--- a/dom/localstorage/LocalStorageCommon.cpp
+++ b/dom/localstorage/LocalStorageCommon.cpp
@@ -1,19 +1,23 @@
 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
 /* 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 "LocalStorageCommon.h"
 
+#include "mozilla/net/MozURL.h"
+
 namespace mozilla {
 namespace dom {
 
+using namespace mozilla::net;
+
 namespace {
 
 Atomic<int32_t> gNextGenLocalStorageEnabled(-1);
 
 }  // namespace
 
 const char16_t* kLocalStorageType = u"localStorage";
 
@@ -29,10 +33,92 @@ bool NextGenLocalStorageEnabled() {
 }
 
 bool CachedNextGenLocalStorageEnabled() {
   MOZ_ASSERT(gNextGenLocalStorageEnabled != -1);
 
   return !!gNextGenLocalStorageEnabled;
 }
 
+nsresult GenerateOriginKey2(const PrincipalInfo& aPrincipalInfo,
+                            nsACString& aOriginAttrSuffix,
+                            nsACString& aOriginKey) {
+  OriginAttributes attrs;
+  nsCString spec;
+
+  switch (aPrincipalInfo.type()) {
+    case PrincipalInfo::TNullPrincipalInfo: {
+      const NullPrincipalInfo& info = aPrincipalInfo.get_NullPrincipalInfo();
+
+      attrs = info.attrs();
+      spec = info.spec();
+
+      break;
+    }
+
+    case PrincipalInfo::TContentPrincipalInfo: {
+      const ContentPrincipalInfo& info =
+          aPrincipalInfo.get_ContentPrincipalInfo();
+
+      attrs = info.attrs();
+      spec = info.spec();
+
+      break;
+    }
+
+    default: {
+      spec.SetIsVoid(true);
+
+      break;
+    }
+  }
+
+  if (spec.IsVoid()) {
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  attrs.CreateSuffix(aOriginAttrSuffix);
+
+  RefPtr<MozURL> specURL;
+  nsresult rv = MozURL::Init(getter_AddRefs(specURL), spec);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  nsCString host(specURL->Host());
+  uint32_t length = host.Length();
+  if (length > 0 && host.CharAt(0) == '[' && host.CharAt(length - 1) == ']') {
+    host = Substring(host, 1, length - 2);
+  }
+
+  nsCString domainOrigin(host);
+
+  if (domainOrigin.IsEmpty()) {
+    // For the file:/// protocol use the exact directory as domain.
+    if (specURL->Scheme().EqualsLiteral("file")) {
+      domainOrigin.Assign(specURL->Directory());
+    }
+  }
+
+  // Append reversed domain
+  nsAutoCString reverseDomain;
+  rv = CreateReversedDomain(domainOrigin, reverseDomain);
+  if (NS_FAILED(rv)) {
+    return rv;
+  }
+
+  aOriginKey.Append(reverseDomain);
+
+  // Append scheme
+  aOriginKey.Append(':');
+  aOriginKey.Append(specURL->Scheme());
+
+  // Append port if any
+  int32_t port = specURL->RealPort();
+  if (port != -1) {
+    aOriginKey.Append(nsPrintfCString(":%d", port));
+  }
+
+  return NS_OK;
+}
+
 }  // namespace dom
 }  // namespace mozilla

