Issue #1366 - Completely remove showModalDialog

38 files changed, 14 insertions, 1313 deletions

diff --git a/docshell/base/nsDocShell.cpp b/docshell/base/nsDocShell.cpp
index ebaf07bcd..6104ebfa7 100644
--- a/docshell/base/nsDocShell.cpp
+++ b/docshell/base/nsDocShell.cpp
@@ -13356,24 +13356,9 @@ nsDocShell::EnsureScriptEnvironment()
   uint32_t chromeFlags;
   browserChrome->GetChromeFlags(&chromeFlags);
 
-  bool isModalContentWindow =
-    (mItemType == typeContent) &&
-    (chromeFlags & nsIWebBrowserChrome::CHROME_MODAL_CONTENT_WINDOW);
-  // There can be various other content docshells associated with the
-  // top-level window, like sidebars. Make sure that we only create an
-  // nsGlobalModalWindow for the primary content shell.
-  if (isModalContentWindow) {
-    nsCOMPtr<nsIDocShellTreeItem> primaryItem;
-    nsresult rv =
-      mTreeOwner->GetPrimaryContentShell(getter_AddRefs(primaryItem));
-    NS_ENSURE_SUCCESS(rv, rv);
-    isModalContentWindow = (primaryItem == this);
-  }
-
   // If our window is modal and we're not opened as chrome, make
   // this window a modal content window.
-  mScriptGlobal =
-    NS_NewScriptGlobalObject(mItemType == typeChrome, isModalContentWindow);
+  mScriptGlobal = NS_NewScriptGlobalObject(mItemType == typeChrome);
   MOZ_ASSERT(mScriptGlobal);
 
   mScriptGlobal->SetDocShell(this);
diff --git a/dom/base/nsDeprecatedOperationList.h b/dom/base/nsDeprecatedOperationList.h
index ea4b05289..96a6c3ac0 100644
--- a/dom/base/nsDeprecatedOperationList.h
+++ b/dom/base/nsDeprecatedOperationList.h
@@ -34,7 +34,6 @@ DEPRECATED_OPERATION(UseOfCaptureEvents)
 DEPRECATED_OPERATION(UseOfReleaseEvents)
 DEPRECATED_OPERATION(UseOfDOM3LoadMethod)
 DEPRECATED_OPERATION(ChromeUseOfDOM3LoadMethod)
-DEPRECATED_OPERATION(ShowModalDialog)
 DEPRECATED_OPERATION(Window_Content)
 DEPRECATED_OPERATION(SyncXMLHttpRequest)
 DEPRECATED_OPERATION(DataContainerEvent)
diff --git a/dom/base/nsGlobalWindow.cpp b/dom/base/nsGlobalWindow.cpp
index 47b46dda0..0587eb892 100644
--- a/dom/base/nsGlobalWindow.cpp
+++ b/dom/base/nsGlobalWindow.cpp
@@ -909,7 +909,6 @@ nsPIDOMWindow<T>::nsPIDOMWindow(nsPIDOMWindowOuter *aOuterWindow)
   mMayHaveMouseEnterLeaveEventListener(false),
   mMayHavePointerEnterLeaveEventListener(false),
   mInnerObjectsFreed(false),
-  mIsModalContentWindow(false),
   mIsActive(false), mIsBackground(false),
   mMediaSuspend(Preferences::GetBool("media.block-autoplay-until-in-foreground", true) ?
     nsISuspendedTypes::SUSPENDED_BLOCK : nsISuspendedTypes::NONE_SUSPENDED),
@@ -1957,7 +1956,6 @@ nsGlobalWindow::CleanUp()
   }
 
   mArguments = nullptr;
-  mDialogArguments = nullptr;
 
   CleanupCachedXBLHandlers(this);
 
@@ -2195,7 +2193,6 @@ NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN_INTERNAL(nsGlobalWindow)
 
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mControllers)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mArguments)
-  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mDialogArguments)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mReturnValue)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mNavigator)
 
@@ -2274,7 +2271,6 @@ NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(nsGlobalWindow)
 
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mControllers)
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mArguments)
-  NS_IMPL_CYCLE_COLLECTION_UNLINK(mDialogArguments)
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mReturnValue)
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mNavigator)
 
