--- a/dom/ipc/ContentParent.cpp
+++ b/dom/ipc/ContentParent.cpp
@@ -238,23 +238,16 @@ using namespace mozilla::system;
 #endif
 
 #include "Crypto.h"
 
 #ifdef MOZ_WEBSPEECH
 #include "mozilla/dom/SpeechSynthesisParent.h"
 #endif
 
-#ifdef ENABLE_TESTS
-#include "BackgroundChildImpl.h"
-#include "mozilla/ipc/PBackgroundChild.h"
-#include "nsIIPCBackgroundChildCreateCallback.h"
-#endif
-
-
 #if defined(MOZ_CONTENT_SANDBOX) && defined(XP_LINUX)
 #include "mozilla/SandboxInfo.h"
 #include "mozilla/SandboxBroker.h"
 #include "mozilla/SandboxBrokerPolicyFactory.h"
 #endif
 
 #ifdef MOZ_TOOLKIT_SEARCH
 #include "nsIBrowserSearchService.h"
@@ -302,140 +295,16 @@ using namespace mozilla::gmp;
 using namespace mozilla::hal;
 using namespace mozilla::ipc;
 using namespace mozilla::layers;
 using namespace mozilla::net;
 using namespace mozilla::jsipc;
 using namespace mozilla::psm;
 using namespace mozilla::widget;
 
-#ifdef ENABLE_TESTS
-
-class BackgroundTester final : public nsIIPCBackgroundChildCreateCallback,
-                               public nsIObserver
-{
-  static uint32_t sCallbackCount;
-
-private:
-  ~BackgroundTester()
-  { }
-
-  virtual void
-  ActorCreated(PBackgroundChild* aActor) override
-  {
-    MOZ_RELEASE_ASSERT(aActor,
-                       "Failed to create a PBackgroundChild actor!");
-
-    NS_NAMED_LITERAL_CSTRING(testStr, "0123456789");
-
-    PBackgroundTestChild* testActor =
-      aActor->SendPBackgroundTestConstructor(testStr);
-    MOZ_RELEASE_ASSERT(testActor);
-
-    if (!sCallbackCount) {
-      PBackgroundChild* existingBackgroundChild =
-        BackgroundChild::GetForCurrentThread();
-
-      MOZ_RELEASE_ASSERT(existingBackgroundChild);
-      MOZ_RELEASE_ASSERT(existingBackgroundChild == aActor);
-
-      bool ok =
-        existingBackgroundChild->
-          SendPBackgroundTestConstructor(testStr);
-      MOZ_RELEASE_ASSERT(ok);
-
-      // Callback 3.
-      ok = BackgroundChild::GetOrCreateForCurrentThread(this);
-      MOZ_RELEASE_ASSERT(ok);
-    }
-
-    sCallbackCount++;
-  }
-
-  virtual void
-  ActorFailed() override
-  {
-    MOZ_CRASH("Failed to create a PBackgroundChild actor!");
-  }
-
-  NS_IMETHOD
-  Observe(nsISupports* aSubject, const char* aTopic, const char16_t* aData)
-      override
-  {
-    nsCOMPtr<nsIObserverService> observerService =
-      mozilla::services::GetObserverService();
-    MOZ_RELEASE_ASSERT(observerService);
-
-    nsresult rv = observerService->RemoveObserver(this, aTopic);
-    MOZ_RELEASE_ASSERT(NS_SUCCEEDED(rv));
-
-    if (!strcmp(aTopic, "profile-after-change")) {
-      if (mozilla::Preferences::GetBool("pbackground.testing", false)) {
-        rv = observerService->AddObserver(this, "xpcom-shutdown", false);
-        MOZ_RELEASE_ASSERT(NS_SUCCEEDED(rv));
-
-        // Callback 1.
-        bool ok = BackgroundChild::GetOrCreateForCurrentThread(this);
-        MOZ_RELEASE_ASSERT(ok);
-
-        BackgroundChildImpl::ThreadLocal* threadLocal =
-          BackgroundChildImpl::GetThreadLocalForCurrentThread();
-        MOZ_RELEASE_ASSERT(threadLocal);
-
-        // Callback 2.
-        ok = BackgroundChild::GetOrCreateForCurrentThread(this);
-        MOZ_RELEASE_ASSERT(ok);
-      }
-
-      return NS_OK;
-    }
-
-    if (!strcmp(aTopic, "xpcom-shutdown")) {
-      MOZ_RELEASE_ASSERT(sCallbackCount == 3);
-
-      return NS_OK;
-    }
-
-    MOZ_CRASH("Unknown observer topic!");
-  }
-
-public:
-  NS_DECL_ISUPPORTS
-};
-
-uint32_t BackgroundTester::sCallbackCount = 0;
-
-NS_IMPL_ISUPPORTS(BackgroundTester, nsIIPCBackgroundChildCreateCallback,
-                  nsIObserver)
-
-#endif // ENABLE_TESTS
-
-void
-MaybeTestPBackground()
-{
-#ifdef ENABLE_TESTS
-  // This test relies on running the event loop and XPCShell does not always
-  // do so. Bail out here if we detect that we're running in XPCShell.
-  if (PR_GetEnv("XPCSHELL_TEST_PROFILE_DIR")) {
-    return;
-  }
-
-  // This is called too early at startup to test preferences directly. We have
-  // to install an observer to be notified when preferences are available.
-  nsCOMPtr<nsIObserverService> observerService =
-    mozilla::services::GetObserverService();
-  MOZ_RELEASE_ASSERT(observerService);
-
-  nsCOMPtr<nsIObserver> observer = new BackgroundTester();
-  nsresult rv = observerService->AddObserver(observer, "profile-after-change",
-                                             false);
-  MOZ_RELEASE_ASSERT(NS_SUCCEEDED(rv));
-#endif
-}
-
 // XXX Workaround for bug 986973 to maintain the existing broken semantics
 template<>
 struct nsIConsoleService::COMTypeInfo<nsConsoleService, void> {
   static const nsIID kIID;
 };
 const nsIID nsIConsoleService::COMTypeInfo<nsConsoleService, void>::kIID = NS_ICONSOLESERVICE_IID;
 