--- a/dom/localstorage/LocalStorageCommon.h
+++ b/dom/localstorage/LocalStorageCommon.h
@@ -176,17 +176,27 @@
  * ~~~~~~~~~~~~~~~~~~~~~
  *
  * The local storage manager exposes some of the features that need to be
  * available only in the chrome code or tests. The manager is represented by
  * the "LocalStorageManager2" class that implements the "nsIDOMStorageManager"
  * interface.
  */
 
+#include "mozilla/Attributes.h"
+#include "nsString.h"
+
 namespace mozilla {
+
+namespace ipc {
+
+class PrincipalInfo;
+
+}  // namespace ipc
+
 namespace dom {
 
 extern const char16_t* kLocalStorageType;
 
 /**
  * Convenience data-structure to make it easier to track whether a value has
  * changed and what its previous value was for notification purposes.  Instances
  * are created on the stack by LSObject and passed to LSDatabase which in turn
@@ -215,12 +225,16 @@ class MOZ_STACK_CLASS LSNotifyInfo {
  */
 bool NextGenLocalStorageEnabled();
 
 /**
  * Cached any-thread version of NextGenLocalStorageEnabled().
  */
 bool CachedNextGenLocalStorageEnabled();
 
+nsresult GenerateOriginKey2(const mozilla::ipc::PrincipalInfo& aPrincipalInfo,
+                            nsACString& aOriginAttrSuffix,
+                            nsACString& aOriginKey);
+
 }  // namespace dom
 }  // namespace mozilla
 
 #endif  // mozilla_dom_localstorage_LocalStorageCommon_h

--- a/dom/localstorage/moz.build
+++ b/dom/localstorage/moz.build
@@ -7,16 +7,18 @@
 XPCSHELL_TESTS_MANIFESTS += [
     'test/unit/xpcshell.ini'
 ]
 
 TEST_HARNESS_FILES.xpcshell.dom.localstorage.test.unit += [
     'test/unit/databaseShadowing-shared.js',
 ]
 
+TEST_DIRS += ['test/gtest']
+
 XPIDL_SOURCES += [
     'nsILocalStorageManager.idl',
 ]
 
 XPIDL_MODULE = 'dom_localstorage'
 
 EXPORTS.mozilla.dom.localstorage += [
     'ActorsParent.h',

new file mode 100644
--- /dev/null
+++ b/dom/localstorage/test/gtest/TestLocalStorage.cpp
@@ -0,0 +1,113 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* 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 "gtest/gtest.h"
+#include "mozilla/NullPrincipal.h"
+#include "mozilla/dom/LocalStorageCommon.h"
+#include "mozilla/dom/StorageUtils.h"
+#include "mozilla/ipc/BackgroundUtils.h"
+#include "mozilla/ipc/PBackgroundSharedTypes.h"
+#include "nsCOMPtr.h"
+#include "nsContentUtils.h"
+#include "nsIURI.h"
+#include "nsNetUtil.h"
+
+using namespace mozilla;
+using namespace mozilla::dom;
+using namespace mozilla::dom::StorageUtils;
+using namespace mozilla::ipc;
+
+namespace {
+
+struct OriginKeyTest {
+  const char* mSpec;
+  const char* mOriginKey;
+};
+
+already_AddRefed<nsIPrincipal> GetCodebasePrincipal(const char* aSpec) {
+  nsCOMPtr<nsIURI> uri;
+  nsresult rv = NS_NewURI(getter_AddRefs(uri), nsDependentCString(aSpec));
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return nullptr;
+  }
+
+  OriginAttributes attrs;
+
+  nsCOMPtr<nsIPrincipal> principal =
+      BasePrincipal::CreateCodebasePrincipal(uri, attrs);
+
+  return principal.forget();
+}
+
+void CheckGeneratedOriginKey(nsIPrincipal* aPrincipal, const char* aOriginKey) {
+  nsCString originAttrSuffix;
+  nsCString originKey;
+  nsresult rv = GenerateOriginKey(aPrincipal, originAttrSuffix, originKey);
+  if (aOriginKey) {
+    ASSERT_EQ(rv, NS_OK) << "GenerateOriginKey should not fail";
