deleted file mode 100644
--- a/xpcom/libxpcomrt/XPCOMRTInit.cpp
+++ /dev/null
@@ -1,199 +0,0 @@
-/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
-/* vim:set ts=4 sw=4 sts=4 ci et: */
-/* 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/. */
-
-#include "mozilla/Module.h"
-#include "mozilla/ModuleUtils.h"
-#include "mozilla/NullPtr.h"
-#include "mozilla/TimeStamp.h"
-#include "nsCategoryManager.h"
-#include "nsComponentManager.h"
-#include "nsDebugImpl.h"
-#include "nsIErrorService.h"
-#include "nsMemoryImpl.h"
-#include "nsNetCID.h"
-#include "nsNetModuleStandalone.h"
-#include "nsObserverService.h"
-#include "nsThreadManager.h"
-#include "nsThreadPool.h"
-#include "nsUUIDGenerator.h"
-#include "nsXPCOMCIDInternal.h"
-#include "nsXPCOMPrivate.h"
-#include "TimerThread.h"
-#include "XPCOMRTInit.h"
-
-static NS_DEFINE_CID(kComponentManagerCID, NS_COMPONENTMANAGER_CID);
-
-NS_GENERIC_FACTORY_CONSTRUCTOR(nsTimerImpl)
-NS_GENERIC_FACTORY_CONSTRUCTOR_INIT(nsUUIDGenerator, Init)
-
-static nsresult
-nsThreadManagerGetSingleton(nsISupports* aOuter,
-                            const nsIID& aIID,
-                            void** aInstancePtr)
-{
-  NS_ASSERTION(aInstancePtr, "null outptr");
-  if (NS_WARN_IF(aOuter)) {
-    return NS_ERROR_NO_AGGREGATION;
-  }
-
-  return nsThreadManager::get()->QueryInterface(aIID, aInstancePtr);
-}
-
-NS_GENERIC_FACTORY_CONSTRUCTOR(nsThreadPool)
-
-nsComponentManagerImpl* nsComponentManagerImpl::gComponentManager = nullptr;
-bool gXPCOMShuttingDown = false;
-bool gXPCOMThreadsShutDown = false;
-
-#define COMPONENT(NAME, Ctor) static NS_DEFINE_CID(kNS_##NAME##_CID, NS_##NAME##_CID);
-#include "XPCOMRTModule.inc"
-#undef COMPONENT
-
-#define COMPONENT(NAME, Ctor) { &kNS_##NAME##_CID, false, nullptr, Ctor },
-const mozilla::Module::CIDEntry kXPCOMCIDEntries[] = {
-  { &kComponentManagerCID, true, nullptr, nsComponentManagerImpl::Create },
-#include "XPCOMRTModule.inc"
-  { nullptr }
-};
-#undef COMPONENT
-
-#define COMPONENT(NAME, Ctor) { NS_##NAME##_CONTRACTID, &kNS_##NAME##_CID },
-const mozilla::Module::ContractIDEntry kXPCOMContracts[] = {
-#include "XPCOMRTModule.inc"
-  { nullptr }
-};
-#undef COMPONENT
-
-const mozilla::Module kXPCOMRTModule = {
-  mozilla::Module::kVersion, kXPCOMCIDEntries, kXPCOMContracts
-};
-
-nsresult
-NS_InitXPCOMRT()
-{
-  nsresult rv = NS_OK;
-
-  NS_SetMainThread();
-
-  mozilla::TimeStamp::Startup();
-
-  rv = nsThreadManager::get()->Init();
-  if (NS_WARN_IF(NS_FAILED(rv))) {
-    return rv;
-  }
-
-  // Set up the timer globals/timer thread
-  rv = nsTimerImpl::Startup();
-  if (NS_WARN_IF(NS_FAILED(rv))) {
-    return rv;
-  }
-
-  nsComponentManagerImpl::gComponentManager = new nsComponentManagerImpl();
-  NS_ADDREF(nsComponentManagerImpl::gComponentManager);
-
-  rv = nsComponentManagerImpl::gComponentManager->Init();
-  if (NS_FAILED(rv)) {
-    NS_RELEASE(nsComponentManagerImpl::gComponentManager);
-    return rv;
-  }
-
-  mozilla::InitNetModuleStandalone();
-
-  return NS_OK;
-}
-
-nsresult
-NS_ShutdownXPCOMRT()
-{
-  nsresult rv = NS_OK;
-
-  // Notify observers of xpcom shutting down
-  {
-    // Block it so that the COMPtr will get deleted before we hit
-    // servicemanager shutdown
-
-    nsCOMPtr<nsIThread> thread = do_GetCurrentThread();
-
-    if (NS_WARN_IF(!thread)) {
-      return NS_ERROR_UNEXPECTED;
-    }
-
-    RefPtr<nsObserverService> observerService;
-    CallGetService("@mozilla.org/observer-service;1",
-                     (nsObserverService**)getter_AddRefs(observerService));
-
-    if (observerService) {
-      observerService->NotifyObservers(nullptr,
-                                       NS_XPCOM_WILL_SHUTDOWN_OBSERVER_ID,
-                                       nullptr);
-
-      nsCOMPtr<nsIServiceManager> mgr;
-      rv = NS_GetServiceManager(getter_AddRefs(mgr));
-      if (NS_SUCCEEDED(rv)) {
-        observerService->NotifyObservers(mgr, NS_XPCOM_SHUTDOWN_OBSERVER_ID,
-                                         nullptr);
-      }
-    }
-
-    // This must happen after the shutdown of media and widgets, which
-    // are triggered by the NS_XPCOM_SHUTDOWN_OBSERVER_ID notification.
-    NS_ProcessPendingEvents(thread);
-
-    if (observerService)
-      observerService->NotifyObservers(nullptr,
-                                       NS_XPCOM_SHUTDOWN_THREADS_OBSERVER_ID,
-                                       nullptr);
-
-    gXPCOMThreadsShutDown = true;
-    NS_ProcessPendingEvents(thread);
-
-    // Shutdown the timer thread and all timers that might still be alive before
-    // shutting down the component manager
-    nsTimerImpl::Shutdown();
-
-    NS_ProcessPendingEvents(thread);
-
-    // Net module needs to be shutdown before the thread manager or else
-    // the thread manager will hang waiting for the socket transport
-    // service to shutdown.
-    mozilla::ShutdownNetModuleStandalone();
-
-    // Shutdown all remaining threads.  This method does not return until
-    // all threads created using the thread manager (with the exception of
-    // the main thread) have exited.
-    nsThreadManager::get()->Shutdown();
-
-    NS_ProcessPendingEvents(thread);
-  }
-
-  mozilla::services::Shutdown();
-
-  // Shutdown global servicemanager
-  if (nsComponentManagerImpl::gComponentManager) {
-    nsComponentManagerImpl::gComponentManager->FreeServices();
-  }
-
-  // Shutdown xpcom. This will release all loaders and cause others holding
-  // a refcount to the component manager to release it.
-  if (nsComponentManagerImpl::gComponentManager) {
-    rv = (nsComponentManagerImpl::gComponentManager)->Shutdown();
-    NS_ASSERTION(NS_SUCCEEDED(rv), "Component Manager shutdown failed.");
-  } else {
-    NS_WARNING("Component Manager was never created ...");
-  }
-
-  // Finally, release the component manager last because it unloads the
-  // libraries:
-  if (nsComponentManagerImpl::gComponentManager) {
-    nsrefcnt cnt;
-    NS_RELEASE2(nsComponentManagerImpl::gComponentManager, cnt);
-    NS_ASSERTION(cnt == 0, "Component Manager being held past XPCOM shutdown.");
-  }
-  nsComponentManagerImpl::gComponentManager = nullptr;
-  nsCategoryManager::Destroy();
-
-  return NS_OK;
-}

