
+  do_check_throws(function err() {
+    CommonUtils.ensureMillisecondsTimestamp("1");
+  });
+  do_check_throws(function err() {
+    CommonUtils.ensureMillisecondsTimestamp("1.5");
+  });
+  do_check_throws(function err() {
+    CommonUtils.ensureMillisecondsTimestamp("" + (999 * 10000000000 + 0.5));
+  });
+}
diff --git a/services/common/tests/unit/test_utils_makeURI.js b/services/common/tests/unit/test_utils_makeURI.js
new file mode 100644
index 0000000000..d6d7e19db9
--- /dev/null
+++ b/services/common/tests/unit/test_utils_makeURI.js
@@ -0,0 +1,62 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+_("Make sure uri strings are converted to nsIURIs");
+
+function run_test() {
+  _test_makeURI();
+}
+
+function _test_makeURI() {
+  _("Check http uris");
+  let uri1 = "http://mozillalabs.com/";
+  Assert.equal(CommonUtils.makeURI(uri1).spec, uri1);
+  let uri2 = "http://www.mozillalabs.com/";
+  Assert.equal(CommonUtils.makeURI(uri2).spec, uri2);
+  let uri3 = "http://mozillalabs.com/path";
+  Assert.equal(CommonUtils.makeURI(uri3).spec, uri3);
+  let uri4 = "http://mozillalabs.com/multi/path";
+  Assert.equal(CommonUtils.makeURI(uri4).spec, uri4);
+  let uri5 = "http://mozillalabs.com/?query";
+  Assert.equal(CommonUtils.makeURI(uri5).spec, uri5);
+  let uri6 = "http://mozillalabs.com/#hash";
+  Assert.equal(CommonUtils.makeURI(uri6).spec, uri6);
+
+  _("Check https uris");
+  let uris1 = "https://mozillalabs.com/";
+  Assert.equal(CommonUtils.makeURI(uris1).spec, uris1);
+  let uris2 = "https://www.mozillalabs.com/";
+  Assert.equal(CommonUtils.makeURI(uris2).spec, uris2);
+  let uris3 = "https://mozillalabs.com/path";
+  Assert.equal(CommonUtils.makeURI(uris3).spec, uris3);
+  let uris4 = "https://mozillalabs.com/multi/path";
+  Assert.equal(CommonUtils.makeURI(uris4).spec, uris4);
+  let uris5 = "https://mozillalabs.com/?query";
+  Assert.equal(CommonUtils.makeURI(uris5).spec, uris5);
+  let uris6 = "https://mozillalabs.com/#hash";
+  Assert.equal(CommonUtils.makeURI(uris6).spec, uris6);
+
+  _("Check chrome uris");
+  let uric1 = "chrome://browser/content/browser.xhtml";
+  Assert.equal(CommonUtils.makeURI(uric1).spec, uric1);
+  let uric2 = "chrome://browser/skin/browser.css";
+  Assert.equal(CommonUtils.makeURI(uric2).spec, uric2);
+
+  _("Check about uris");
+  let uria1 = "about:weave";
+  Assert.equal(CommonUtils.makeURI(uria1).spec, uria1);
+  let uria2 = "about:weave/";
+  Assert.equal(CommonUtils.makeURI(uria2).spec, uria2);
+  let uria3 = "about:weave/path";
+  Assert.equal(CommonUtils.makeURI(uria3).spec, uria3);
+  let uria4 = "about:weave/multi/path";
+  Assert.equal(CommonUtils.makeURI(uria4).spec, uria4);
+  let uria5 = "about:weave/?query";
+  Assert.equal(CommonUtils.makeURI(uria5).spec, uria5);
+  let uria6 = "about:weave/#hash";
+  Assert.equal(CommonUtils.makeURI(uria6).spec, uria6);
+
+  _("Invalid uris are undefined");
+  Assert.equal(CommonUtils.makeURI("mozillalabs.com"), undefined);
+  Assert.equal(CommonUtils.makeURI("this is a test"), undefined);
+}
diff --git a/services/common/tests/unit/test_utils_namedTimer.js b/services/common/tests/unit/test_utils_namedTimer.js
new file mode 100644
index 0000000000..47ac0b9dc1
--- /dev/null
+++ b/services/common/tests/unit/test_utils_namedTimer.js
@@ -0,0 +1,73 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+add_test(function test_required_args() {
+  try {
+    CommonUtils.namedTimer(function callback() {
+      do_throw("Shouldn't fire.");
+    }, 0);
+    do_throw("Should have thrown!");
+  } catch (ex) {
+    run_next_test();
+  }
+});
+
+add_test(function test_simple() {
+  _("Test basic properties of CommonUtils.namedTimer.");
+
+  const delay = 200;
+  let that = {};
+  let t0 = Date.now();
+  CommonUtils.namedTimer(
+    function callback(timer) {
+      Assert.equal(this, that);
+      Assert.equal(this._zetimer, null);
+      Assert.ok(timer instanceof Ci.nsITimer);
+      // Difference should be ~delay, but hard to predict on all platforms,
+      // particularly Windows XP.
+      Assert.ok(Date.now() > t0);
+      run_next_test();
+    },
+    delay,
+    that,
+    "_zetimer"
+  );
+});
+
+add_test(function test_delay() {
+  _("Test delaying a timer that hasn't fired yet.");
+
+  const delay = 100;
+  let that = {};
+  let t0 = Date.now();
+  function callback(timer) {
+    // Difference should be ~2*delay, but hard to predict on all platforms,
+    // particularly Windows XP.
