--- a/browser/app/nsBrowserApp.cpp
+++ b/browser/app/nsBrowserApp.cpp
@@ -269,20 +269,17 @@ static int do_main(int argc, char* argv[
     if (NS_FAILED(rv)) {
       Output("Couldn't find the application directory.\n");
       return 255;
     }
 
     nsCOMPtr<nsIFile> greDir;
     exeFile->GetParent(getter_AddRefs(greDir));
 #ifdef XP_MACOSX
-    nsCOMPtr<nsIFile> parent;
-    greDir->GetParent(getter_AddRefs(parent));
-    greDir = parent.forget();
-    greDir->AppendNative(NS_LITERAL_CSTRING(kOSXResourcesFolder));
+    greDir->SetNativeLeafName(NS_LITERAL_CSTRING(kOSXResourcesFolder));
 #endif
     nsCOMPtr<nsIFile> appSubdir;
     greDir->Clone(getter_AddRefs(appSubdir));
     appSubdir->Append(NS_LITERAL_STRING(kDesktopFolder));
 
     SetStrongPtr(appData.directory, static_cast<nsIFile*>(appSubdir.get()));
     // xreDirectory already has a refcount from NS_NewLocalFile
     appData.xreDirectory = xreDirectory;

--- a/ipc/glue/GeckoChildProcessHost.cpp
+++ b/ipc/glue/GeckoChildProcessHost.cpp
@@ -127,38 +127,34 @@ GeckoChildProcessHost::~GeckoChildProces
 #endif
 }
 
 //static
 void
 GeckoChildProcessHost::GetPathToBinary(FilePath& exePath)
 {
   if (ShouldHaveDirectoryService()) {
-    MOZ_ASSERT(gGREPath);
+    MOZ_ASSERT(gGREBinPath);
 #ifdef OS_WIN
-    exePath = FilePath(char16ptr_t(gGREPath));
+    exePath = FilePath(char16ptr_t(gGREBinPath));
 #elif MOZ_WIDGET_COCOA
     nsCOMPtr<nsIFile> childProcPath;
-    NS_NewLocalFile(nsDependentString(gGREPath), false,
+    NS_NewLocalFile(nsDependentString(gGREBinPath), false,
                     getter_AddRefs(childProcPath));
     // We need to use an App Bundle on OS X so that we can hide
     // the dock icon. See Bug 557225.
-    nsCOMPtr<nsIFile> tempPath;
-    childProcPath->GetParent(getter_AddRefs(tempPath));
-    childProcPath = tempPath.forget();
-    childProcPath->AppendNative(NS_LITERAL_CSTRING("MacOS"));
     childProcPath->AppendNative(NS_LITERAL_CSTRING("plugin-container.app"));
     childProcPath->AppendNative(NS_LITERAL_CSTRING("Contents"));
     childProcPath->AppendNative(NS_LITERAL_CSTRING("MacOS"));
     nsCString tempCPath;
     childProcPath->GetNativePath(tempCPath);
     exePath = FilePath(tempCPath.get());
 #else
     nsCString path;
-    NS_CopyUnicodeToNative(nsDependentString(gGREPath), path);
+    NS_CopyUnicodeToNative(nsDependentString(gGREBinPath), path);
     exePath = FilePath(path.get());
 #endif
   }
 