deleted file mode 100644
--- a/xpcom/libxpcomrt/XPCOMRTInit.h
+++ /dev/null
@@ -1,15 +0,0 @@
-/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
-/* vim:set ts=4 sw=4 sts=4 ci et: */
-/* 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 XPCOMRT_INIT_H__
-#define XPCOMRT_INIT_H__
-
-#include "nsError.h"
-
-nsresult NS_InitXPCOMRT();
-nsresult NS_ShutdownXPCOMRT();
-
-#endif // define XPCOMRT_INIT_H__

deleted file mode 100644
--- a/xpcom/libxpcomrt/XPCOMRTModule.inc
+++ /dev/null
@@ -1,8 +0,0 @@
-    COMPONENT(MEMORY, nsMemoryImpl::Create)
-    COMPONENT(DEBUG,  nsDebugImpl::Create)
-    COMPONENT(CATEGORYMANAGER, nsCategoryManager::Create)
-    COMPONENT(OBSERVERSERVICE, nsObserverService::Create)
-    COMPONENT(TIMER, nsTimerImplConstructor)
-    COMPONENT(THREADMANAGER, nsThreadManagerGetSingleton)
-    COMPONENT(THREADPOOL, nsThreadPoolConstructor)
-    COMPONENT(UUID_GENERATOR, nsUUIDGeneratorConstructor)

