1 files changed, 688 insertions, 0 deletions
diff --git a/dom/base/ScreenOrientation.cpp b/dom/base/ScreenOrientation.cpp
new file mode 100644
index 000000000..bb3ccf5c3
--- /dev/null
+++ b/dom/base/ScreenOrientation.cpp
@@ -0,0 +1,688 @@
+/* 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 "ScreenOrientation.h"
+#include "nsIDeviceSensors.h"
+#include "nsIDocShell.h"
+#include "nsIDocument.h"
+#include "nsGlobalWindow.h"
+#include "nsSandboxFlags.h"
+#include "nsScreen.h"
+
+#include "mozilla/DOMEventTargetHelper.h"
+#include "mozilla/Hal.h"
+#include "mozilla/Preferences.h"
+
+#include "mozilla/dom/Promise.h"
+#include "nsContentUtils.h"
+
+using namespace mozilla;
+using namespace mozilla::dom;
+
+NS_IMPL_CYCLE_COLLECTION_INHERITED(ScreenOrientation,
+                                   DOMEventTargetHelper,
+                                   mScreen);
+
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION_INHERITED(ScreenOrientation)
+NS_INTERFACE_MAP_END_INHERITING(DOMEventTargetHelper)
+
+NS_IMPL_ADDREF_INHERITED(ScreenOrientation, DOMEventTargetHelper)
+NS_IMPL_RELEASE_INHERITED(ScreenOrientation, DOMEventTargetHelper)
+
+static OrientationType
+InternalOrientationToType(ScreenOrientationInternal aOrientation)
+{
+  switch (aOrientation) {
+  case eScreenOrientation_PortraitPrimary:
+    return OrientationType::Portrait_primary;
+  case eScreenOrientation_PortraitSecondary:
+    return OrientationType::Portrait_secondary;
+  case eScreenOrientation_LandscapePrimary:
+    return OrientationType::Landscape_primary;
+  case eScreenOrientation_LandscapeSecondary:
+    return OrientationType::Landscape_secondary;
+  default:
+    MOZ_CRASH("Bad aOrientation value");
+  }
+}
+
+static ScreenOrientationInternal
+OrientationTypeToInternal(OrientationType aOrientation)
+{
+  switch (aOrientation) {
+  case OrientationType::Portrait_primary:
+    return eScreenOrientation_PortraitPrimary;
+  case OrientationType::Portrait_secondary:
+    return eScreenOrientation_PortraitSecondary;
+  case OrientationType::Landscape_primary:
+    return eScreenOrientation_LandscapePrimary;
+  case OrientationType::Landscape_secondary:
+    return eScreenOrientation_LandscapeSecondary;
+  default:
+    MOZ_CRASH("Bad aOrientation value");
+  }
+}
+
+ScreenOrientation::ScreenOrientation(nsPIDOMWindowInner* aWindow, nsScreen* aScreen)
+  : DOMEventTargetHelper(aWindow), mScreen(aScreen)
+{
+  MOZ_ASSERT(aWindow);
+  MOZ_ASSERT(aScreen);
+
+  hal::RegisterScreenConfigurationObserver(this);
+
+  hal::ScreenConfiguration config;
+  hal::GetCurrentScreenConfiguration(&config);
+  mType = InternalOrientationToType(config.orientation());
+  mAngle = config.angle();
+
+  nsIDocument* doc = GetResponsibleDocument();
+  if (doc) {
+    doc->SetCurrentOrientation(mType, mAngle);
+  }
+}
+
+ScreenOrientation::~ScreenOrientation()
+{
+  hal::UnregisterScreenConfigurationObserver(this);
+  MOZ_ASSERT(!mFullScreenListener);
+}
+
+class ScreenOrientation::FullScreenEventListener final : public nsIDOMEventListener
+{
+  ~FullScreenEventListener() {}
+public:
+  FullScreenEventListener() {}
+
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSIDOMEVENTLISTENER
+};
+
+class ScreenOrientation::VisibleEventListener final : public nsIDOMEventListener