 namespace mozilla {
@@ -859,20 +728,16 @@ ContentParent::StartUp()
 
   BlobParent::Startup(BlobParent::FriendKey());
 
   BackgroundChild::Startup();
 
   // Try to preallocate a process that we can transform into an app later.
   PreallocatedProcessManager::AllocateAfterDelay();
 
-  // Test the PBackground infrastructure on ENABLE_TESTS builds when a special
-  // testing preference is set.
-  MaybeTestPBackground();
-
   sDisableUnsafeCPOWWarnings = PR_GetEnv("DISABLE_UNSAFE_CPOW_WARNINGS");
 
 #if defined(XP_LINUX) && defined(MOZ_CONTENT_SANDBOX)
   sSandboxBrokerPolicyFactory = MakeUnique<SandboxBrokerPolicyFactory>();
 #endif
 }
 
 /*static*/ void
@@ -3690,23 +3555,21 @@ ContentParent::DeallocPRemoteSpellcheckE
 {
   delete parent;
   return true;
 }
 
 /* static */ void
 ContentParent::ForceKillTimerCallback(nsITimer* aTimer, void* aClosure)
 {
-#ifdef ENABLE_TESTS
   // We don't want to time out the content process during XPCShell tests. This
   // is the easiest way to ensure that.
   if (PR_GetEnv("XPCSHELL_TEST_PROFILE_DIR")) {
     return;
   }
-#endif
 
   auto self = static_cast<ContentParent*>(aClosure);
   self->KillHard("ShutDownKill");
 }
 
 void
 ContentParent::KillHard(const char* aReason)
 {

--- a/dom/workers/RuntimeService.cpp
+++ b/dom/workers/RuntimeService.cpp
@@ -62,22 +62,16 @@
 
 #include "Principal.h"
 #include "SharedWorker.h"
 #include "WorkerDebuggerManager.h"
 #include "WorkerPrivate.h"
 #include "WorkerRunnable.h"
 #include "WorkerThread.h"
 
-#ifdef ENABLE_TESTS
-#include "BackgroundChildImpl.h"
-#include "mozilla/ipc/PBackgroundChild.h"
-#include "prrng.h"
-#endif
-
 using namespace mozilla;
 using namespace mozilla::dom;
 using namespace mozilla::ipc;
 
 USING_WORKERS_NAMESPACE
 
 using mozilla::MutexAutoLock;
 using mozilla::MutexAutoUnlock;
@@ -157,20 +151,16 @@ const JS::ContextOptions kRequiredContex
 uint32_t gMaxWorkersPerDomain = MAX_WORKERS_PER_DOMAIN;
 
 // Does not hold an owning reference.
 RuntimeService* gRuntimeService = nullptr;
 
 // Only true during the call to Init.
 bool gRuntimeServiceDuringInit = false;
 