   if (exePath.empty()) {
 #ifdef OS_WIN
     exePath = FilePath::FromWStringHack(CommandLine::ForCurrentProcess()->program());
 #else
@@ -543,29 +539,19 @@ GeckoChildProcessHost::PerformAsyncLaunc
   if (privs == base::PRIVILEGES_DEFAULT) {
     privs = DefaultChildPrivileges();
   }
   // XPCOM may not be initialized in some subprocesses.  We don't want
   // to initialize XPCOM just for the directory service, especially
   // since LD_LIBRARY_PATH is already set correctly in subprocesses
   // (meaning that we don't need to set that up in the environment).
   if (ShouldHaveDirectoryService()) {
-    MOZ_ASSERT(gGREPath);
+    MOZ_ASSERT(gGREBinPath);
     nsCString path;
-#ifdef MOZ_WIDGET_COCOA
-    nsCOMPtr<nsIFile> grePath;
-    nsCOMPtr<nsIFile> tempPath;
-    NS_NewLocalFile(nsDependentString(gGREPath), false,
-                    getter_AddRefs(grePath));
-    grePath->GetParent(getter_AddRefs(tempPath));
-    tempPath->AppendNative(NS_LITERAL_CSTRING("MacOS"));
-    tempPath->GetNativePath(path);
-#else
-    NS_CopyUnicodeToNative(nsDependentString(gGREPath), path);
-#endif
+    NS_CopyUnicodeToNative(nsDependentString(gGREBinPath), path);
 # if defined(OS_LINUX) || defined(OS_BSD)
 #  if defined(MOZ_WIDGET_ANDROID)
     path += "/lib";
 #  endif  // MOZ_WIDGET_ANDROID
     const char *ld_library_path = PR_GetEnv("LD_LIBRARY_PATH");
     nsCString new_ld_lib_path;
     if (ld_library_path && *ld_library_path) {
       new_ld_lib_path.Assign(path.get());

--- a/js/xpconnect/src/XPCShellImpl.cpp
+++ b/js/xpconnect/src/XPCShellImpl.cpp
@@ -1272,21 +1272,20 @@ XRE_XPCShellMain(int argc, char **argv, 
 
         argc -= 2;
         argv += 2;
     } else {
 #ifdef XP_MACOSX
         // On OSX, the GreD needs to point to Contents/Resources in the .app
         // bundle. Libraries will be loaded at a relative path to GreD, i.e.
         // ../MacOS.
-        XRE_GetFileFromPath(argv[0], getter_AddRefs(greDir));
-        nsCOMPtr<nsIFile> parentDir;
-        greDir->GetParent(getter_AddRefs(parentDir));
-        parentDir->GetParent(getter_AddRefs(greDir));
-        greDir->AppendNative(NS_LITERAL_CSTRING("Resources"));
+        nsCOMPtr<nsIFile> tmpDir;
+        XRE_GetFileFromPath(argv[0], getter_AddRefs(tmpDir));
+        tmpDir->GetParent(getter_AddRefs(greDir));
+        greDir->SetNativeLeafName(NS_LITERAL_CSTRING("Resources"));
         bool dirExists = false;
         greDir->Exists(&dirExists);
         if (!dirExists) {
             printf("Setting GreD failed.\n");
             return 1;
         }
         dirprovider.SetGREDirs(greDir);
 #else

--- a/security/manager/ssl/tests/unit/head_psm.js
+++ b/security/manager/ssl/tests/unit/head_psm.js
@@ -131,17 +131,17 @@ function _getLibraryFunctionWithNoArgume
 
   // XXX really want to be able to pass specific dlopen flags here.
   let nsslib;
   try {
     nsslib = ctypes.open(path);
   } catch(e) {
     // In case opening the library without a full path fails,
     // try again with a full path.
-    let file = Services.dirsvc.get("GreD", Ci.nsILocalFile);
+    let file = Services.dirsvc.get("GreBinD", Ci.nsILocalFile);
     file.append(path);
     nsslib = ctypes.open(file.path);
   }
 
   let SECStatus = ctypes.int;
   let func = nsslib.declare(functionName, ctypes.default_abi, SECStatus);
   return func;
 }
@@ -355,21 +355,19 @@ function _setupTLSServerTest(serverBinNa
   addCertFromFile(certdb, "tlsserver/test-ca.der", "CTu,u,u");
 
   const CALLBACK_PORT = 8444;
 
   let directoryService = Cc["@mozilla.org/file/directory_service;1"]
                            .getService(Ci.nsIProperties);
   let envSvc = Cc["@mozilla.org/process/environment;1"]
                  .getService(Ci.nsIEnvironment);
-  let greDir = directoryService.get("GreD", Ci.nsIFile);
-  let macOSDir = greDir.parent;
-  macOSDir.append("MacOS");
-  envSvc.set("DYLD_LIBRARY_PATH", macOSDir.path);
-  envSvc.set("LD_LIBRARY_PATH", greDir.path);
+  let greBinDir = directoryService.get("GreBinD", Ci.nsIFile);
+  envSvc.set("DYLD_LIBRARY_PATH", greBinDir.path);
+  envSvc.set("LD_LIBRARY_PATH", greBinDir.path);
   envSvc.set("MOZ_TLS_SERVER_DEBUG_LEVEL", "3");
   envSvc.set("MOZ_TLS_SERVER_CALLBACK_PORT", CALLBACK_PORT);
 