+{
+  ~VisibleEventListener() {}
+public:
+  VisibleEventListener() {}
+
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSIDOMEVENTLISTENER
+};
+
+class ScreenOrientation::LockOrientationTask final : public nsIRunnable
+{
+  ~LockOrientationTask();
+public:
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSIRUNNABLE
+
+  LockOrientationTask(ScreenOrientation* aScreenOrientation,
+                      Promise* aPromise,
+                      ScreenOrientationInternal aOrientationLock,
+                      nsIDocument* aDocument,
+                      bool aIsFullScreen);
+protected:
+  bool OrientationLockContains(OrientationType aOrientationType);
+
+  RefPtr<ScreenOrientation> mScreenOrientation;
+  RefPtr<Promise> mPromise;
+  ScreenOrientationInternal mOrientationLock;
+  nsCOMPtr<nsIDocument> mDocument;
+  bool mIsFullScreen;
+};
+
+NS_IMPL_ISUPPORTS(ScreenOrientation::LockOrientationTask, nsIRunnable)
+
+ScreenOrientation::LockOrientationTask::LockOrientationTask(
+  ScreenOrientation* aScreenOrientation, Promise* aPromise,
+  ScreenOrientationInternal aOrientationLock,
+  nsIDocument* aDocument, bool aIsFullScreen)
+  : mScreenOrientation(aScreenOrientation), mPromise(aPromise),
+    mOrientationLock(aOrientationLock), mDocument(aDocument),
+    mIsFullScreen(aIsFullScreen)
+{
+  MOZ_ASSERT(aScreenOrientation);
+  MOZ_ASSERT(aPromise);
+  MOZ_ASSERT(aDocument);
+}
+
+ScreenOrientation::LockOrientationTask::~LockOrientationTask()
+{
+}
+
+bool
+ScreenOrientation::LockOrientationTask::OrientationLockContains(
+  OrientationType aOrientationType)
+{
+  return mOrientationLock & OrientationTypeToInternal(aOrientationType);
+}
+
+NS_IMETHODIMP
+ScreenOrientation::LockOrientationTask::Run()
+{
+  // Step to lock the orientation as defined in the spec.
+
+  if (mDocument->GetOrientationPendingPromise() != mPromise) {
+    // The document's pending promise is not associated with this task
+    // to lock orientation. There has since been another request to
+    // lock orientation, thus we don't need to do anything. Old promise
+    // should be been rejected.
+    return NS_OK;
+  }
+
+  if (mDocument->Hidden()) {
+    // Active orientation lock is not the document's orientation lock.
+    mPromise->MaybeResolveWithUndefined();
+    mDocument->SetOrientationPendingPromise(nullptr);
+    return NS_OK;
+  }
+
+  if (mOrientationLock == eScreenOrientation_None) {
+    mScreenOrientation->UnlockDeviceOrientation();
+    mPromise->MaybeResolveWithUndefined();
+    mDocument->SetOrientationPendingPromise(nullptr);
+    return NS_OK;
+  }
+
+  ErrorResult rv;
+  bool result = mScreenOrientation->LockDeviceOrientation(mOrientationLock,
+                                                          mIsFullScreen, rv);
+  if (NS_WARN_IF(rv.Failed())) {
+    return rv.StealNSResult();
+  }
+
+  if (NS_WARN_IF(!result)) {
+    mPromise->MaybeReject(NS_ERROR_UNEXPECTED);
+    mDocument->SetOrientationPendingPromise(nullptr);
+    return NS_OK;
+  }
+
+  if (OrientationLockContains(mDocument->CurrentOrientationType()) ||
+      (mOrientationLock == eScreenOrientation_Default &&
+       mDocument->CurrentOrientationAngle() == 0)) {
+    // Orientation lock will not cause an orientation change.