+    Assert.ok(Date.now() - t0 > delay);
+    run_next_test();
+  }
+  CommonUtils.namedTimer(callback, delay, that, "_zetimer");
+  CommonUtils.namedTimer(callback, 2 * delay, that, "_zetimer");
+  run_next_test();
+});
+
+add_test(function test_clear() {
+  _("Test clearing a timer that hasn't fired yet.");
+
+  const delay = 0;
+  let that = {};
+  CommonUtils.namedTimer(
+    function callback(timer) {
+      do_throw("Shouldn't fire!");
+    },
+    delay,
+    that,
+    "_zetimer"
+  );
+
+  that._zetimer.clear();
+  Assert.equal(that._zetimer, null);
+  CommonUtils.nextTick(run_next_test);
+
+  run_next_test();
+});
diff --git a/services/common/tests/unit/test_utils_sets.js b/services/common/tests/unit/test_utils_sets.js
new file mode 100644
index 0000000000..c15d48528f
--- /dev/null
+++ b/services/common/tests/unit/test_utils_sets.js
@@ -0,0 +1,66 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const EMPTY = new Set();
+const A = new Set(["a"]);
+const ABC = new Set(["a", "b", "c"]);
+const ABCD = new Set(["a", "b", "c", "d"]);
+const BC = new Set(["b", "c"]);
+const BCD = new Set(["b", "c", "d"]);
+const FGH = new Set(["f", "g", "h"]);
+const BCDFGH = new Set(["b", "c", "d", "f", "g", "h"]);
+
+var union = CommonUtils.union;
+var difference = CommonUtils.difference;
+var intersection = CommonUtils.intersection;
+var setEqual = CommonUtils.setEqual;
+
+function do_check_setEqual(a, b) {
+  Assert.ok(setEqual(a, b));
+}
+
+function do_check_not_setEqual(a, b) {
+  Assert.ok(!setEqual(a, b));
+}
+
+add_test(function test_setEqual() {
+  do_check_setEqual(EMPTY, EMPTY);
+  do_check_setEqual(EMPTY, new Set());
+  do_check_setEqual(A, A);
+  do_check_setEqual(A, new Set(["a"]));
+  do_check_setEqual(new Set(["a"]), A);
+  do_check_not_setEqual(A, EMPTY);
+  do_check_not_setEqual(EMPTY, A);
+  do_check_not_setEqual(ABC, A);
+  run_next_test();
+});
+
+add_test(function test_union() {
+  do_check_setEqual(EMPTY, union(EMPTY, EMPTY));
+  do_check_setEqual(ABC, union(EMPTY, ABC));
+  do_check_setEqual(ABC, union(ABC, ABC));
+  do_check_setEqual(ABCD, union(ABC, BCD));
+  do_check_setEqual(ABCD, union(BCD, ABC));
+  do_check_setEqual(BCDFGH, union(BCD, FGH));
+  run_next_test();
+});
+
+add_test(function test_difference() {
+  do_check_setEqual(EMPTY, difference(EMPTY, EMPTY));
+  do_check_setEqual(EMPTY, difference(EMPTY, A));
+  do_check_setEqual(EMPTY, difference(A, A));
+  do_check_setEqual(ABC, difference(ABC, EMPTY));
+  do_check_setEqual(ABC, difference(ABC, FGH));
+  do_check_setEqual(A, difference(ABC, BCD));
+  run_next_test();
+});
+
+add_test(function test_intersection() {
+  do_check_setEqual(EMPTY, intersection(EMPTY, EMPTY));
+  do_check_setEqual(EMPTY, intersection(ABC, EMPTY));
+  do_check_setEqual(EMPTY, intersection(ABC, FGH));
+  do_check_setEqual(BC, intersection(ABC, BCD));
+  run_next_test();
+});
diff --git a/services/common/tests/unit/test_utils_utf8.js b/services/common/tests/unit/test_utils_utf8.js
new file mode 100644
index 0000000000..aa075873b9
--- /dev/null
+++ b/services/common/tests/unit/test_utils_utf8.js
@@ -0,0 +1,9 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+function run_test() {
+  let str = "Umlaute: \u00FC \u00E4\n"; // Umlaute: ü ä
+  let encoded = CommonUtils.encodeUTF8(str);
+  let decoded = CommonUtils.decodeUTF8(encoded);
+  Assert.equal(decoded, str);
+}
diff --git a/services/common/tests/unit/test_utils_uuid.js b/services/common/tests/unit/test_utils_uuid.js
new file mode 100644
index 0000000000..33b407e92d
--- /dev/null
+++ b/services/common/tests/unit/test_utils_uuid.js
@@ -0,0 +1,12 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+function run_test() {
+  let uuid = CommonUtils.generateUUID();
+  Assert.equal(uuid.length, 36);
+  Assert.equal(uuid[8], "-");
+
+  run_next_test();
+}
diff --git a/services/common/tests/unit/xpcshell.ini b/services/common/tests/unit/xpcshell.ini
new file mode 100644
index 0000000000..5fdf8d423b
--- /dev/null
+++ b/services/common/tests/unit/xpcshell.ini
@@ -0,0 +1,47 @@
+[DEFAULT]
+head = head_global.js head_helpers.js head_http.js
+firefox-appdir = browser
+support-files =
+  test_storage_adapter/**
+
+# Test load modules first so syntax failures are caught early.
+[test_load_modules.js]
+
+[test_kinto.js]
+tags = blocklist
+[test_storage_adapter.js]
+tags = remote-settings blocklist
+[test_storage_adapter_shutdown.js]
+tags = remote-settings blocklist
+
+[test_utils_atob.js]
+[test_utils_convert_string.js]
+[test_utils_dateprefs.js]
+[test_utils_encodeBase32.js]
+[test_utils_encodeBase64URL.js]
+[test_utils_ensureMillisecondsTimestamp.js]
+[test_utils_makeURI.js]
+[test_utils_namedTimer.js]
+[test_utils_sets.js]
+[test_utils_utf8.js]
+[test_utils_uuid.js]
+
+[test_async_chain.js]
+[test_async_foreach.js]
+
+[test_hawkclient.js]
+skip-if = os == "android"
+[test_hawkrequest.js]
+skip-if = os == "android"
+
+[test_logmanager.js]
+[test_observers.js]
+[test_restrequest.js]
+
+[test_tokenauthenticatedrequest.js]
+
+[test_tokenserverclient.js]
+skip-if = os == "android"
+
+[test_uptake_telemetry.js]
+tags = remote-settings
diff --git a/services/common/tokenserverclient.sys.mjs b/services/common/tokenserverclient.sys.mjs
new file mode 100644
index 0000000000..c23e3d779c
--- /dev/null
+++ b/services/common/tokenserverclient.sys.mjs
@@ -0,0 +1,392 @@
+/* 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/. */
+
+import { Log } from "resource://gre/modules/Log.sys.mjs";
+
+import { RESTRequest } from "resource://services-common/rest.sys.mjs";
+import { Observers } from "resource://services-common/observers.sys.mjs";
+
+const PREF_LOG_LEVEL = "services.common.log.logger.tokenserverclient";
+
+/**
+ * Represents a TokenServerClient error that occurred on the client.
+ *
+ * This is the base type for all errors raised by client operations.
+ *
+ * @param message
+ *        (string) Error message.
+ */
+export function TokenServerClientError(message) {
+  this.name = "TokenServerClientError";
+  this.message = message || "Client error.";
+  // Without explicitly setting .stack, all stacks from these errors will point
+  // to the "new Error()" call a few lines down, which isn't helpful.