-#ifdef ENABLE_TESTS
-bool gTestPBackground = false;
-#endif // ENABLE_TESTS
-
 class LiteralRebindingCString : public nsDependentCString
 {
 public:
   template<int N>
   void RebindLiteral(const char (&aStr)[N])
   {
     Rebind(aStr, N-1);
   }
@@ -981,68 +971,16 @@ public:
       CycleCollectedJSRuntime::AfterProcessTask(aRecursionDepth);
     }
   }
 
 private:
   WorkerPrivate* mWorkerPrivate;
 };
 
-#ifdef ENABLE_TESTS
-
-class TestPBackgroundCreateCallback final :
-  public nsIIPCBackgroundChildCreateCallback
-{
-public:
-  NS_DECL_ISUPPORTS
-
-  virtual void
-  ActorCreated(PBackgroundChild* aActor) override
-  {
-    MOZ_RELEASE_ASSERT(aActor);
-  }
-
-  virtual void
-  ActorFailed() override
-  {
-    MOZ_CRASH("TestPBackground() should not fail "
-              "GetOrCreateForCurrentThread()");
-  }
-
-private:
-  ~TestPBackgroundCreateCallback()
-  { }
-};
-
-NS_IMPL_ISUPPORTS(TestPBackgroundCreateCallback,
-                  nsIIPCBackgroundChildCreateCallback);
-
-void
-TestPBackground()
-{
-  using namespace mozilla::ipc;
-
-  if (gTestPBackground) {
-    // Randomize value to validate workers are not cross-posting messages.
-    uint32_t testValue;
-    size_t randomSize = PR_GetRandomNoise(&testValue, sizeof(testValue));
-    MOZ_RELEASE_ASSERT(randomSize == sizeof(testValue));
-    nsCString testStr;
-    testStr.AppendInt(testValue);
-    testStr.AppendInt(reinterpret_cast<int64_t>(PR_GetCurrentThread()));
-    PBackgroundChild* existingBackgroundChild =
-      BackgroundChild::GetForCurrentThread();
-    MOZ_RELEASE_ASSERT(existingBackgroundChild);
-    bool ok = existingBackgroundChild->SendPBackgroundTestConstructor(testStr);
-    MOZ_RELEASE_ASSERT(ok);
-  }
-}
-
-#endif // ENABLE_TESTS
-
 class WorkerBackgroundChildCallback final :
   public nsIIPCBackgroundChildCreateCallback
 {
   bool* mDone;
 
 public:
   explicit WorkerBackgroundChildCallback(bool* aDone)
   : mDone(aDone)
@@ -1416,20 +1354,16 @@ RuntimeService::GetOrCreateService()
     // The observer service now owns us until shutdown.
     gRuntimeService = new RuntimeService();
     if (NS_FAILED(gRuntimeService->Init())) {
       NS_WARNING("Failed to initialize!");
       gRuntimeService->Cleanup();
       gRuntimeService = nullptr;
       return nullptr;
     }
-
-#ifdef ENABLE_TESTS
-    gTestPBackground = mozilla::Preferences::GetBool("pbackground.testing", false);
-#endif // ENABLE_TESTS
   }
 
   return gRuntimeService;
 }
 
 // static
 RuntimeService*
 RuntimeService::GetService()
@@ -2698,20 +2632,16 @@ WorkerThreadPrimaryRunnable::Run()
   nsresult rv = SynchronouslyCreatePBackground();
   if (NS_WARN_IF(NS_FAILED(rv))) {
     // XXX need to fire an error at parent.
     return rv;
   }
 
   mWorkerPrivate->SetThread(mThread);
 
-#ifdef ENABLE_TESTS
-  TestPBackground();
-#endif
-
   mWorkerPrivate->AssertIsOnWorkerThread();
 
   {
     nsCycleCollector_startup();
 
     WorkerJSRuntime runtime(mWorkerPrivate);
     nsresult rv = runtime.Initialize(mParentRuntime);
     if (NS_WARN_IF(NS_FAILED(rv))) {
@@ -2738,20 +2668,16 @@ WorkerThreadPrimaryRunnable::Run()
       {
         JSAutoRequest ar(cx);
 
         mWorkerPrivate->DoRunLoop(cx);
 
         JS_ReportPendingException(cx);
       }
 
-#ifdef ENABLE_TESTS
-      TestPBackground();
-#endif
-
       BackgroundChild::CloseForCurrentThread();
 
 #ifdef MOZ_ENABLE_PROFILER_SPS
       if (stack) {
         stack->sampleRuntime(nullptr);
       }
 #endif
     }