+    mPromise->MaybeResolveWithUndefined();
+    mDocument->SetOrientationPendingPromise(nullptr);
+  }
+
+  return NS_OK;
+}
+
+already_AddRefed<Promise>
+ScreenOrientation::Lock(OrientationLockType aOrientation, ErrorResult& aRv)
+{
+  ScreenOrientationInternal orientation = eScreenOrientation_None;
+
+  switch (aOrientation) {
+  case OrientationLockType::Any:
+    orientation = eScreenOrientation_PortraitPrimary |
+                  eScreenOrientation_PortraitSecondary |
+                  eScreenOrientation_LandscapePrimary |
+                  eScreenOrientation_LandscapeSecondary;
+    break;
+  case OrientationLockType::Natural:
+    orientation |= eScreenOrientation_Default;
+    break;
+  case OrientationLockType::Landscape:
+    orientation = eScreenOrientation_LandscapePrimary |
+                  eScreenOrientation_LandscapeSecondary;
+    break;
+  case OrientationLockType::Portrait:
+    orientation = eScreenOrientation_PortraitPrimary |
+                  eScreenOrientation_PortraitSecondary;
+    break;
+  case OrientationLockType::Portrait_primary:
+    orientation = eScreenOrientation_PortraitPrimary;
+    break;
+  case OrientationLockType::Portrait_secondary:
+    orientation = eScreenOrientation_PortraitSecondary;
+    break;
+  case OrientationLockType::Landscape_primary:
+    orientation = eScreenOrientation_LandscapePrimary;
+    break;
+  case OrientationLockType::Landscape_secondary:
+    orientation = eScreenOrientation_LandscapeSecondary;
+    break;
+  default:
+    NS_WARNING("Unexpected orientation type");
+    aRv.Throw(NS_ERROR_UNEXPECTED);
+    return nullptr;
+  }
+
+  return LockInternal(orientation, aRv);
+}
+
+static inline void
+AbortOrientationPromises(nsIDocShell* aDocShell)
+{
+  MOZ_ASSERT(aDocShell);
+
+  nsIDocument* doc = aDocShell->GetDocument();
+  if (doc) {
+    Promise* promise = doc->GetOrientationPendingPromise();
+    if (promise) {
+      promise->MaybeReject(NS_ERROR_DOM_ABORT_ERR);
+      doc->SetOrientationPendingPromise(nullptr);
+    }
+  }
+
+  int32_t childCount;
+  aDocShell->GetChildCount(&childCount);
+  for (int32_t i = 0; i < childCount; i++) {
+    nsCOMPtr<nsIDocShellTreeItem> child;
+    if (NS_SUCCEEDED(aDocShell->GetChildAt(i, getter_AddRefs(child)))) {
+      nsCOMPtr<nsIDocShell> childShell(do_QueryInterface(child));
+      if (childShell) {
+        AbortOrientationPromises(childShell);
+      }
+    }
+  }
+}
+
+already_AddRefed<Promise>
+ScreenOrientation::LockInternal(ScreenOrientationInternal aOrientation, ErrorResult& aRv)
+{
+  // Steps to apply an orientation lock as defined in spec.
+
+  nsIDocument* doc = GetResponsibleDocument();
+  if (NS_WARN_IF(!doc)) {
+    aRv.Throw(NS_ERROR_UNEXPECTED);
+    return nullptr;
+  }
+
+  nsCOMPtr<nsPIDOMWindowInner> owner = GetOwner();
+  if (NS_WARN_IF(!owner)) {
+    aRv.Throw(NS_ERROR_UNEXPECTED);
+    return nullptr;
+  }
+
+  nsCOMPtr<nsIDocShell> docShell = owner->GetDocShell();
+  if (NS_WARN_IF(!docShell)) {
+    aRv.Throw(NS_ERROR_UNEXPECTED);
+    return nullptr;
+  }
+
+  nsCOMPtr<nsIGlobalObject> go = do_QueryInterface(owner);
+  MOZ_ASSERT(go);
+  RefPtr<Promise> p = Promise::Create(go, aRv);
+  if (NS_WARN_IF(aRv.Failed())) {
+    return nullptr;
+  }
+
+#if !defined(MOZ_WIDGET_ANDROID) && !defined(MOZ_WIDGET_GONK)
+  // User agent does not support locking the screen orientation.
+  p->MaybeReject(NS_ERROR_DOM_NOT_SUPPORTED_ERR);
+  return p.forget();
+#else
+  LockPermission perm = GetLockOrientationPermission(true);
+  if (perm == LOCK_DENIED) {
+    p->MaybeReject(NS_ERROR_DOM_SECURITY_ERR);
+    return p.forget();
+  }
+
+  nsCOMPtr<nsIDocShellTreeItem> root;
+  docShell->GetSameTypeRootTreeItem(getter_AddRefs(root));
+  nsCOMPtr<nsIDocShell> rootShell(do_QueryInterface(root));
+  if (!rootShell) {
+    aRv.Throw(NS_ERROR_UNEXPECTED);
+    return nullptr;
+  }
+
+  rootShell->SetOrientationLock(aOrientation);
+  AbortOrientationPromises(rootShell);
+
+  doc->SetOrientationPendingPromise(p);
+
+  nsCOMPtr<nsIRunnable> lockOrientationTask =
+    new LockOrientationTask(this, p, aOrientation, doc,
+                            perm == FULLSCREEN_LOCK_ALLOWED);
+  aRv = NS_DispatchToMainThread(lockOrientationTask);
+  if (NS_WARN_IF(aRv.Failed())) {
+    return nullptr;
+  }
+
+  return p.forget();
+#endif
+}
+
+bool
+ScreenOrientation::LockDeviceOrientation(ScreenOrientationInternal aOrientation,
+                                         bool aIsFullScreen, ErrorResult& aRv)
+{
+  if (!GetOwner()) {
+    aRv.Throw(NS_ERROR_UNEXPECTED);
+    return false;
+  }
+
+  nsCOMPtr<EventTarget> target = do_QueryInterface(GetOwner()->GetDoc());
+  // We need to register a listener so we learn when we leave full-screen
+  // and when we will have to unlock the screen.