+  this.stack = Error().stack;
+}
+
+TokenServerClientError.prototype = new Error();
+TokenServerClientError.prototype.constructor = TokenServerClientError;
+TokenServerClientError.prototype._toStringFields = function () {
+  return { message: this.message };
+};
+TokenServerClientError.prototype.toString = function () {
+  return this.name + "(" + JSON.stringify(this._toStringFields()) + ")";
+};
+TokenServerClientError.prototype.toJSON = function () {
+  let result = this._toStringFields();
+  result.name = this.name;
+  return result;
+};
+
+/**
+ * Represents a TokenServerClient error that occurred in the network layer.
+ *
+ * @param error
+ *        The underlying error thrown by the network layer.
+ */
+export function TokenServerClientNetworkError(error) {
+  this.name = "TokenServerClientNetworkError";
+  this.error = error;
+  this.stack = Error().stack;
+}
+
+TokenServerClientNetworkError.prototype = new TokenServerClientError();
+TokenServerClientNetworkError.prototype.constructor =
+  TokenServerClientNetworkError;
+TokenServerClientNetworkError.prototype._toStringFields = function () {
+  return { error: this.error };
+};
+
+/**
+ * Represents a TokenServerClient error that occurred on the server.
+ *
+ * This type will be encountered for all non-200 response codes from the
+ * server. The type of error is strongly enumerated and is stored in the
+ * `cause` property. This property can have the following string values:
+ *
+ *   invalid-credentials -- A token could not be obtained because
+ *     the credentials presented by the client were invalid.
+ *
+ *   unknown-service -- The requested service was not found.
+ *
+ *   malformed-request -- The server rejected the request because it
+ *     was invalid. If you see this, code in this file is likely wrong.
+ *
+ *   malformed-response -- The response from the server was not what was
+ *     expected.
+ *
+ *   general -- A general server error has occurred. Clients should
+ *     interpret this as an opaque failure.
+ *
+ * @param message
+ *        (string) Error message.
+ */
+export function TokenServerClientServerError(message, cause = "general") {
+  this.now = new Date().toISOString(); // may be useful to diagnose time-skew issues.
+  this.name = "TokenServerClientServerError";
+  this.message = message || "Server error.";
+  this.cause = cause;
+  this.stack = Error().stack;
+}
+
+TokenServerClientServerError.prototype = new TokenServerClientError();
+TokenServerClientServerError.prototype.constructor =
+  TokenServerClientServerError;
+
+TokenServerClientServerError.prototype._toStringFields = function () {
+  let fields = {
+    now: this.now,
+    message: this.message,
+    cause: this.cause,
+  };
+  if (this.response) {
+    fields.response_body = this.response.body;
+    fields.response_headers = this.response.headers;
+    fields.response_status = this.response.status;
+  }
+  return fields;
+};
+
+/**
+ * Represents a client to the Token Server.
+ *
+ * http://docs.services.mozilla.com/token/index.html
+ *
+ * The Token Server was designed to support obtaining tokens for arbitrary apps by
+ * constructing URI paths of the form <app>/<app_version>. In practice this was
+ * never used and it only supports an <app> value of `sync`, and the API presented
+ * here reflects that.
+ *
+ * Areas to Improve:
+ *
+ *  - The server sends a JSON response on error. The client does not currently
+ *    parse this. It might be convenient if it did.
+ *  - Currently most non-200 status codes are rolled into one error type. It
+ *    might be helpful if callers had a richer API that communicated who was
+ *    at fault (e.g. differentiating a 503 from a 401).
+ */
+export function TokenServerClient() {
+  this._log = Log.repository.getLogger("Services.Common.TokenServerClient");
+  this._log.manageLevelFromPref(PREF_LOG_LEVEL);
+}
+
+TokenServerClient.prototype = {
+  /**
+   * Logger instance.
+   */
+  _log: null,
+
+  /**
+   * Obtain a token from a provided OAuth token against a specific URL.
+   *
+   * This asynchronously obtains the token.
+   * It returns a Promise that resolves or rejects:
+   *
+   *  Rejects with:
+   *   (TokenServerClientError) If no token could be obtained, this
+   *     will be a TokenServerClientError instance describing why. The
+   *     type seen defines the type of error encountered. If an HTTP response
+   *     was seen, a RESTResponse instance will be stored in the `response`
+   *     property of this object. If there was no error and a token is
+   *     available, this will be null.
+   *
+   *  Resolves with:
+   *   (map) On success, this will be a map containing the results from
+   *     the server. If there was an error, this will be null. The map has the
+   *     following properties:
+   *
+   *       id       (string) HTTP MAC public key identifier.
+   *       key      (string) HTTP MAC shared symmetric key.
+   *       endpoint (string) URL where service can be connected to.
+   *       uid      (string) user ID for requested service.
+   *       duration (string) the validity duration of the issued token.
+   *
+   * Example Usage
+   * -------------
+   *
+   *   let client = new TokenServerClient();
+   *   let access_token = getOAuthAccessTokenFromSomewhere();
+   *   let url = "https://token.services.mozilla.com/1.0/sync/2.0";
+   *
+   *   try {
+   *     const result = await client.getTokenUsingOAuth(url, access_token);
+   *     let {id, key, uid, endpoint, duration} = result;
+   *     // Do stuff with data and carry on.
+   *   } catch (error) {
+   *     // Handle errors.
+   *   }
+   * Obtain a token from a provided OAuth token against a specific URL.
+   *
+   * @param  url
+   *         (string) URL to fetch token from.
+   * @param  oauthToken
+   *         (string) FxA OAuth Token to exchange token for.
+   * @param  addHeaders
+   *         (object) Extra headers for the request.
+   */
+  async getTokenUsingOAuth(url, oauthToken, addHeaders = {}) {
+    this._log.debug("Beginning OAuth token exchange: " + url);
+
+    if (!oauthToken) {
+      throw new TokenServerClientError("oauthToken argument is not valid.");
+    }
+
+    return this._tokenServerExchangeRequest(
+      url,
+      `Bearer ${oauthToken}`,
+      addHeaders
+    );
+  },
+
+  /**
+   * Performs the exchange request to the token server to
+   * produce a token based on the authorizationHeader input.
+   *
+   * @param  url
+   *         (string) URL to fetch token from.
+   * @param  authorizationHeader
+   *         (string) The auth header string that populates the 'Authorization' header.
+   * @param  addHeaders
+   *         (object) Extra headers for the request.
+   */
+  async _tokenServerExchangeRequest(url, authorizationHeader, addHeaders = {}) {
+    if (!url) {
+      throw new TokenServerClientError("url argument is not valid.");
+    }
+
+    if (!authorizationHeader) {
+      throw new TokenServerClientError(
+        "authorizationHeader argument is not valid."