@@ -3019,8 +3015,6 @@ nsGlobalWindow::SetNewDocument(nsIDocument* aDocument,
     } else {
       if (thisChrome) {
         newInnerWindow = nsGlobalChromeWindow::Create(this);
-      } else if (mIsModalContentWindow) {
-        newInnerWindow = nsGlobalModalWindow::Create(this);
       } else {
         newInnerWindow = nsGlobalWindow::Create(this);
       }
@@ -3871,31 +3865,16 @@ nsGlobalWindow::SetArguments(nsIArray *aArguments)
   MOZ_ASSERT(IsOuterWindow());
   nsresult rv;
 
-  // Historically, we've used the same machinery to handle openDialog arguments
-  // (exposed via window.arguments) and showModalDialog arguments (exposed via
-  // window.dialogArguments), even though the former is XUL-only and uses an XPCOM
-  // array while the latter is web-exposed and uses an arbitrary JS value.
-  // Moreover, per-spec |dialogArguments| is a property of the browsing context
-  // (outer), whereas |arguments| lives on the inner.
-  //
   // We've now mostly separated them, but the difference is still opaque to
   // nsWindowWatcher (the caller of SetArguments in this little back-and-forth
   // embedding waltz we do here).
   //
   // So we need to demultiplex the two cases here.
   nsGlobalWindow *currentInner = GetCurrentInnerWindowInternal();
-  if (mIsModalContentWindow) {
-    // nsWindowWatcher blindly converts the original nsISupports into an array
-    // of length 1. We need to recover it, and then cast it back to the concrete
-    // object we know it to be.
-    nsCOMPtr<nsISupports> supports = do_QueryElementAt(aArguments, 0, &rv);
-    NS_ENSURE_SUCCESS(rv, rv);
-    mDialogArguments = static_cast<DialogValueHolder*>(supports.get());
-  } else {
-    mArguments = aArguments;
-    rv = currentInner->DefineArgumentsProperty(aArguments);
-    NS_ENSURE_SUCCESS(rv, rv);
-  }
+
+  mArguments = aArguments;
+  rv = currentInner->DefineArgumentsProperty(aArguments);
+  NS_ENSURE_SUCCESS(rv, rv);
 
   return NS_OK;
 }
@@ -3904,7 +3883,6 @@ nsresult
 nsGlobalWindow::DefineArgumentsProperty(nsIArray *aArguments)
 {
   MOZ_ASSERT(IsInnerWindow());
-  MOZ_ASSERT(!mIsModalContentWindow); // Handled separately.
 
   nsIScriptContext *ctx = GetOuterWindowInternal()->mContext;
   NS_ENSURE_TRUE(aArguments && ctx, NS_ERROR_NOT_INITIALIZED);
@@ -5040,21 +5018,6 @@ nsGlobalWindow::IsPrivilegedChromeWindow(JSContext* aCx, JSObject* aObj)
          nsContentUtils::ObjectPrincipal(aObj) == nsContentUtils::GetSystemPrincipal();
 }
 
-/* static */ bool
-nsGlobalWindow::IsShowModalDialogEnabled(JSContext*, JSObject*)
-{
-  static bool sAddedPrefCache = false;
-  static bool sIsDisabled;
-  static const char sShowModalDialogPref[] = "dom.disable_window_showModalDialog";
-
-  if (!sAddedPrefCache) {
-    Preferences::AddBoolVarCache(&sIsDisabled, sShowModalDialogPref, false);
-    sAddedPrefCache = true;
-  }
-
-  return !sIsDisabled && !XRE_IsContentProcess();
-}
-
 nsIDOMOfflineResourceList*
 nsGlobalWindow::GetApplicationCache(ErrorResult& aError)
 {
@@ -9741,126 +9704,6 @@ nsGlobalWindow::ConvertDialogOptions(const nsAString& aOptions,
   }
 }
 
