--- a/browser/app/moz.build
+++ b/browser/app/moz.build
@@ -28,19 +28,16 @@ LOCAL_INCLUDES += [
     '/xpcom/base',
     '/xpcom/build',
 ]
 
 USE_LIBS += [
     'mozglue',
 ]
 
-if CONFIG['LIBFUZZER']:
-  USE_LIBS += [ 'fuzzer' ]
-
 if CONFIG['_MSC_VER']:
     # Always enter a Windows program through wmain, whether or not we're
     # a console application.
     WIN32_EXE_LDFLAGS += ['-ENTRY:wmainCRTStartup']
 
 if CONFIG['OS_ARCH'] == 'WINNT':
     RCINCLUDE = 'splash.rc'
     DEFINES['MOZ_PHOENIX'] = True

--- a/browser/app/nsBrowserApp.cpp
+++ b/browser/app/nsBrowserApp.cpp
@@ -124,52 +124,33 @@ XRE_TelemetryAccumulateType XRE_Telemetr
 XRE_StartupTimelineRecordType XRE_StartupTimelineRecord;
 XRE_mainType XRE_main;
 XRE_StopLateWriteChecksType XRE_StopLateWriteChecks;
 XRE_XPCShellMainType XRE_XPCShellMain;
 XRE_GetProcessTypeType XRE_GetProcessType;
 XRE_SetProcessTypeType XRE_SetProcessType;
 XRE_InitChildProcessType XRE_InitChildProcess;
 XRE_EnableSameExecutableForContentProcType XRE_EnableSameExecutableForContentProc;
-#ifdef LIBFUZZER
-XRE_LibFuzzerSetMainType XRE_LibFuzzerSetMain;
-XRE_LibFuzzerGetFuncsType XRE_LibFuzzerGetFuncs;
-#endif
 
 static const nsDynamicFunctionLoad kXULFuncs[] = {
     { "XRE_GetFileFromPath", (NSFuncPtr*) &XRE_GetFileFromPath },
     { "XRE_CreateAppData", (NSFuncPtr*) &XRE_CreateAppData },
     { "XRE_FreeAppData", (NSFuncPtr*) &XRE_FreeAppData },
     { "XRE_TelemetryAccumulate", (NSFuncPtr*) &XRE_TelemetryAccumulate },
     { "XRE_StartupTimelineRecord", (NSFuncPtr*) &XRE_StartupTimelineRecord },
     { "XRE_main", (NSFuncPtr*) &XRE_main },
     { "XRE_StopLateWriteChecks", (NSFuncPtr*) &XRE_StopLateWriteChecks },
     { "XRE_XPCShellMain", (NSFuncPtr*) &XRE_XPCShellMain },
     { "XRE_GetProcessType", (NSFuncPtr*) &XRE_GetProcessType },
     { "XRE_SetProcessType", (NSFuncPtr*) &XRE_SetProcessType },
     { "XRE_InitChildProcess", (NSFuncPtr*) &XRE_InitChildProcess },
     { "XRE_EnableSameExecutableForContentProc", (NSFuncPtr*) &XRE_EnableSameExecutableForContentProc },
-#ifdef LIBFUZZER
-    { "XRE_LibFuzzerSetMain", (NSFuncPtr*) &XRE_LibFuzzerSetMain },
-    { "XRE_LibFuzzerGetFuncs", (NSFuncPtr*) &XRE_LibFuzzerGetFuncs },
-#endif
     { nullptr, nullptr }
 };
 
-#ifdef LIBFUZZER
-int libfuzzer_main(int argc, char **argv);
-
-/* This wrapper is used by the libFuzzer main to call into libxul */
-
-void libFuzzerGetFuncs(const char* moduleName, LibFuzzerInitFunc* initFunc,
-                       LibFuzzerTestingFunc* testingFunc) {
-  return XRE_LibFuzzerGetFuncs(moduleName, initFunc, testingFunc);
-}
-#endif
-
 static int do_main(int argc, char* argv[], char* envp[], nsIFile *xreDirectory)
 {
   nsCOMPtr<nsIFile> appini;
   nsresult rv;
   uint32_t mainFlags = 0;
 