+      );
+    }
+
+    let req = this.newRESTRequest(url);
+    req.setHeader("Accept", "application/json");
+    req.setHeader("Authorization", authorizationHeader);
+
+    for (let header in addHeaders) {
+      req.setHeader(header, addHeaders[header]);
+    }
+    let response;
+    try {
+      response = await req.get();
+    } catch (err) {
+      throw new TokenServerClientNetworkError(err);
+    }
+
+    try {
+      return this._processTokenResponse(response);
+    } catch (ex) {
+      if (ex instanceof TokenServerClientServerError) {
+        throw ex;
+      }
+      this._log.warn("Error processing token server response", ex);
+      let error = new TokenServerClientError(ex);
+      error.response = response;
+      throw error;
+    }
+  },
+
+  /**
+   * Handler to process token request responses.
+   *
+   * @param response
+   *        RESTResponse from token HTTP request.
+   */
+  _processTokenResponse(response) {
+    this._log.debug("Got token response: " + response.status);
+
+    // Responses should *always* be JSON, even in the case of 4xx and 5xx
+    // errors. If we don't see JSON, the server is likely very unhappy.
+    let ct = response.headers["content-type"] || "";
+    if (ct != "application/json" && !ct.startsWith("application/json;")) {
+      this._log.warn("Did not receive JSON response. Misconfigured server?");
+      this._log.debug("Content-Type: " + ct);
+      this._log.debug("Body: " + response.body);
+
+      let error = new TokenServerClientServerError(
+        "Non-JSON response.",
+        "malformed-response"
+      );
+      error.response = response;
+      throw error;
+    }
+
+    let result;
+    try {
+      result = JSON.parse(response.body);
+    } catch (ex) {
+      this._log.warn("Invalid JSON returned by server: " + response.body);
+      let error = new TokenServerClientServerError(
+        "Malformed JSON.",
+        "malformed-response"
+      );
+      error.response = response;
+      throw error;
+    }
+
+    // Any response status can have X-Backoff or X-Weave-Backoff headers.
+    this._maybeNotifyBackoff(response, "x-weave-backoff");
+    this._maybeNotifyBackoff(response, "x-backoff");
+
+    // The service shouldn't have any 3xx, so we don't need to handle those.
+    if (response.status != 200) {
+      // We /should/ have a Cornice error report in the JSON. We log that to
+      // help with debugging.
+      if ("errors" in result) {
+        // This could throw, but this entire function is wrapped in a try. If
+        // the server is sending something not an array of objects, it has
+        // failed to keep its contract with us and there is little we can do.
+        for (let error of result.errors) {
+          this._log.info("Server-reported error: " + JSON.stringify(error));
+        }
+      }
+
+      let error = new TokenServerClientServerError();
+      error.response = response;
+
+      if (response.status == 400) {
+        error.message = "Malformed request.";
+        error.cause = "malformed-request";
+      } else if (response.status == 401) {
+        // Cause can be invalid-credentials, invalid-timestamp, or
+        // invalid-generation.
+        error.message = "Authentication failed.";
+        error.cause = result.status;
+      } else if (response.status == 404) {
+        error.message = "Unknown service.";
+        error.cause = "unknown-service";
+      }
+
+      // A Retry-After header should theoretically only appear on a 503, but
+      // we'll look for it on any error response.
+      this._maybeNotifyBackoff(response, "retry-after");
+
+      throw error;
+    }
+
+    for (let k of ["id", "key", "api_endpoint", "uid", "duration"]) {
+      if (!(k in result)) {
+        let error = new TokenServerClientServerError(
+          "Expected key not present in result: " + k
+        );
+        error.cause = "malformed-response";
+        error.response = response;
+        throw error;
+      }
+    }
+
+    this._log.debug("Successful token response");
+    return {
+      id: result.id,
+      key: result.key,
+      endpoint: result.api_endpoint,
+      uid: result.uid,
+      duration: result.duration,
+      hashed_fxa_uid: result.hashed_fxa_uid,
+      node_type: result.node_type,
+    };
+  },
+
+  /*
+   * The prefix used for all notifications sent by this module.  This
+   * allows the handler of notifications to be sure they are handling
+   * notifications for the service they expect.
+   *
+   * If not set, no notifications will be sent.
+   */
+  observerPrefix: null,
+
+  // Given an optional header value, notify that a backoff has been requested.
+  _maybeNotifyBackoff(response, headerName) {
+    if (!this.observerPrefix) {
+      return;
+    }
+    let headerVal = response.headers[headerName];
+    if (!headerVal) {
+      return;
+    }
+    let backoffInterval;
+    try {
+      backoffInterval = parseInt(headerVal, 10);
+    } catch (ex) {
+      this._log.error(
+        "TokenServer response had invalid backoff value in '" +
+          headerName +
+          "' header: " +
+          headerVal
+      );
+      return;
+    }
+    Observers.notify(
+      this.observerPrefix + ":backoff:interval",
+      backoffInterval
+    );
+  },
+
+  // override points for testing.
+  newRESTRequest(url) {
+    return new RESTRequest(url);
+  },
+};
diff --git a/services/common/uptake-telemetry.sys.mjs b/services/common/uptake-telemetry.sys.mjs
new file mode 100644
index 0000000000..9900f548fd
--- /dev/null
+++ b/services/common/uptake-telemetry.sys.mjs
@@ -0,0 +1,193 @@
+/* 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/. */
+
+import { XPCOMUtils } from "resource://gre/modules/XPCOMUtils.sys.mjs";
+import { AppConstants } from "resource://gre/modules/AppConstants.sys.mjs";
+
+const lazy = {};
+ChromeUtils.defineESModuleGetters(lazy, {
+  ClientID: "resource://gre/modules/ClientID.sys.mjs",
+});
+
+XPCOMUtils.defineLazyGetter(lazy, "CryptoHash", () => {
+  return Components.Constructor(
+    "@mozilla.org/security/hash;1",
+    "nsICryptoHash",
+    "initWithString"
+  );
+});
+
+XPCOMUtils.defineLazyPreferenceGetter(
+  lazy,
+  "gSampleRate",
+  "services.common.uptake.sampleRate"
+);
+
+// Telemetry events id (see Events.yaml).
+const TELEMETRY_EVENTS_ID = "uptake.remotecontent.result";
+
+/**
+ * A wrapper around certain low-level operations that can be substituted for testing.
+ */
+export var Policy = {
+  _clientIDHash: null,
+
+  getClientID() {
+    return lazy.ClientID.getClientID();
+  },
+
+  /**
+   * Compute an integer in the range [0, 100) using a hash of the
+   * client ID.
+   *
+   * This is useful for sampling clients when trying to report
+   * telemetry only for a sample of clients.