+  // This needs to be done before LockScreenOrientation call to make sure
+  // the locking can be unlocked.
+  if (aIsFullScreen && !target) {
+    return false;
+  }
+
+  if (NS_WARN_IF(!hal::LockScreenOrientation(aOrientation))) {
+    return false;
+  }
+
+  // We are fullscreen and lock has been accepted.
+  if (aIsFullScreen && !mFullScreenListener) {
+    mFullScreenListener = new FullScreenEventListener();
+    aRv = target->AddSystemEventListener(NS_LITERAL_STRING("fullscreenchange"),
+                                         mFullScreenListener, /* useCapture = */ true);
+    if (NS_WARN_IF(aRv.Failed())) {
+      return false;
+    }
+  }
+
+  return true;
+}
+
+void
+ScreenOrientation::Unlock(ErrorResult& aRv)
+{
+  RefPtr<Promise> p = LockInternal(eScreenOrientation_None, aRv);
+}
+
+void
+ScreenOrientation::UnlockDeviceOrientation()
+{
+  hal::UnlockScreenOrientation();
+
+  if (!mFullScreenListener || !GetOwner()) {
+    mFullScreenListener = nullptr;
+    return;
+  }
+
+  // Remove event listener in case of fullscreen lock.
+  nsCOMPtr<EventTarget> target = do_QueryInterface(GetOwner()->GetDoc());
+  if (target) {
+    DebugOnly<nsresult> rv =
+      target->RemoveSystemEventListener(NS_LITERAL_STRING("fullscreenchange"),
+                                        mFullScreenListener,
+                                        /* useCapture */ true);
+    NS_WARNING_ASSERTION(NS_SUCCEEDED(rv), "RemoveSystemEventListener failed");
+  }
+
+  mFullScreenListener = nullptr;
+}
+
+OrientationType
+ScreenOrientation::DeviceType() const
+{
+  return ShouldResistFingerprinting() ? OrientationType::Landscape_primary
+                                      : mType;
+}
+
+uint16_t
+ScreenOrientation::DeviceAngle() const
+{
+  return ShouldResistFingerprinting() ? 0 : mAngle;
+}
+
+OrientationType
+ScreenOrientation::GetType(ErrorResult& aRv) const
+{
+  if (ShouldResistFingerprinting()) {
+    return OrientationType::Landscape_primary;
+  }
+
+  nsIDocument* doc = GetResponsibleDocument();
+  if (!doc) {
+    aRv.Throw(NS_ERROR_UNEXPECTED);
+    return OrientationType::Portrait_primary;
+  }
+
+  return doc->CurrentOrientationType();
+}
+
+uint16_t
+ScreenOrientation::GetAngle(ErrorResult& aRv) const
+{
+  if (ShouldResistFingerprinting()) {
+    return 0;
+  }
+
+  nsIDocument* doc = GetResponsibleDocument();
+  if (!doc) {
+    aRv.Throw(NS_ERROR_UNEXPECTED);
+    return 0;
+  }
+
+  return doc->CurrentOrientationAngle();
+}
+
+ScreenOrientation::LockPermission
+ScreenOrientation::GetLockOrientationPermission(bool aCheckSandbox) const
+{
+  nsCOMPtr<nsPIDOMWindowInner> owner = GetOwner();
+  if (!owner) {
+    return LOCK_DENIED;
+  }
+
+  // Chrome can always lock the screen orientation.