   // Allow firefox.exe to launch XULRunner apps via -app <application.ini>
   // Note that -app must be the *first* argument.
@@ -270,21 +251,16 @@ static int do_main(int argc, char* argv[
   if (!brokerServices) {
     Output("Couldn't initialize the broker services.\n");
     return 255;
   }
 #endif
   appData.sandboxBrokerServices = brokerServices;
 #endif
 
-#ifdef LIBFUZZER
-  if (getenv("LIBFUZZER"))
-    XRE_LibFuzzerSetMain(argc, argv, libfuzzer_main);
-#endif
-
   return XRE_main(argc, argv, &appData, mainFlags);
 }
 
 static bool
 FileExists(const char *path)
 {
 #ifdef XP_WIN
   wchar_t wideDir[MAX_PATH];

--- a/moz.build
+++ b/moz.build
@@ -52,17 +52,16 @@ if not CONFIG['JS_STANDALONE']:
 
 DIRS += [
     'config/external/fdlibm',
     'config/external/nspr',
     'config/external/zlib',
     'memory',
     'mfbt',
     'mozglue',
-    'tools/fuzzing',
 ]
 
 if not CONFIG['JS_STANDALONE']:
     DIRS += ['xpcom/xpidl']
 
 if CONFIG['USE_ICU']:
     DIRS += ['config/external/icu']
 

--- a/toolkit/moz.configure
+++ b/toolkit/moz.configure
@@ -759,20 +759,8 @@ def skia_includes(skia, skia_gpu):
         includes += [
             '/gfx/skia/skia/include/gpu',
             '/gfx/skia/skia/include/utils',
         ]
 
     return includes
 
 set_config('SKIA_INCLUDES', skia_includes)
-
-# Support various fuzzing options
-# ==============================================================
-option('--enable-libfuzzer', help='Enable libfuzzer support')
-
-@depends('--enable-libfuzzer')
-def enable_libfuzzer(value):
-    if value:
-        return True
-
-set_config('LIBFUZZER', enable_libfuzzer)
-set_define('LIBFUZZER', enable_libfuzzer)

--- a/toolkit/xre/nsAppRunner.cpp
+++ b/toolkit/xre/nsAppRunner.cpp
@@ -253,28 +253,16 @@ nsString gAbsoluteArgv0Path;
 // build backends.
 #include "buildid.h"
 #endif
 
 #ifdef MOZ_LINKER
 extern "C" MFBT_API bool IsSignalHandlingBroken();
 #endif
 
-#ifdef LIBFUZZER
-#include "LibFuzzerRunner.h"
-
-namespace mozilla {
-LibFuzzerRunner* libFuzzerRunner = 0;
-} // namespace mozilla
-
-extern "C" MOZ_EXPORT void XRE_LibFuzzerSetMain(int argc, char** argv, LibFuzzerMain main) {
-  mozilla::libFuzzerRunner->setParams(argc, argv, main);
-}
-#endif
-
 namespace mozilla {
 int (*RunGTest)() = 0;
 } // namespace mozilla
 
 using namespace mozilla;
 using mozilla::Unused;
 using mozilla::scache::StartupCache;
 using mozilla::dom::ContentParent;
@@ -3651,23 +3639,16 @@ XREMain::XRE_mainStartup(bool* aExitFlag
 
   // Open the display ourselves instead of using gtk_init, so that we can
   // close it without fear that one day gtk might clean up the display it
   // opens.
   if (!gtk_parse_args(&gArgc, &gArgv))
     return 1;
 #endif /* MOZ_WIDGET_GTK */
 
-#ifdef LIBFUZZER
-  if (PR_GetEnv("LIBFUZZER")) {
-    *aExitFlag = true;
-    return mozilla::libFuzzerRunner->Run();
-  }
-#endif
-
   if (PR_GetEnv("MOZ_RUN_GTEST")) {
     int result;
 #ifdef XP_WIN
     UseParentConsole();
 #endif
     // RunGTest will only be set if we're in xul-unit
     if (mozilla::RunGTest) {
       gIsGtest = true;