+   */
+  async getClientIDHash() {
+    if (this._clientIDHash === null) {
+      this._clientIDHash = this._doComputeClientIDHash();
+    }
+    return this._clientIDHash;
+  },
+
+  async _doComputeClientIDHash() {
+    const clientID = await this.getClientID();
+    let byteArr = new TextEncoder().encode(clientID);
+    let hash = new lazy.CryptoHash("sha256");
+    hash.update(byteArr, byteArr.length);
+    const bytes = hash.finish(false);
+    let rem = 0;
+    for (let i = 0, len = bytes.length; i < len; i++) {
+      rem = ((rem << 8) + (bytes[i].charCodeAt(0) & 0xff)) % 100;
+    }
+    return rem;
+  },
+
+  getChannel() {
+    return AppConstants.MOZ_UPDATE_CHANNEL;
+  },
+};
+
+/**
+ * A Telemetry helper to report uptake of remote content.
+ */
+export class UptakeTelemetry {
+  /**
+   * Supported uptake statuses:
+   *
+   * - `UP_TO_DATE`: Local content was already up-to-date with remote content.
+   * - `SUCCESS`: Local content was updated successfully.
+   * - `BACKOFF`: Remote server asked clients to backoff.
+   * - `PARSE_ERROR`: Parsing server response has failed.
+   * - `CONTENT_ERROR`: Server response has unexpected content.
+   * - `PREF_DISABLED`: Update is disabled in user preferences.
+   * - `SIGNATURE_ERROR`: Signature verification after diff-based sync has failed.
+   * - `SIGNATURE_RETRY_ERROR`: Signature verification after full fetch has failed.
+   * - `CONFLICT_ERROR`: Some remote changes are in conflict with local changes.
+   * - `CORRUPTION_ERROR`: Error related to corrupted local data.
+   * - `SYNC_ERROR`: Synchronization of remote changes has failed.
+   * - `APPLY_ERROR`: Application of changes locally has failed.
+   * - `SERVER_ERROR`: Server failed to respond.
+   * - `CERTIFICATE_ERROR`: Server certificate verification has failed.
+   * - `DOWNLOAD_ERROR`: Data could not be fully retrieved.
+   * - `TIMEOUT_ERROR`: Server response has timed out.
+   * - `NETWORK_ERROR`: Communication with server has failed.
+   * - `NETWORK_OFFLINE_ERROR`: Network not available.
+   * - `SHUTDOWN_ERROR`: Error occuring during shutdown.
+   * - `UNKNOWN_ERROR`: Uncategorized error.
+   * - `CLEANUP_ERROR`: Clean-up of temporary files has failed.
+   * - `SYNC_BROKEN_ERROR`: Synchronization is broken.
+   * - `CUSTOM_1_ERROR`: Update source specific error #1.
+   * - `CUSTOM_2_ERROR`: Update source specific error #2.
+   * - `CUSTOM_3_ERROR`: Update source specific error #3.
+   * - `CUSTOM_4_ERROR`: Update source specific error #4.
+   * - `CUSTOM_5_ERROR`: Update source specific error #5.
+   *
+   * @type {Object}
+   */
+  static get STATUS() {
+    return {
+      UP_TO_DATE: "up_to_date",
+      SUCCESS: "success",
+      BACKOFF: "backoff",
+      PARSE_ERROR: "parse_error",
+      CONTENT_ERROR: "content_error",
+      PREF_DISABLED: "pref_disabled",
+      SIGNATURE_ERROR: "sign_error",
+      SIGNATURE_RETRY_ERROR: "sign_retry_error",
+      CONFLICT_ERROR: "conflict_error",
+      CORRUPTION_ERROR: "corruption_error",
+      SYNC_ERROR: "sync_error",
+      APPLY_ERROR: "apply_error",
+      SERVER_ERROR: "server_error",
+      CERTIFICATE_ERROR: "certificate_error",
+      DOWNLOAD_ERROR: "download_error",
+      TIMEOUT_ERROR: "timeout_error",
+      NETWORK_ERROR: "network_error",
+      NETWORK_OFFLINE_ERROR: "offline_error",
+      SHUTDOWN_ERROR: "shutdown_error",
+      UNKNOWN_ERROR: "unknown_error",
+      CLEANUP_ERROR: "cleanup_error",
+      SYNC_BROKEN_ERROR: "sync_broken_error",
+      CUSTOM_1_ERROR: "custom_1_error",
+      CUSTOM_2_ERROR: "custom_2_error",
+      CUSTOM_3_ERROR: "custom_3_error",
+      CUSTOM_4_ERROR: "custom_4_error",
+      CUSTOM_5_ERROR: "custom_5_error",
+    };
+  }
+
+  static get Policy() {
+    return Policy;
+  }
+
+  /**
+   * Reports the uptake status for the specified source.
+   *
+   * @param {string} component     the component reporting the uptake (eg. "normandy").
+   * @param {string} status        the uptake status (eg. "network_error")
+   * @param {Object} extra         extra values to report
+   * @param {string} extra.source  the update source (eg. "recipe-42").
+   * @param {string} extra.trigger what triggered the polling/fetching (eg. "broadcast", "timer").
+   * @param {int}    extra.age     age of pulled data in seconds
+   */
+  static async report(component, status, extra = {}) {
+    const { source } = extra;
+
+    if (!source) {
+      throw new Error("`source` value is mandatory.");
+    }
+
+    if (!Object.values(UptakeTelemetry.STATUS).includes(status)) {
+      throw new Error(`Unknown status '${status}'`);
+    }
+
+    // Report event for real-time monitoring. See Events.yaml for registration.
+    // Contrary to histograms, Telemetry Events are not enabled by default.
+    // Enable them on first call to `report()`.
+    if (!this._eventsEnabled) {
+      Services.telemetry.setEventRecordingEnabled(TELEMETRY_EVENTS_ID, true);
+      this._eventsEnabled = true;
+    }
+
+    const hash = await UptakeTelemetry.Policy.getClientIDHash();
+    const channel = UptakeTelemetry.Policy.getChannel();
+    const shouldSendEvent =
+      !["release", "esr"].includes(channel) || hash < lazy.gSampleRate;
+    if (shouldSendEvent) {
+      // The Event API requires `extra` values to be of type string. Force it!
+      const extraStr = Object.keys(extra).reduce((acc, k) => {
+        acc[k] = extra[k].toString();
+        return acc;
+      }, {});
+      Services.telemetry.recordEvent(
+        TELEMETRY_EVENTS_ID,
+        "uptake",
+        component,
+        status,
+        extraStr
+      );
+    }
+  }
+}
diff --git a/services/common/utils.sys.mjs b/services/common/utils.sys.mjs
new file mode 100644
index 0000000000..3c7f9f9d39
--- /dev/null
+++ b/services/common/utils.sys.mjs
@@ -0,0 +1,695 @@
+/* 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/. */
+
+import { XPCOMUtils } from "resource://gre/modules/XPCOMUtils.sys.mjs";
+
+import { Log } from "resource://gre/modules/Log.sys.mjs";
+
+export var CommonUtils = {
+  /*
+   * Set manipulation methods. These should be lifted into toolkit, or added to
+   * `Set` itself.