+    EXPECT_TRUE(originKey == nsDependentCString(aOriginKey));
+  } else {
+    ASSERT_NE(rv, NS_OK) << "GenerateOriginKey should fail";
+  }
+
+  PrincipalInfo principalInfo;
+  rv = PrincipalToPrincipalInfo(aPrincipal, &principalInfo);
+  ASSERT_EQ(rv, NS_OK) << "PrincipalToPrincipalInfo should not fail";
+
+  originKey.Truncate();
+  rv = GenerateOriginKey2(principalInfo, originAttrSuffix, originKey);
+  if (aOriginKey) {
+    ASSERT_EQ(rv, NS_OK) << "GenerateOriginKey2 should not fail";
+    EXPECT_TRUE(originKey == nsDependentCString(aOriginKey));
+  } else {
+    ASSERT_NE(rv, NS_OK) << "GenerateOriginKey2 should fail";
+  }
+}
+
+}  // namespace
+
+TEST(LocalStorage, OriginKey) {
+  // Check the system principal.
+  nsCOMPtr<nsIScriptSecurityManager> secMan =
+      nsContentUtils::GetSecurityManager();
+  ASSERT_TRUE(secMan) << "GetSecurityManager() should not fail";
+
+  nsCOMPtr<nsIPrincipal> principal;
+  secMan->GetSystemPrincipal(getter_AddRefs(principal));
+  ASSERT_TRUE(principal) << "GetSystemPrincipal() should not fail";
+
+  CheckGeneratedOriginKey(principal, nullptr);
+
+  // Check the null principal.
+  principal = NullPrincipal::CreateWithoutOriginAttributes();
+  ASSERT_TRUE(principal) << "CreateWithoutOriginAttributes() should not fail";
+
+  CheckGeneratedOriginKey(principal, nullptr);
+
+  // Check content principals.
+  static const OriginKeyTest tests[] = {
+      {"http://www.mozilla.org", "gro.allizom.www.:http:80"},
+      {"https://www.mozilla.org", "gro.allizom.www.:https:443"},
+      {"http://www.mozilla.org:32400", "gro.allizom.www.:http:32400"},
+      {"file:///Users/Joe/Sites/", "/setiS/eoJ/sresU/.:file"},
+      {"file:///Users/Joe/Sites/#foo", "/setiS/eoJ/sresU/.:file"},
+      {"file:///Users/Joe/Sites/?foo", "/setiS/eoJ/sresU/.:file"},
+      {"file:///Users/Joe/Sites", "/eoJ/sresU/.:file"},
+      {"file:///Users/Joe/Sites#foo", "/eoJ/sresU/.:file"},
+      {"file:///Users/Joe/Sites?foo", "/eoJ/sresU/.:file"},
+      {"moz-extension://53711a8f-65ed-e742-9671-1f02e267c0bc/"
+       "_generated_background_page.html",
+       "cb0c762e20f1-1769-247e-de56-f8a11735.:moz-extension"},
+      {"http://[::1]:8/test.html", "1::.:http:8"},
+  };
+
+  for (const auto& test : tests) {
+    principal = GetCodebasePrincipal(test.mSpec);
+    ASSERT_TRUE(principal) << "GetCodebasePrincipal() should not fail";
+
+    CheckGeneratedOriginKey(principal, test.mOriginKey);
+  }
+}

new file mode 100644
--- /dev/null
+++ b/dom/localstorage/test/gtest/moz.build
@@ -0,0 +1,17 @@
+# -*- 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/.
+
+UNIFIED_SOURCES = [
+    'TestLocalStorage.cpp',
+]
+
+include('/ipc/chromium/chromium-config.mozbuild')
+
+FINAL_LIBRARY = 'xul-gtest'
+
+LOCAL_INCLUDES += [
+    '/dom/localstorage',
+]

--- a/dom/storage/StorageUtils.h
+++ b/dom/storage/StorageUtils.h
@@ -2,16 +2,18 @@
 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
 /* 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_dom_StorageUtils_h
 #define mozilla_dom_StorageUtils_h
 
+#include "nsStringFwd.h"
+
 class nsIPrincipal;
 
 namespace mozilla {
 namespace dom {
 namespace StorageUtils {
 
 nsresult GenerateOriginKey(nsIPrincipal* aPrincipal,
                            nsACString& aOriginAttrSuffix,