+  nsIDocShell* docShell = owner->GetDocShell();
+  if (docShell && docShell->ItemType() == nsIDocShellTreeItem::typeChrome) {
+    return LOCK_ALLOWED;
+  }
+
+  nsCOMPtr<nsIDocument> doc = owner->GetDoc();
+  if (!doc || doc->Hidden()) {
+    return LOCK_DENIED;
+  }
+
+  // Sandboxed without "allow-orientation-lock"
+  if (aCheckSandbox && doc->GetSandboxFlags() & SANDBOXED_ORIENTATION_LOCK) {
+    return LOCK_DENIED;
+  }
+
+  // Apps can always lock the screen orientation.
+  if (doc->NodePrincipal()->GetAppStatus() >=
+        nsIPrincipal::APP_STATUS_INSTALLED) {
+    return LOCK_ALLOWED;
+  }
+
+  if (Preferences::GetBool("dom.screenorientation.testing.non_fullscreen_lock_allow",
+                           false)) {
+    return LOCK_ALLOWED;
+  }
+
+  // Other content must be full-screen in order to lock orientation.
+  return doc->Fullscreen() ? FULLSCREEN_LOCK_ALLOWED : LOCK_DENIED;
+}
+
+nsIDocument*
+ScreenOrientation::GetResponsibleDocument() const
+{
+  nsCOMPtr<nsPIDOMWindowInner> owner = GetOwner();
+  if (!owner) {
+    return nullptr;
+  }
+
+  return owner->GetDoc();
+}
+
+void
+ScreenOrientation::Notify(const hal::ScreenConfiguration& aConfiguration)
+{
+  if (ShouldResistFingerprinting()) {
+    return;
+  }
+
+  nsIDocument* doc = GetResponsibleDocument();
+  if (!doc) {
+    return;
+  }
+
+  ScreenOrientationInternal orientation = aConfiguration.orientation();
+  if (orientation != eScreenOrientation_PortraitPrimary &&
+      orientation != eScreenOrientation_PortraitSecondary &&
+      orientation != eScreenOrientation_LandscapePrimary &&
+      orientation != eScreenOrientation_LandscapeSecondary) {
+    // The platform may notify of some other values from
+    // an orientation lock, but we only care about real
+    // changes to screen orientation which result in one of
+    // the values we care about.
+    return;
+  }
+
+  OrientationType previousOrientation = mType;
+  mAngle = aConfiguration.angle();
+  mType = InternalOrientationToType(orientation);
+
+  DebugOnly<nsresult> rv;
+  if (mScreen && mType != previousOrientation) {
+    // Use of mozorientationchange is deprecated.
+    rv = mScreen->DispatchTrustedEvent(NS_LITERAL_STRING("mozorientationchange"));
+    NS_WARNING_ASSERTION(NS_SUCCEEDED(rv), "DispatchTrustedEvent failed");
+  }
+
+  if (doc->Hidden() && !mVisibleListener) {
+    mVisibleListener = new VisibleEventListener();
+    rv = doc->AddSystemEventListener(NS_LITERAL_STRING("visibilitychange"),
+                                     mVisibleListener, /* useCapture = */ true);
+    NS_WARNING_ASSERTION(NS_SUCCEEDED(rv), "AddSystemEventListener failed");
+    return;
+  }
+
+  if (mType != doc->CurrentOrientationType()) {
+    doc->SetCurrentOrientation(mType, mAngle);
+
+    Promise* pendingPromise = doc->GetOrientationPendingPromise();
+    if (pendingPromise) {
+      pendingPromise->MaybeResolveWithUndefined();
+      doc->SetOrientationPendingPromise(nullptr);
+    }
+
+    nsCOMPtr<nsIRunnable> runnable = NewRunnableMethod(this,
+      &ScreenOrientation::DispatchChangeEvent);
+    rv = NS_DispatchToMainThread(runnable);
+    NS_WARNING_ASSERTION(NS_SUCCEEDED(rv), "NS_DispatchToMainThread failed");
+  }
+}
+
+void
+ScreenOrientation::UpdateActiveOrientationLock(ScreenOrientationInternal aOrientation)
+{
+  if (aOrientation == eScreenOrientation_None) {
+    hal::UnlockScreenOrientation();
+  } else {
+    DebugOnly<bool> ok = hal::LockScreenOrientation(aOrientation);
+    NS_WARNING_ASSERTION(ok, "hal::LockScreenOrientation failed");
+  }
+}
+
+void
+ScreenOrientation::DispatchChangeEvent()
+{
+  DebugOnly<nsresult> rv = DispatchTrustedEvent(NS_LITERAL_STRING("change"));
+  NS_WARNING_ASSERTION(NS_SUCCEEDED(rv), "DispatchTrustedEvent failed");
+}
+
+JSObject*
+ScreenOrientation::WrapObject(JSContext* aCx, JS::Handle<JSObject*> aGivenProto)
+{
+  return ScreenOrientationBinding::Wrap(aCx, this, aGivenProto);
+}
+
+bool
+ScreenOrientation::ShouldResistFingerprinting() const
+{
+  bool resist = false;
+  if (nsCOMPtr<nsPIDOMWindowInner> owner = GetOwner()) {
+    resist = nsContentUtils::ShouldResistFingerprinting(owner->GetDocShell());
+  }
+  return resist;
+}
+
+NS_IMPL_ISUPPORTS(ScreenOrientation::VisibleEventListener, nsIDOMEventListener)
+
+NS_IMETHODIMP
+ScreenOrientation::VisibleEventListener::HandleEvent(nsIDOMEvent* aEvent)
+{
+  // Document may have become visible, if the page is visible, run the steps
+  // following the "now visible algorithm" as specified.