+   */
+
+  /**
+   * Return elements of `a` or `b`.
+   */
+  union(a, b) {
+    let out = new Set(a);
+    for (let x of b) {
+      out.add(x);
+    }
+    return out;
+  },
+
+  /**
+   * Return elements of `a` that are not present in `b`.
+   */
+  difference(a, b) {
+    let out = new Set(a);
+    for (let x of b) {
+      out.delete(x);
+    }
+    return out;
+  },
+
+  /**
+   * Return elements of `a` that are also in `b`.
+   */
+  intersection(a, b) {
+    let out = new Set();
+    for (let x of a) {
+      if (b.has(x)) {
+        out.add(x);
+      }
+    }
+    return out;
+  },
+
+  /**
+   * Return true if `a` and `b` are the same size, and
+   * every element of `a` is in `b`.
+   */
+  setEqual(a, b) {
+    if (a.size != b.size) {
+      return false;
+    }
+    for (let x of a) {
+      if (!b.has(x)) {
+        return false;
+      }
+    }
+    return true;
+  },
+
+  /**
+   * Checks elements in two arrays for equality, as determined by the `===`
+   * operator. This function does not perform a deep comparison; see Sync's
+   * `Util.deepEquals` for that.
+   */
+  arrayEqual(a, b) {
+    if (a.length !== b.length) {
+      return false;
+    }
+    for (let i = 0; i < a.length; i++) {
+      if (a[i] !== b[i]) {
+        return false;
+      }
+    }
+    return true;
+  },
+
+  /**
+   * Encode byte string as base64URL (RFC 4648).
+   *
+   * @param bytes
+   *        (string) Raw byte string to encode.
+   * @param pad
+   *        (bool) Whether to include padding characters (=). Defaults
+   *        to true for historical reasons.
+   */
+  encodeBase64URL: function encodeBase64URL(bytes, pad = true) {
+    let s = btoa(bytes).replace(/\+/g, "-").replace(/\//g, "_");
+
+    if (!pad) {
+      return s.replace(/=+$/, "");
+    }
+
+    return s;
+  },
+
+  /**
+   * Create a nsIURI instance from a string.
+   */
+  makeURI: function makeURI(URIString) {
+    if (!URIString) {
+      return null;
+    }
+    try {
+      return Services.io.newURI(URIString);
+    } catch (e) {
+      let log = Log.repository.getLogger("Common.Utils");
+      log.debug("Could not create URI", e);
+      return null;
+    }
+  },
+
+  /**
+   * Execute a function on the next event loop tick.
+   *
+   * @param callback
+   *        Function to invoke.
+   * @param thisObj [optional]
+   *        Object to bind the callback to.
+   */
+  nextTick: function nextTick(callback, thisObj) {
+    if (thisObj) {
+      callback = callback.bind(thisObj);
+    }
+    Services.tm.dispatchToMainThread(callback);
+  },
+
+  /**
+   * Return a timer that is scheduled to call the callback after waiting the
+   * provided time or as soon as possible. The timer will be set as a property
+   * of the provided object with the given timer name.
+   */
+  namedTimer: function namedTimer(callback, wait, thisObj, name) {
+    if (!thisObj || !name) {
+      throw new Error(
+        "You must provide both an object and a property name for the timer!"
+      );
+    }
+
+    // Delay an existing timer if it exists
+    if (name in thisObj && thisObj[name] instanceof Ci.nsITimer) {
+      thisObj[name].delay = wait;
+      return thisObj[name];
+    }
+
+    // Create a special timer that we can add extra properties
+    let timer = Object.create(
+      Cc["@mozilla.org/timer;1"].createInstance(Ci.nsITimer)
+    );
+
+    // Provide an easy way to clear out the timer
+    timer.clear = function () {
+      thisObj[name] = null;
+      timer.cancel();
+    };
+
+    // Initialize the timer with a smart callback
+    timer.initWithCallback(
+      {
+        notify: function notify() {
+          // Clear out the timer once it's been triggered
+          timer.clear();
+          callback.call(thisObj, timer);
+        },
+      },
+      wait,
+      timer.TYPE_ONE_SHOT
+    );
+
+    return (thisObj[name] = timer);
+  },
+
+  encodeUTF8: function encodeUTF8(str) {
+    try {
+      str = this._utf8Converter.ConvertFromUnicode(str);
+      return str + this._utf8Converter.Finish();
+    } catch (ex) {
+      return null;
+    }
+  },
+
+  decodeUTF8: function decodeUTF8(str) {
+    try {
+      str = this._utf8Converter.ConvertToUnicode(str);
+      return str + this._utf8Converter.Finish();
+    } catch (ex) {
+      return null;
+    }
+  },
+
+  byteArrayToString: function byteArrayToString(bytes) {
+    return bytes.map(byte => String.fromCharCode(byte)).join("");
+  },
+
+  stringToByteArray: function stringToByteArray(bytesString) {
+    return Array.prototype.slice.call(bytesString).map(c => c.charCodeAt(0));
+  },
+
+  // A lot of Util methods work with byte strings instead of ArrayBuffers.
+  // A patch should address this problem, but in the meantime let's provide
+  // helpers method to convert byte strings to Uint8Array.