deleted file mode 100644
--- a/tools/fuzzing/libfuzzer/FuzzerCustomMain.cpp
+++ /dev/null
@@ -1,37 +0,0 @@
-/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
- * * 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 <cstdlib>
-
-#include "FuzzerInterface.h"
-#include "FuzzerInternal.h"
-#include "harness/LibFuzzerRegistry.h"
-
-/* This is a wrapper defined in browser/app/nsBrowserApp.cpp,
- * encapsulating the XRE_ equivalent defined in libxul */
-extern void libFuzzerGetFuncs(const char*, LibFuzzerInitFunc*,
-                                 LibFuzzerTestingFunc*);
-
-int libfuzzer_main(int argc, char **argv) {
-  LibFuzzerInitFunc initFunc = nullptr;
-  LibFuzzerTestingFunc testingFunc = nullptr;
-
-  libFuzzerGetFuncs(getenv("LIBFUZZER"), &initFunc, &testingFunc);
-
-  if (initFunc) {
-    int ret = initFunc(&argc, &argv);
-    if (ret) {
-      fprintf(stderr, "LibFuzzer: Error: Initialize callback failed\n");
-      return ret;
-    }
-  }
-
-  if (!testingFunc) {
-      fprintf(stderr, "LibFuzzer: Error: No testing callback found\n");
-      return 1;
-  }
-
-  return fuzzer::FuzzerDriver(&argc, &argv, testingFunc);
-}

deleted file mode 100644
--- a/tools/fuzzing/libfuzzer/Makefile.in
+++ /dev/null
@@ -1,12 +0,0 @@
-# This Source Code Form is subject to the terms of the Mozilla Public
-# License, v. 2.0. If a copy of the MPL was not distributed with this
-# file, You can obtain one at http://mozilla.org/MPL/2.0/.
-
-include $(topsrcdir)/config/rules.mk
-
-# According to the LLVM docs, LibFuzzer isn't supposed to be built with any
-# sanitizer flags and in fact, building it with ASan coverage currently causes
-# Clang 3.9+ to crash, so we filter out all sanitizer-related flags here.
-CXXFLAGS := $(filter-out -fsanitize%,$(CXXFLAGS))
-CFLAGS := $(filter-out -fsanitize%,$(CFLAGS))
-LDFLAGS := $(filter-out -fsanitize%,$(LDFLAGS))

deleted file mode 100755
--- a/tools/fuzzing/libfuzzer/clone_libfuzzer.sh
+++ /dev/null
@@ -1,7 +0,0 @@
-#!/bin/sh
-
-mkdir tmp/
-git clone --no-checkout --depth 1 https://chromium.googlesource.com/chromium/llvm-project/llvm/lib/Fuzzer tmp/
-mv tmp/.git .
-rm -Rf tmp
-git reset --hard HEAD

deleted file mode 100644
--- a/tools/fuzzing/libfuzzer/harness/LibFuzzerRegistry.cpp
+++ /dev/null
@@ -1,32 +0,0 @@
-/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
- * * 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 "LibFuzzerRegistry.h"
-
-extern "C" {
-    void MOZ_EXPORT XRE_LibFuzzerGetFuncs(const char* moduleName, LibFuzzerInitFunc* initFunc, LibFuzzerTestingFunc* testingFunc) {
-        std::string moduleNameStr(moduleName);
-        mozilla::LibFuzzerFunctions funcs = mozilla::LibFuzzerRegistry::getInstance().getModuleFunctions(moduleNameStr);
-        *initFunc = funcs.first;
-        *testingFunc = funcs.second;
-    }
-}
-
-namespace mozilla {
-
-LibFuzzerRegistry& LibFuzzerRegistry::getInstance() {
-    static LibFuzzerRegistry instance;
-    return instance;
-}
-
-void LibFuzzerRegistry::registerModule(std::string moduleName, LibFuzzerInitFunc initFunc, LibFuzzerTestingFunc testingFunc) {
-    moduleMap.insert(std::pair<std::string, LibFuzzerFunctions>(moduleName,LibFuzzerFunctions(initFunc, testingFunc)));
-}
-
-LibFuzzerFunctions LibFuzzerRegistry::getModuleFunctions(std::string& moduleName) {
-    return moduleMap[moduleName];
-}
-
-} // namespace mozilla