deleted file mode 100644
--- a/xpcom/libxpcomrt/XPCOMRTStubs.cpp
+++ /dev/null
@@ -1,65 +0,0 @@
-/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
-/* vim:set ts=4 sw=4 sts=4 ci et: */
-/* 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/. */
-
-#include "nsXULAppAPI.h"
-#include "mozilla/TimeStamp.h"
-
-
-GeckoProcessType
-XRE_GetProcessType()
-{
-  return GeckoProcessType_Default;
-}
-
-bool
-XRE_IsParentProcess()
-{
-  return XRE_GetProcessType() == GeckoProcessType_Default;
-}
-
-bool
-XRE_IsContentProcess()
-{
-  return XRE_GetProcessType() == GeckoProcessType_Content;
-}
-
-#define PRINT_CALLED fprintf(stderr, "!!! ERROR: function %s defined in file %s should not be called, needs to be correctly implemented.\n", __FUNCTION__, __FILE__)
-
-class nsAString;
-class nsCString;
-
-namespace base {
-  class Histogram;
-} // namespace base
-
-namespace mozilla {
-namespace Telemetry {
-
-#include "mozilla/TelemetryHistogramEnums.h"
-
-void Accumulate(ID id, uint32_t sample) {}
-void Accumulate(ID id, const nsCString& key, uint32_t sample) {}
-void Accumulate(const char* name, uint32_t sample) {}
-void AccumulateTimeDelta(ID id, TimeStamp start, TimeStamp end) {}
-
-base::Histogram* GetHistogramById(ID id)
-{
-  return nullptr;
-}
-
-base::Histogram* GetKeyedHistogramById(ID id, const nsAString&)
-{
-  return nullptr;
-}
-
-} // namespace Telemetry
-
-namespace detail {
-
-void log_print(const PRLogModuleInfo* aModule, LogLevel aLevel, const char* aFmt, ...) {}
-
-} // namespace detail
-} // namespace mozilla

deleted file mode 100644
--- a/xpcom/libxpcomrt/docs/index.rst
+++ /dev/null
@@ -1,40 +0,0 @@
-==========================
- XPCOM Standalone Library
-==========================
-
-What it is for
---------------
-The XPCOM standalone library, libxpcomrt, was created to support building the WebRTC
-standalone library. The libxpcomrt library contains only the parts of XPCOM that are required
-to run WebRTC; parts such as the cycle collector and the startup cache required only by Gecko
-are not included. A library containing a small subset of Necko was also
-created to support the WebRTC standalone library.
-
-The libxcomrt library was created specifically to support the WebRTC standalone library.
-It is not intended to be used as a general purpose library to add XPCOM functionality to
-an application. It is likely that some of the code contained in the libxpcomrt library
-has unresolved symbols that may be exposed if used for purposes other than being linked
-into the WebRTC standalone library.
-
-How to use it
--------------
-When compiling code utilizing libxpcomrt, both ``MOZILLA_INTERNAL_API`` and ``MOZILLA_XPCOMRT_API``
-must be defined in addition to whatever standard flags are used to compile Gecko.
-The library is initialized with ``NS_InitXPCOMRT()`` and shutdown with ``NS_ShutdownXPCOMRT()``.
-Both functions are declared in xpcom/libxpcomrt/XPCOMRTInit.h.
-Only a small number of services which are required for the WebRTC
-standalone library to function are included with libxpcomrt. The dynamic loading of services is not
-supported. Including a service through ``NSMODULE_DEFN`` and static linking is also not supported.
-The only way to add a service to libxpcomrt is to explicitly start the service during
-``nsComponentManagerImpl::Init`` in xpcom/components/nsComponentManager.cpp.
-The best method to determine what parts of XPCOM are included in libxpcomrt is to examine the
-xpcom/libxpcomrt/moz.build file. It contains all of the XPCOM source files used to build libxpcomrt.
-A few of the services that are included are:
-
-* UUID Generator
-* DNS Service
-* Socket Transport Service
-* IDN Service
-
-All dependencies on ipc/chromium have been removed.
-IO and preference services are not included making this library of limited utility.