   let httpServer = new HttpServer();
   httpServer.registerPathHandler("/",
       function handleServerCallback(aRequest, aResponse) {
         aResponse.setStatusLine(aRequest.httpVersion, 200, "OK");
         aResponse.setHeader("Content-Type", "text/plain");

--- a/startupcache/test/TestStartupCache.cpp
+++ b/startupcache/test/TestStartupCache.cpp
@@ -409,24 +409,16 @@ int main(int argc, char** argv)
   
   int rv = 0;
   nsresult scrv;
 
   // Register TestStartupCacheTelemetry
   nsCOMPtr<nsIFile> manifest;
   scrv = NS_GetSpecialDirectory(NS_GRE_DIR,
                                 getter_AddRefs(manifest));
-#ifdef XP_MACOSX
-  if (NS_SUCCEEDED(scrv)) {
-    nsCOMPtr<nsIFile> parent;
-    manifest->GetParent(getter_AddRefs(parent));
-    parent->AppendNative(NS_LITERAL_CSTRING("MacOS"));
-    manifest = parent.forget();
-  }
-#endif
   if (NS_FAILED(scrv)) {
     fail("NS_XPCOM_CURRENT_PROCESS_DIR");
     return 1;
   }
 
   manifest->AppendNative(NS_LITERAL_CSTRING("TestStartupCacheTelemetry.manifest"));
   XRE_AddManifestLocation(NS_COMPONENT_LOCATION, manifest);
 

--- a/xpcom/build/XPCOMInit.cpp
+++ b/xpcom/build/XPCOMInit.cpp
@@ -269,17 +269,17 @@ nsXPTIInterfaceInfoManagerGetSingleton(n
   }
 
   return iim->QueryInterface(aIID, aInstancePtr);
 }
 
 nsComponentManagerImpl* nsComponentManagerImpl::gComponentManager = nullptr;
 bool gXPCOMShuttingDown = false;
 bool gXPCOMThreadsShutDown = false;
-char16_t* gGREPath = nullptr;
+char16_t* gGREBinPath = nullptr;
 
 static NS_DEFINE_CID(kComponentManagerCID, NS_COMPONENTMANAGER_CID);
 static NS_DEFINE_CID(kINIParserFactoryCID, NS_INIPARSERFACTORY_CID);
 static NS_DEFINE_CID(kSimpleUnicharStreamFactoryCID,
                      NS_SIMPLE_UNICHAR_STREAM_FACTORY_CID);
 
 NS_DEFINE_NAMED_CID(NS_CHROMEREGISTRY_CID);
 NS_DEFINE_NAMED_CID(NS_CHROMEPROTOCOLHANDLER_CID);
@@ -579,36 +579,25 @@ NS_InitXPCOM2(nsIServiceManager** aResul
   if (aAppFileLocationProvider) {
     rv = nsDirectoryService::gService->RegisterProvider(aAppFileLocationProvider);
     if (NS_FAILED(rv)) {
       return rv;
     }
   }
 
   nsCOMPtr<nsIFile> xpcomLib;
-  nsDirectoryService::gService->Get(NS_GRE_DIR,
+  nsDirectoryService::gService->Get(NS_GRE_BIN_DIR,
                                     NS_GET_IID(nsIFile),
                                     getter_AddRefs(xpcomLib));
   MOZ_ASSERT(xpcomLib);
 