deleted file mode 100644
--- a/tools/fuzzing/libfuzzer/harness/LibFuzzerRegistry.h
+++ /dev/null
@@ -1,41 +0,0 @@
-/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
- * * 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 _LibFuzzerRegistry_h__
-#define _LibFuzzerRegistry_h__
-
-#include <cstdint>
-#include <map>
-#include <string>
-#include <utility>
-
-#include "mozilla/Attributes.h"
-
-typedef int(*LibFuzzerMain)(int, char**);
-typedef int(*LibFuzzerInitFunc)(int*, char***);
-typedef int(*LibFuzzerTestingFunc)(const uint8_t*, size_t);
-
-namespace mozilla {
-
-typedef std::pair<LibFuzzerInitFunc, LibFuzzerTestingFunc> LibFuzzerFunctions;
-
-class LibFuzzerRegistry {
-    public:
-        MOZ_EXPORT static LibFuzzerRegistry& getInstance();
-        MOZ_EXPORT void registerModule(std::string moduleName, LibFuzzerInitFunc initFunc, LibFuzzerTestingFunc testingFunc);
-        MOZ_EXPORT LibFuzzerFunctions getModuleFunctions(std::string& moduleName);
-
-        LibFuzzerRegistry(LibFuzzerRegistry const&) = delete;
-        void operator=(LibFuzzerRegistry const&) = delete;
-
-    private:
-        LibFuzzerRegistry() {};
-        std::map<std::string, LibFuzzerFunctions> moduleMap;
-};
-
-} // namespace mozilla
-
-
-#endif // _LibFuzzerRegistry_h__

deleted file mode 100644
--- a/tools/fuzzing/libfuzzer/harness/LibFuzzerRunner.cpp
+++ /dev/null
@@ -1,38 +0,0 @@
-/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
- * * 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 "LibFuzzerRunner.h"
-#include "mozilla/Attributes.h"
-#include "prenv.h"
-
-#include "LibFuzzerTestHarness.h"
-
-namespace mozilla {
-
-// We use a static var 'libFuzzerRunner' defined in nsAppRunner.cpp.
-// libFuzzerRunner is initialized to nullptr but if LibFuzzer (this file)
-// is linked in then libFuzzerRunner will be set here indicating that
-// we want to call into LibFuzzer's main.
-class _InitLibFuzzer {
-public:
-  _InitLibFuzzer() {
-    libFuzzerRunner = new LibFuzzerRunner();
-  }
-} InitLibFuzzer;
-
-int LibFuzzerRunner::Run() {
-  ScopedXPCOM xpcom("LibFuzzer");
-  return mFuzzerMain(mArgc, mArgv);
-}
-
-typedef int(*LibFuzzerMain)(int, char**);
-
-void LibFuzzerRunner::setParams(int argc, char** argv, LibFuzzerMain main) {
-  mArgc = argc;
-  mArgv = argv;
-  mFuzzerMain = main;
-}
-
-} // namespace mozilla

deleted file mode 100644
--- a/tools/fuzzing/libfuzzer/harness/LibFuzzerRunner.h
+++ /dev/null
@@ -1,23 +0,0 @@
-/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
- * * 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/. */
-
-namespace mozilla {
-
-typedef int(*LibFuzzerMain)(int, char**);
-
-class LibFuzzerRunner {
-public:
-  int Run();
-  void setParams(int argc, char** argv, LibFuzzerMain main);
-
-private:
-  int mArgc;
-  char** mArgv;
-  LibFuzzerMain mFuzzerMain;
-};
-
-extern LibFuzzerRunner* libFuzzerRunner;
-
-} // namespace mozilla