+  nsCOMPtr<EventTarget> target = aEvent->InternalDOMEvent()->GetCurrentTarget();
+  MOZ_ASSERT(target);
+
+  nsCOMPtr<nsIDocument> doc = do_QueryInterface(target);
+  if (!doc || doc->Hidden()) {
+    return NS_OK;
+  }
+
+  auto* win = nsGlobalWindow::Cast(doc->GetInnerWindow());
+  if (!win) {
+    return NS_OK;
+  }
+
+  ErrorResult rv;
+  nsScreen* screen = win->GetScreen(rv);
+  if (NS_WARN_IF(rv.Failed())) {
+    return rv.StealNSResult();
+  }
+
+  MOZ_ASSERT(screen);
+  ScreenOrientation* orientation = screen->Orientation();
+  MOZ_ASSERT(orientation);
+
+  rv = target->RemoveSystemEventListener(NS_LITERAL_STRING("visibilitychange"),
+                                         this, true);
+  if (NS_WARN_IF(rv.Failed())) {
+    return rv.StealNSResult();
+  }
+
+  if (doc->CurrentOrientationType() != orientation->DeviceType()) {
+    doc->SetCurrentOrientation(orientation->DeviceType(), orientation->DeviceAngle());
+
+    Promise* pendingPromise = doc->GetOrientationPendingPromise();
+    if (pendingPromise) {
+      pendingPromise->MaybeResolveWithUndefined();
+      doc->SetOrientationPendingPromise(nullptr);
+    }
+
+    nsCOMPtr<nsIRunnable> runnable = NewRunnableMethod(orientation,
+      &ScreenOrientation::DispatchChangeEvent);
+    rv = NS_DispatchToMainThread(runnable);
+    if (NS_WARN_IF(rv.Failed())) {
+      return rv.StealNSResult();
+    }
+  }
+
+  return NS_OK;
+}
+
+NS_IMPL_ISUPPORTS(ScreenOrientation::FullScreenEventListener, nsIDOMEventListener)
+
+NS_IMETHODIMP
+ScreenOrientation::FullScreenEventListener::HandleEvent(nsIDOMEvent* aEvent)
+{
+#ifdef DEBUG
+  nsAutoString eventType;
+  aEvent->GetType(eventType);
+
+  MOZ_ASSERT(eventType.EqualsLiteral("fullscreenchange"));
+#endif
+
+  nsCOMPtr<EventTarget> target = aEvent->InternalDOMEvent()->GetCurrentTarget();
+  MOZ_ASSERT(target);
+
+  nsCOMPtr<nsIDocument> doc = do_QueryInterface(target);
+  MOZ_ASSERT(doc);
+
+  // We have to make sure that the event we got is the event sent when
+  // fullscreen is disabled because we could get one when fullscreen
+  // got enabled if the lock call is done at the same moment.
+  if (doc->Fullscreen()) {
+    return NS_OK;
+  }
+
+  hal::UnlockScreenOrientation();
+
+  nsresult rv = target->RemoveSystemEventListener(NS_LITERAL_STRING("fullscreenchange"),
+                                                  this, true);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  return NS_OK;
+}