-  // set gGREPath
+  // set gGREBinPath
   nsAutoString path;
   xpcomLib->GetPath(path);
-  gGREPath = ToNewUnicode(path);
-
-#ifdef XP_MACOSX
-  nsCOMPtr<nsIFile> parent;
-  xpcomLib->GetParent(getter_AddRefs(parent));
-  parent->AppendNative(NS_LITERAL_CSTRING("MacOS"));
-  bool pathExists = false;
-  parent->Exists(&pathExists);
-  if (pathExists) {
-      xpcomLib = parent.forget();
-  }
-#endif
+  gGREBinPath = ToNewUnicode(path);
 
   xpcomLib->AppendNative(nsDependentCString(XPCOM_DLL));
   nsDirectoryService::gService->Set(NS_XPCOM_LIBRARY_FILE, xpcomLib);
 
   if (!mozilla::Omnijar::IsInitialized()) {
     mozilla::Omnijar::Init();
   }
 
@@ -910,18 +899,18 @@ ShutdownXPCOM(nsIServiceManager* aServMg
   // Shutdown global servicemanager
   if (nsComponentManagerImpl::gComponentManager) {
     nsComponentManagerImpl::gComponentManager->FreeServices();
   }
 
   // Release the directory service
   NS_IF_RELEASE(nsDirectoryService::gService);
 
-  NS_Free(gGREPath);
-  gGREPath = nullptr;
+  NS_Free(gGREBinPath);
+  gGREBinPath = nullptr;
 
   if (moduleLoaders) {
     bool more;
     nsCOMPtr<nsISupports> el;
     while (NS_SUCCEEDED(moduleLoaders->HasMoreElements(&more)) && more) {
       moduleLoaders->GetNext(getter_AddRefs(el));
 
       // Don't worry about weak-reference observers here: there is

--- a/xpcom/build/nsXPCOMPrivate.h
+++ b/xpcom/build/nsXPCOMPrivate.h
@@ -295,17 +295,19 @@ void LogTerm();
 #define MAXPATHLEN CCHMAXPATH
 #else
 #define MAXPATHLEN 1024
 #endif
 #endif
 
 extern bool gXPCOMShuttingDown;
 extern bool gXPCOMThreadsShutDown;
-extern char16_t* gGREPath; // Needed by the IPC layer from off the main thread
+
+// Needed by the IPC layer from off the main thread
+extern char16_t* gGREBinPath;
 
 namespace mozilla {
 namespace services {
 
 /**
  * Clears service cache, sets gXPCOMShuttingDown
  */
 void Shutdown();

--- a/xpcom/tests/TestHarness.h
+++ b/xpcom/tests/TestHarness.h
@@ -194,16 +194,41 @@ class ScopedXPCOM : public nsIDirectoryS
         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)
     {
       // If we were supplied a directory service provider, ask it first.
       if (mDirSvcProvider &&
@@ -221,25 +246,30 @@ class ScopedXPCOM : public nsIDirectoryS
 
         nsCOMPtr<nsIFile> clone;
         nsresult rv = profD->Clone(getter_AddRefs(clone));
         NS_ENSURE_SUCCESS(rv, rv);
 
         *_persistent = true;
         clone.forget(_result);
         return NS_OK;
-      }
-
-      if (0 == strcmp(aProperty, NS_GRE_DIR)) {
+      } 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
 
@@ -256,16 +286,17 @@ class ScopedXPCOM : public nsIDirectoryS
    }
 
   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
 )
 

--- a/xpcom/tests/unit/head_xpcom.js
+++ b/xpcom/tests/unit/head_xpcom.js
@@ -10,17 +10,15 @@ function get_test_program(prog)
 }
 
 function set_process_running_environment()
 {
   var envSvc = Components.classes["@mozilla.org/process/environment;1"].
     getService(Components.interfaces.nsIEnvironment);
   var dirSvc = Components.classes["@mozilla.org/file/directory_service;1"].
     getService(Components.interfaces.nsIProperties);
-  var greDir = dirSvc.get("GreD", Components.interfaces.nsIFile);
-  var macOSDir = greDir.parent;
-  macOSDir.append("MacOS");
-  envSvc.set("DYLD_LIBRARY_PATH", macOSDir.path);
+  var greBinDir = dirSvc.get("GreBinD", Components.interfaces.nsIFile);
+  envSvc.set("DYLD_LIBRARY_PATH", greBinDir.path);
   // For Linux
-  envSvc.set("LD_LIBRARY_PATH", greDir.path);
+  envSvc.set("LD_LIBRARY_PATH", greBinDir.path);
   //XXX: handle windows
 }