deleted file mode 100644
--- a/tools/fuzzing/libfuzzer/harness/LibFuzzerTestHarness.h
+++ /dev/null
@@ -1,312 +0,0 @@
-/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
-/* 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/. */
-
-/*
- * Test harness for XPCOM objects, providing a scoped XPCOM initializer,
- * nsCOMPtr, nsRefPtr, do_CreateInstance, do_GetService, ns(Auto|C|)String,
- * and stdio.h/stdlib.h.
- */
-
-#ifndef LibFuzzerTestHarness_h__
-#define LibFuzzerTestHarness_h__
-
-#include "mozilla/ArrayUtils.h"
-
-#include "prenv.h"
-#include "nsComponentManagerUtils.h"
-#include "nsServiceManagerUtils.h"
-#include "nsCOMPtr.h"
-#include "nsAutoPtr.h"
-#include "nsStringGlue.h"
-#include "nsAppDirectoryServiceDefs.h"
-#include "nsDirectoryServiceDefs.h"
-#include "nsDirectoryServiceUtils.h"
-#include "nsIDirectoryService.h"
-#include "nsIFile.h"
-#include "nsIProperties.h"
-#include "nsIObserverService.h"
-#include "nsXULAppAPI.h"
-#include <stdio.h>
-#include <stdlib.h>
-#include <stdarg.h>
-
-namespace {
-
-static uint32_t gFailCount = 0;
-
-/**
- * Prints the given failure message and arguments using printf, prepending
- * "TEST-UNEXPECTED-FAIL " for the benefit of the test harness and
- * appending "\n" to eliminate having to type it at each call site.
- */
-void fail(const char* msg, ...)
-{
-  va_list ap;
-
-  printf("TEST-UNEXPECTED-FAIL | ");
-
-  va_start(ap, msg);
-  vprintf(msg, ap);
-  va_end(ap);
-
-  putchar('\n');
-  ++gFailCount;
-}
-
-/**
- * Prints the given success message and arguments using printf, prepending
- * "TEST-PASS " for the benefit of the test harness and
- * appending "\n" to eliminate having to type it at each call site.
- */
-void passed(const char* msg, ...)
-{
-  va_list ap;
-
-  printf("TEST-PASS | ");
-
-  va_start(ap, msg);
-  vprintf(msg, ap);
-  va_end(ap);
-
-  putchar('\n');
-}
-
-//-----------------------------------------------------------------------------
-
-class ScopedLogging
-{
-public:
-    ScopedLogging()
-    {
-        NS_LogInit();
-    }
-
-    ~ScopedLogging()
-    {
-        NS_LogTerm();
-    }
-};
-
-static class ScopedXPCOM : public nsIDirectoryServiceProvider2
-{
-  public:
-    NS_DECL_ISUPPORTS
-
-    explicit ScopedXPCOM(const char* testName,
-                         nsIDirectoryServiceProvider *dirSvcProvider = nullptr)
-    : mDirSvcProvider(dirSvcProvider)
-    {
-      mTestName = testName;
-      printf("Running %s tests...\n", mTestName);
-
-      nsresult rv = NS_InitXPCOM2(&mServMgr, nullptr, this);
-      if (NS_FAILED(rv))
-      {
-        fail("NS_InitXPCOM2 returned failure code 0x%x", rv);
-        mServMgr = nullptr;
-        return;
-      }
-    }
-
-    ~ScopedXPCOM()
-    {
-      // If we created a profile directory, we need to remove it.
-      if (mProfD) {
-        nsCOMPtr<nsIObserverService> os =
-          do_GetService(NS_OBSERVERSERVICE_CONTRACTID);
-        MOZ_ASSERT(os);
-        if (os) {
-          MOZ_ALWAYS_SUCCEEDS(os->NotifyObservers(nullptr, "profile-change-net-teardown", nullptr));
-          MOZ_ALWAYS_SUCCEEDS(os->NotifyObservers(nullptr, "profile-change-teardown", nullptr));
-          MOZ_ALWAYS_SUCCEEDS(os->NotifyObservers(nullptr, "profile-before-change", nullptr));
-          MOZ_ALWAYS_SUCCEEDS(os->NotifyObservers(nullptr, "profile-before-change-qm", nullptr));
-          MOZ_ALWAYS_SUCCEEDS(os->NotifyObservers(nullptr, "profile-before-change-telemetry", nullptr));
-        }
-
-        if (NS_FAILED(mProfD->Remove(true))) {
-          NS_WARNING("Problem removing profile directory");
-        }
-
-        mProfD = nullptr;
-      }
-
-      if (mServMgr)
-      {
-        NS_RELEASE(mServMgr);
-        nsresult rv = NS_ShutdownXPCOM(nullptr);
-        if (NS_FAILED(rv))
-        {
-          fail("XPCOM shutdown failed with code 0x%x", rv);
-          exit(1);
-        }
-      }
-
-      printf("Finished running %s tests.\n", mTestName);
-    }
-
-    bool failed()
-    {
-      return mServMgr == nullptr;
-    }
-
-    already_AddRefed<nsIFile> GetProfileDirectory()
-    {
-      if (mProfD) {
-        nsCOMPtr<nsIFile> copy = mProfD;
-        return copy.forget();
-      }
-
-      // Create a unique temporary folder to use for this test.
-      // Note that runcppunittests.py will run tests with a temp
-      // directory as the cwd, so just put something under that.