+  byteStringToArrayBuffer(byteString) {
+    if (byteString === undefined) {
+      return new Uint8Array();
+    }
+    const bytes = new Uint8Array(byteString.length);
+    for (let i = 0; i < byteString.length; ++i) {
+      bytes[i] = byteString.charCodeAt(i) & 0xff;
+    }
+    return bytes;
+  },
+
+  arrayBufferToByteString(buffer) {
+    return CommonUtils.byteArrayToString([...buffer]);
+  },
+
+  bufferToHex(buffer) {
+    return Array.prototype.map
+      .call(buffer, x => ("00" + x.toString(16)).slice(-2))
+      .join("");
+  },
+
+  bytesAsHex: function bytesAsHex(bytes) {
+    let s = "";
+    for (let i = 0, len = bytes.length; i < len; i++) {
+      let c = (bytes[i].charCodeAt(0) & 0xff).toString(16);
+      if (c.length == 1) {
+        c = "0" + c;
+      }
+      s += c;
+    }
+    return s;
+  },
+
+  stringAsHex: function stringAsHex(str) {
+    return CommonUtils.bytesAsHex(CommonUtils.encodeUTF8(str));
+  },
+
+  stringToBytes: function stringToBytes(str) {
+    return CommonUtils.hexToBytes(CommonUtils.stringAsHex(str));
+  },
+
+  hexToBytes: function hexToBytes(str) {
+    let bytes = [];
+    for (let i = 0; i < str.length - 1; i += 2) {
+      bytes.push(parseInt(str.substr(i, 2), 16));
+    }
+    return String.fromCharCode.apply(String, bytes);
+  },
+
+  hexToArrayBuffer(str) {
+    const octString = CommonUtils.hexToBytes(str);
+    return CommonUtils.byteStringToArrayBuffer(octString);
+  },
+
+  hexAsString: function hexAsString(hex) {
+    return CommonUtils.decodeUTF8(CommonUtils.hexToBytes(hex));
+  },
+
+  base64urlToHex(b64str) {
+    return CommonUtils.bufferToHex(
+      new Uint8Array(ChromeUtils.base64URLDecode(b64str, { padding: "reject" }))
+    );
+  },
+
+  /**
+   * Base32 encode (RFC 4648) a string
+   */
+  encodeBase32: function encodeBase32(bytes) {
+    const key = "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567";
+    let leftover = bytes.length % 5;
+
+    // Pad the last quantum with zeros so the length is a multiple of 5.
+    if (leftover) {
+      for (let i = leftover; i < 5; i++) {
+        bytes += "\0";
+      }
+    }
+
+    // Chop the string into quanta of 5 bytes (40 bits). Each quantum
+    // is turned into 8 characters from the 32 character base.
+    let ret = "";
+    for (let i = 0; i < bytes.length; i += 5) {
+      let c = Array.prototype.slice
+        .call(bytes.slice(i, i + 5))
+        .map(byte => byte.charCodeAt(0));
+      ret +=
+        key[c[0] >> 3] +
+        key[((c[0] << 2) & 0x1f) | (c[1] >> 6)] +
+        key[(c[1] >> 1) & 0x1f] +
+        key[((c[1] << 4) & 0x1f) | (c[2] >> 4)] +
+        key[((c[2] << 1) & 0x1f) | (c[3] >> 7)] +
+        key[(c[3] >> 2) & 0x1f] +
+        key[((c[3] << 3) & 0x1f) | (c[4] >> 5)] +
+        key[c[4] & 0x1f];
+    }
+
+    switch (leftover) {
+      case 1:
+        return ret.slice(0, -6) + "======";
+      case 2:
+        return ret.slice(0, -4) + "====";
+      case 3:
+        return ret.slice(0, -3) + "===";
+      case 4:
+        return ret.slice(0, -1) + "=";
+      default:
+        return ret;
+    }
+  },
+
+  /**
+   * Base32 decode (RFC 4648) a string.
+   */
+  decodeBase32: function decodeBase32(str) {
+    const key = "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567";
+
+    let padChar = str.indexOf("=");
+    let chars = padChar == -1 ? str.length : padChar;
+    let bytes = Math.floor((chars * 5) / 8);
+    let blocks = Math.ceil(chars / 8);
+
+    // Process a chunk of 5 bytes / 8 characters.
+    // The processing of this is known in advance,
+    // so avoid arithmetic!
+    function processBlock(ret, cOffset, rOffset) {
+      let c, val;
+
+      // N.B., this relies on
+      //   undefined | foo == foo.
+      function accumulate(val) {
+        ret[rOffset] |= val;
+      }
+
+      function advance() {
+        c = str[cOffset++];
+        if (!c || c == "" || c == "=") {
+          // Easier than range checking.
+          throw new Error("Done");
+        } // Will be caught far away.
+        val = key.indexOf(c);
+        if (val == -1) {
+          throw new Error(`Unknown character in base32: ${c}`);
+        }
+      }
+
+      // Handle a left shift, restricted to bytes.
+      function left(octet, shift) {
+        return (octet << shift) & 0xff;
+      }
+
+      advance();
+      accumulate(left(val, 3));
+      advance();
+      accumulate(val >> 2);
+      ++rOffset;
+      accumulate(left(val, 6));
+      advance();
+      accumulate(left(val, 1));
+      advance();
+      accumulate(val >> 4);
+      ++rOffset;
+      accumulate(left(val, 4));
+      advance();
+      accumulate(val >> 1);
+      ++rOffset;
+      accumulate(left(val, 7));
+      advance();
+      accumulate(left(val, 2));
+      advance();
+      accumulate(val >> 3);
+      ++rOffset;
+      accumulate(left(val, 5));
+      advance();
+      accumulate(val);
+      ++rOffset;
+    }
+
+    // Our output. Define to be explicit (and maybe the compiler will be smart).
+    let ret = new Array(bytes);
+    let i = 0;
+    let cOff = 0;
+    let rOff = 0;
+
+    for (; i < blocks; ++i) {
+      try {
+        processBlock(ret, cOff, rOff);
+      } catch (ex) {
+        // Handle the detection of padding.
+        if (ex.message == "Done") {
+          break;
+        }
+        throw ex;
+      }
+      cOff += 8;
+      rOff += 5;
+    }
+
+    // Slice in case our shift overflowed to the right.
+    return CommonUtils.byteArrayToString(ret.slice(0, bytes));
+  },
+
+  /**
+   * Trim excess padding from a Base64 string and atob().
+   *
+   * See bug 562431 comment 4.
+   */
+  safeAtoB: function safeAtoB(b64) {
+    let len = b64.length;
+    let over = len % 4;
+    return over ? atob(b64.substr(0, len - over)) : atob(b64);
+  },
+
+  /**
+   * Ensure that the specified value is defined in integer milliseconds since
+   * UNIX epoch.
+   *
+   * This throws an error if the value is not an integer, is negative, or looks
+   * like seconds, not milliseconds.
+   *
+   * If the value is null or 0, no exception is raised.
+   *
+   * @param value
+   *        Value to validate.
+   */
+  ensureMillisecondsTimestamp: function ensureMillisecondsTimestamp(value) {
+    if (!value) {
+      return;
+    }
+
+    if (!/^[0-9]+$/.test(value)) {
+      throw new Error("Timestamp value is not a positive integer: " + value);
+    }
+
+    let intValue = parseInt(value, 10);
+
+    if (!intValue) {
+      return;
+    }
+
+    // Catch what looks like seconds, not milliseconds.
+    if (intValue < 10000000000) {
+      throw new Error("Timestamp appears to be in seconds: " + intValue);
+    }
+  },
+
+  /**
+   * Read bytes from an nsIInputStream into a string.
+   *
+   * @param stream
+   *        (nsIInputStream) Stream to read from.