deleted file mode 100644
--- a/xpcom/libxpcomrt/moz.build
+++ /dev/null
@@ -1,142 +0,0 @@
-# -*- Mode: python; c-basic-offset: 4; 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/.
-
-if CONFIG['OS_TARGET'] != 'WINNT' and CONFIG['MOZ_WIDGET_TOOLKIT'] != 'gonk':
-    Library('xpcomrt')
-
-src_list = [
-    'XPCOMRTInit.cpp',
-    'XPCOMRTStubs.cpp',
-]
-
-xpcom_base_src = [
-    'nsDebugImpl.cpp',
-    'nsMemoryImpl.cpp',
-    'nsUUIDGenerator.cpp',
-]
-src_list += [
-    '/xpcom/base/%s' % s for s in xpcom_base_src
-]
-
-xpcom_build_src = [
-    'FileLocation.cpp',
-    'Services.cpp',
-]
-src_list += [
-    '/xpcom/build/%s' % s for s in xpcom_build_src
-]
-
-xpcom_components_src = [
-    'nsCategoryManager.cpp',
-    'nsComponentManager.cpp',
-]
-src_list += [
-    '/xpcom/components/%s' % s for s in xpcom_components_src
-]
-
-xpcom_ds_src = [
-    'nsObserverList.cpp',
-    'nsObserverService.cpp',
-    'nsStringEnumerator.cpp',
-    'nsSupportsPrimitives.cpp',
-]
-
-src_list += [
-    '/xpcom/ds/%s' % s for s in xpcom_ds_src
-]
-
-xpcom_glue_src = [
-    'BlockingResourceBase.cpp',
-    'nsArrayEnumerator.cpp',
-    'nsClassInfoImpl.cpp',
-    'nsCOMArray.cpp',
-    'nsCOMPtr.cpp',
-    'nsCRTGlue.cpp',
-    'nsComponentManagerUtils.cpp',
-    'nsEnumeratorUtils.cpp',
-    'GenericFactory.cpp',
-    'nsID.cpp',
-    'nsISupportsImpl.cpp',
-    'nsMemory.cpp',
-    'nsQuickSort.cpp',
-    'nsTArray.cpp',
-    'nsTObserverArray.cpp',
-    'nsThreadUtils.cpp',
-    'nsWeakReference.cpp',
-    'PLDHashTable.cpp',
-]
-src_list += [
-    '/xpcom/glue/%s' % s for s in xpcom_glue_src
-]
-
-xpcom_io_src = [
-    'nsNativeCharsetUtils.cpp',
-]
-src_list += [
-    '/xpcom/io/%s' % s for s in xpcom_io_src
-]
-
-xpcom_string_src = [
-    'nsDependentSubstring.cpp',
-    'nsPromiseFlatString.cpp',
-    'nsReadableUtils.cpp',
-    'nsString.cpp',
-    'nsStringComparator.cpp',
-    'nsStringObsolete.cpp',
-    'nsSubstring.cpp',
-    'nsSubstringTuple.cpp',
-]
-if CONFIG['INTEL_ARCHITECTURE']:
-    xpcom_string_src += ['nsUTF8UtilsSSE2.cpp']
-src_list += [
-    '/xpcom/string/%s' % s for s in xpcom_string_src
-]
-
-xpcom_threads_src = [
-    'LazyIdleThread.cpp',
-    'nsEnvironment.cpp',
-    'nsEventQueue.cpp',
-    'nsMemoryPressure.cpp',
-    'nsProcessCommon.cpp',
-    'nsThread.cpp',
-    'nsThreadManager.cpp',
-    'nsThreadPool.cpp',
-    'nsTimerImpl.cpp',
-    'TimerThread.cpp',
-]
-src_list += [
-    '/xpcom/threads/%s' % s for s in xpcom_threads_src
-]
-
-
-SOURCES += sorted(src_list)
-
-if CONFIG['INTEL_ARCHITECTURE']:
-    sse_string_path = '/xpcom/string/nsUTF8UtilsSSE2.cpp'
-    SOURCES[sse_string_path].flags += CONFIG['SSE2_FLAGS']
-
-LOCAL_INCLUDES = [
-    '!..',
-    '../base',
-    '../build',
-    '../components',
-    '../ds',
-    '../glue',
-    '../threads',
-    '/netwerk/standalone/',
-    '/xpcom/reflect/xptinfo/',
-]
-
-DEFINES['MOZILLA_INTERNAL_API'] = True
-DEFINES['MOZILLA_XPCOMRT_API'] = True
-DEFINES['MOZILLA_EXTERNAL_LINKAGE'] = True
-
-include('/ipc/chromium/chromium-config.mozbuild')
-
-SPHINX_TREES['libxpcomrt'] = 'docs'
-
-if CONFIG['GNU_CXX']:
-    CXXFLAGS += ['-Wshadow']

--- a/xpcom/moz.build
+++ b/xpcom/moz.build
@@ -19,17 +19,16 @@ DIRS += [
     'ds',
     'io',
     'components',
     'threads',
     'reflect',
     'system',
     '../chrome',
     'build',
-    'libxpcomrt',
 ]
 
 if CONFIG['OS_ARCH'] == 'WINNT' and CONFIG['MOZ_DEBUG']:
     DIRS += ['windbgdlg']
 
 TEST_DIRS += [
     'tests',
 ]