-      nsCOMPtr<nsIFile> profD;
-      nsresult rv = NS_GetSpecialDirectory(NS_OS_CURRENT_PROCESS_DIR,
-                                           getter_AddRefs(profD));
-      NS_ENSURE_SUCCESS(rv, nullptr);
-
-      rv = profD->Append(NS_LITERAL_STRING("cpp-unit-profd"));
-      NS_ENSURE_SUCCESS(rv, nullptr);
-
-      rv = profD->CreateUnique(nsIFile::DIRECTORY_TYPE, 0755);
-      NS_ENSURE_SUCCESS(rv, nullptr);
-
-      mProfD = profD;
-      return profD.forget();
-    }
-
-    already_AddRefed<nsIFile> GetGREDirectory()
-    {
-      if (mGRED) {
-        nsCOMPtr<nsIFile> copy = mGRED;
-        return copy.forget();
-      }
-
-      char* env = PR_GetEnv("MOZ_XRE_DIR");
-      nsCOMPtr<nsIFile> greD;
-      if (env) {
-        NS_NewLocalFile(NS_ConvertUTF8toUTF16(env), false,
-                        getter_AddRefs(greD));
-      }
-
-      mGRED = greD;
-      return greD.forget();
-    }
-
-    already_AddRefed<nsIFile> GetGREBinDirectory()
-    {
-      if (mGREBinD) {
-        nsCOMPtr<nsIFile> copy = mGREBinD;
-        return copy.forget();
-      }
-
-      nsCOMPtr<nsIFile> greD = GetGREDirectory();
-      if (!greD) {
-        return greD.forget();
-      }
-      greD->Clone(getter_AddRefs(mGREBinD));
-
-#ifdef XP_MACOSX
-      nsAutoCString leafName;
-      mGREBinD->GetNativeLeafName(leafName);
-      if (leafName.Equals("Resources")) {
-        mGREBinD->SetNativeLeafName(NS_LITERAL_CSTRING("MacOS"));
-      }
-#endif
-
-      nsCOMPtr<nsIFile> copy = mGREBinD;
-      return copy.forget();
-    }
-
-    ////////////////////////////////////////////////////////////////////////////
-    //// nsIDirectoryServiceProvider
-
-    NS_IMETHODIMP GetFile(const char *aProperty, bool *_persistent,
-                          nsIFile **_result) override
-    {
-      // If we were supplied a directory service provider, ask it first.
-      if (mDirSvcProvider &&
-          NS_SUCCEEDED(mDirSvcProvider->GetFile(aProperty, _persistent,
-                                                _result))) {
-        return NS_OK;
-      }
-
-      // Otherwise, the test harness provides some directories automatically.
-      if (0 == strcmp(aProperty, NS_APP_USER_PROFILE_50_DIR) ||
-          0 == strcmp(aProperty, NS_APP_USER_PROFILE_LOCAL_50_DIR) ||
-          0 == strcmp(aProperty, NS_APP_PROFILE_LOCAL_DIR_STARTUP)) {
-        nsCOMPtr<nsIFile> profD = GetProfileDirectory();
-        NS_ENSURE_TRUE(profD, NS_ERROR_FAILURE);
-
-        nsCOMPtr<nsIFile> clone;
-        nsresult rv = profD->Clone(getter_AddRefs(clone));
-        NS_ENSURE_SUCCESS(rv, rv);
-
-        *_persistent = true;
-        clone.forget(_result);
-        return NS_OK;
-      } else if (0 == strcmp(aProperty, NS_GRE_DIR)) {
-        nsCOMPtr<nsIFile> greD = GetGREDirectory();
-        NS_ENSURE_TRUE(greD, NS_ERROR_FAILURE);
-
-        *_persistent = true;
-        greD.forget(_result);
-        return NS_OK;
-      } else if (0 == strcmp(aProperty, NS_GRE_BIN_DIR)) {
-        nsCOMPtr<nsIFile> greBinD = GetGREBinDirectory();
-        NS_ENSURE_TRUE(greBinD, NS_ERROR_FAILURE);
-
-        *_persistent = true;
-        greBinD.forget(_result);
-        return NS_OK;
-      }
-
-      return NS_ERROR_FAILURE;
-    }
-
-    ////////////////////////////////////////////////////////////////////////////
-    //// nsIDirectoryServiceProvider2
-
-    NS_IMETHODIMP GetFiles(const char *aProperty, nsISimpleEnumerator **_enum) override
-    {
-      // If we were supplied a directory service provider, ask it first.
-      nsCOMPtr<nsIDirectoryServiceProvider2> provider =
-        do_QueryInterface(mDirSvcProvider);
-      if (provider && NS_SUCCEEDED(provider->GetFiles(aProperty, _enum))) {
-        return NS_OK;
-      }
-
-     return NS_ERROR_FAILURE;
-   }
-
-  private:
-    const char* mTestName;
-    nsIServiceManager* mServMgr;
-    nsCOMPtr<nsIDirectoryServiceProvider> mDirSvcProvider;
-    nsCOMPtr<nsIFile> mProfD;
-    nsCOMPtr<nsIFile> mGRED;
-    nsCOMPtr<nsIFile> mGREBinD;
-};
-
-NS_IMPL_QUERY_INTERFACE(
-  ScopedXPCOM,
-  nsIDirectoryServiceProvider,
-  nsIDirectoryServiceProvider2
-)
-
-NS_IMETHODIMP_(MozExternalRefCountType)
-ScopedXPCOM::AddRef()
-{
-  return 2;
-}
-
-NS_IMETHODIMP_(MozExternalRefCountType)
-ScopedXPCOM::Release()
-{
-  return 1;
-}
-
-} // namespace
-
-#endif  // LibFuzzerTestHarness_h__