+   * @param count
+   *        (number) Integer number of bytes to read. If not defined, or
+   *        0, all available input is read.
+   */
+  readBytesFromInputStream: function readBytesFromInputStream(stream, count) {
+    let BinaryInputStream = Components.Constructor(
+      "@mozilla.org/binaryinputstream;1",
+      "nsIBinaryInputStream",
+      "setInputStream"
+    );
+    if (!count) {
+      count = stream.available();
+    }
+
+    return new BinaryInputStream(stream).readBytes(count);
+  },
+
+  /**
+   * Generate a new UUID using nsIUUIDGenerator.
+   *
+   * Example value: "1e00a2e2-1570-443e-bf5e-000354124234"
+   *
+   * @return string A hex-formatted UUID string.
+   */
+  generateUUID: function generateUUID() {
+    let uuid = Services.uuid.generateUUID().toString();
+
+    return uuid.substring(1, uuid.length - 1);
+  },
+
+  /**
+   * Obtain an epoch value from a preference.
+   *
+   * This reads a string preference and returns an integer. The string
+   * preference is expected to contain the integer milliseconds since epoch.
+   * For best results, only read preferences that have been saved with
+   * setDatePref().
+   *
+   * We need to store times as strings because integer preferences are only
+   * 32 bits and likely overflow most dates.
+   *
+   * If the pref contains a non-integer value, the specified default value will
+   * be returned.
+   *
+   * @param branch
+   *        (Preferences) Branch from which to retrieve preference.
+   * @param pref
+   *        (string) The preference to read from.
+   * @param def
+   *        (Number) The default value to use if the preference is not defined.
+   * @param log
+   *        (Log.Logger) Logger to write warnings to.
+   */
+  getEpochPref: function getEpochPref(branch, pref, def = 0, log = null) {
+    if (!Number.isInteger(def)) {
+      throw new Error("Default value is not a number: " + def);
+    }
+
+    let valueStr = branch.get(pref, null);
+
+    if (valueStr !== null) {
+      let valueInt = parseInt(valueStr, 10);
+      if (Number.isNaN(valueInt)) {
+        if (log) {
+          log.warn(
+            "Preference value is not an integer. Using default. " +
+              pref +
+              "=" +
+              valueStr +
+              " -> " +
+              def
+          );
+        }
+
+        return def;
+      }
+
+      return valueInt;
+    }
+
+    return def;
+  },
+
+  /**
+   * Obtain a Date from a preference.
+   *
+   * This is a wrapper around getEpochPref. It converts the value to a Date
+   * instance and performs simple range checking.
+   *
+   * The range checking ensures the date is newer than the oldestYear
+   * parameter.
+   *
+   * @param branch
+   *        (Preferences) Branch from which to read preference.
+   * @param pref
+   *        (string) The preference from which to read.
+   * @param def
+   *        (Number) The default value (in milliseconds) if the preference is
+   *        not defined or invalid.
+   * @param log
+   *        (Log.Logger) Logger to write warnings to.
+   * @param oldestYear
+   *        (Number) Oldest year to accept in read values.
+   */
+  getDatePref: function getDatePref(
+    branch,
+    pref,
+    def = 0,
+    log = null,
+    oldestYear = 2010
+  ) {
+    let valueInt = this.getEpochPref(branch, pref, def, log);
+    let date = new Date(valueInt);
+
+    if (valueInt == def || date.getFullYear() >= oldestYear) {
+      return date;
+    }
+
+    if (log) {
+      log.warn(
+        "Unexpected old date seen in pref. Returning default: " +
+          pref +
+          "=" +
+          date +
+          " -> " +
+          def
+      );
+    }
+
+    return new Date(def);
+  },
+
+  /**
+   * Store a Date in a preference.
+   *
+   * This is the opposite of getDatePref(). The same notes apply.
+   *
+   * If the range check fails, an Error will be thrown instead of a default
+   * value silently being used.
+   *
+   * @param branch
+   *        (Preference) Branch from which to read preference.
+   * @param pref
+   *        (string) Name of preference to write to.
+   * @param date
+   *        (Date) The value to save.
+   * @param oldestYear
+   *        (Number) The oldest year to accept for values.
+   */
+  setDatePref: function setDatePref(branch, pref, date, oldestYear = 2010) {
+    if (date.getFullYear() < oldestYear) {
+      throw new Error(
+        "Trying to set " +
+          pref +
+          " to a very old time: " +
+          date +
+          ". The current time is " +
+          new Date() +
+          ". Is the system clock wrong?"
+      );
+    }
+
+    branch.set(pref, "" + date.getTime());
+  },
+
+  /**
+   * Convert a string between two encodings.
+   *
+   * Output is only guaranteed if the input stream is composed of octets. If
+   * the input string has characters with values larger than 255, data loss
+   * will occur.
+   *
+   * The returned string is guaranteed to consist of character codes no greater
+   * than 255.
+   *
+   * @param s
+   *        (string) The source string to convert.
+   * @param source
+   *        (string) The current encoding of the string.
+   * @param dest
+   *        (string) The target encoding of the string.
+   *
+   * @return string
+   */
+  convertString: function convertString(s, source, dest) {
+    if (!s) {
+      throw new Error("Input string must be defined.");
+    }
+
+    let is = Cc["@mozilla.org/io/string-input-stream;1"].createInstance(
+      Ci.nsIStringInputStream
+    );
+    is.setData(s, s.length);
+
+    let listener = Cc["@mozilla.org/network/stream-loader;1"].createInstance(
+      Ci.nsIStreamLoader
+    );
+
+    let result;
+
+    listener.init({
+      onStreamComplete: function onStreamComplete(
+        loader,
+        context,
+        status,
+        length,
+        data
+      ) {
+        result = String.fromCharCode.apply(this, data);
+      },
+    });
+
+    let converter = this._converterService.asyncConvertData(
+      source,
+      dest,
+      listener,
+      null
+    );
+    converter.onStartRequest(null, null);
+    converter.onDataAvailable(null, is, 0, s.length);
+    converter.onStopRequest(null, null, null);
+
+    return result;
+  },
+};
+
+XPCOMUtils.defineLazyGetter(CommonUtils, "_utf8Converter", function () {
+  let converter = Cc[
+    "@mozilla.org/intl/scriptableunicodeconverter"
+  ].createInstance(Ci.nsIScriptableUnicodeConverter);
+  converter.charset = "UTF-8";
+  return converter;
+});
+
+XPCOMUtils.defineLazyGetter(CommonUtils, "_converterService", function () {
+  return Cc["@mozilla.org/streamConverters;1"].getService(
+    Ci.nsIStreamConverterService
+  );
+});