deleted file mode 100644
--- a/tools/fuzzing/libfuzzer/harness/moz.build
+++ /dev/null
@@ -1,19 +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/.
-
-Library('fuzzer-runner')
-
-SOURCES += [
-    'LibFuzzerRegistry.cpp',
-    'LibFuzzerRunner.cpp',
-]
-
-EXPORTS += [
-    'LibFuzzerRegistry.h',
-    'LibFuzzerRunner.h',
-]
-
-FINAL_LIBRARY = "xul"

deleted file mode 100644
--- a/tools/fuzzing/libfuzzer/moz.build
+++ /dev/null
@@ -1,26 +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/.
-
-Library('fuzzer')
-
-DIRS += [
-  'harness',
-]
-
-SOURCES += [
-    'FuzzerCrossOver.cpp',
-    'FuzzerCustomMain.cpp',
-    'FuzzerDriver.cpp',
-    'FuzzerExtFunctionsDlsym.cpp',
-    'FuzzerExtFunctionsWeak.cpp',
-    'FuzzerIO.cpp',
-    'FuzzerLoop.cpp',
-    'FuzzerMutate.cpp',
-    'FuzzerSHA1.cpp',
-    'FuzzerTracePC.cpp',
-    'FuzzerTraceState.cpp',
-    'FuzzerUtil.cpp',
-]

deleted file mode 100644
--- a/tools/fuzzing/moz.build
+++ /dev/null
@@ -1,10 +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['LIBFUZZER']:
-  DIRS += [
-    'libfuzzer',
-  ]

--- a/xpcom/build/nsXULAppAPI.h
+++ b/xpcom/build/nsXULAppAPI.h
@@ -515,21 +515,9 @@ XRE_API(int,
         XRE_XPCShellMain, (int argc, char** argv, char** envp,
                            const XREShellData* aShellData))
 
 #if MOZ_WIDGET_GTK == 2
 XRE_API(void,
         XRE_GlibInit, ())
 #endif
 
-
-#ifdef LIBFUZZER
-#include "LibFuzzerRegistry.h"
-
-XRE_API(void,
-        XRE_LibFuzzerSetMain, (int, char**, LibFuzzerMain))
-
-XRE_API(void,
-        XRE_LibFuzzerGetFuncs, (const char*, LibFuzzerInitFunc*,
-                                LibFuzzerTestingFunc*))
-#endif // LIBFUZZER
-
 #endif // _nsXULAppAPI_h__