-already_AddRefed<nsIVariant>
-nsGlobalWindow::ShowModalDialogOuter(const nsAString& aUrl,
-                                     nsIVariant* aArgument,
-                                     const nsAString& aOptions,
-                                     nsIPrincipal& aSubjectPrincipal,
-                                     ErrorResult& aError)
-{
-  MOZ_RELEASE_ASSERT(IsOuterWindow());
-
-  if (mDoc) {
-    mDoc->WarnOnceAbout(nsIDocument::eShowModalDialog);
-  }
-
-  if (!IsShowModalDialogEnabled()) {
-    aError.Throw(NS_ERROR_NOT_AVAILABLE);
-    return nullptr;
-  }
-
-  RefPtr<DialogValueHolder> argHolder =
-    new DialogValueHolder(&aSubjectPrincipal, aArgument);
-
-  // Before bringing up the window/dialog, unsuppress painting and flush
-  // pending reflows.
-  EnsureReflowFlushAndPaint();
-
-  if (!AreDialogsEnabled()) {
-    // We probably want to keep throwing here; silently doing nothing is a bit
-    // weird given the typical use cases of showModalDialog().
-    aError.Throw(NS_ERROR_NOT_AVAILABLE);
-    return nullptr;
-  }
-
-  if (ShouldPromptToBlockDialogs() && !ConfirmDialogIfNeeded()) {
-    aError.Throw(NS_ERROR_NOT_AVAILABLE);
-    return nullptr;
-  }
-
-  nsCOMPtr<nsPIDOMWindowOuter> dlgWin;
-  nsAutoString options(NS_LITERAL_STRING("-moz-internal-modal=1,status=1"));
-
-  ConvertDialogOptions(aOptions, options);
-
-  options.AppendLiteral(",scrollbars=1,centerscreen=1,resizable=0");
-
-  EnterModalState();
-  uint32_t oldMicroTaskLevel = nsContentUtils::MicroTaskLevel();
-  nsContentUtils::SetMicroTaskLevel(0);
-  aError = OpenInternal(aUrl, EmptyString(), options,
-                        false,          // aDialog
-                        true,           // aContentModal
-                        true,           // aCalledNoScript
-                        true,           // aDoJSFixups
-                        true,           // aNavigate
-                        nullptr, argHolder, // args
-                        nullptr,        // aLoadInfo
-                        false,          // aForceNoOpener
-                        getter_AddRefs(dlgWin));
-  nsContentUtils::SetMicroTaskLevel(oldMicroTaskLevel);
-  LeaveModalState();
-  if (aError.Failed()) {
-    return nullptr;
-  }
-
-  nsCOMPtr<nsIDOMModalContentWindow> dialog = do_QueryInterface(dlgWin);
-  if (!dialog) {
-    return nullptr;
-  }
-
-  nsCOMPtr<nsIVariant> retVal;
-  aError = dialog->GetReturnValue(getter_AddRefs(retVal));
-  MOZ_ASSERT(!aError.Failed());
-
-  return retVal.forget();
-}
-
-already_AddRefed<nsIVariant>
-nsGlobalWindow::ShowModalDialog(const nsAString& aUrl, nsIVariant* aArgument,
-                                const nsAString& aOptions,
-                                nsIPrincipal& aSubjectPrincipal,
-                                ErrorResult& aError)
-{
-  FORWARD_TO_OUTER_OR_THROW(ShowModalDialogOuter,
-                            (aUrl, aArgument, aOptions, aSubjectPrincipal,
-                             aError), aError, nullptr);
-}
-
-void
-nsGlobalWindow::ShowModalDialog(JSContext* aCx, const nsAString& aUrl,
-                                JS::Handle<JS::Value> aArgument,
-                                const nsAString& aOptions,
-                                JS::MutableHandle<JS::Value> aRetval,
-                                nsIPrincipal& aSubjectPrincipal,
-                                ErrorResult& aError)
-{
-  MOZ_ASSERT(IsInnerWindow());
-
-  nsCOMPtr<nsIVariant> args;
-  aError = nsContentUtils::XPConnect()->JSToVariant(aCx,
-                                                    aArgument,
-                                                    getter_AddRefs(args));
-  if (aError.Failed()) {
-    return;
-  }
-
-  nsCOMPtr<nsIVariant> retVal =
-    ShowModalDialog(aUrl, args, aOptions, aSubjectPrincipal, aError);
-  if (aError.Failed()) {
-    return;
-  }
-
-  JS::Rooted<JS::Value> result(aCx);
-  if (retVal) {
-    aError = nsContentUtils::XPConnect()->VariantToJS(aCx,
-                                                      FastGetGlobalJSObject(),
-                                                      retVal, aRetval);
-  } else {
-    aRetval.setNull();
-  }
-}
-
 class ChildCommandDispatcher : public Runnable
 {
 public:
@@ -14613,174 +14456,6 @@ nsGlobalChromeWindow::TakeOpenerForInitialContentBrowser(mozIDOMWindowProxy** aO
   return NS_OK;
 }
 
-// nsGlobalModalWindow implementation
-
-// QueryInterface implementation for nsGlobalModalWindow
-NS_INTERFACE_MAP_BEGIN(nsGlobalModalWindow)
-  NS_INTERFACE_MAP_ENTRY(nsIDOMModalContentWindow)
-NS_INTERFACE_MAP_END_INHERITING(nsGlobalWindow)
-
-NS_IMPL_ADDREF_INHERITED(nsGlobalModalWindow, nsGlobalWindow)
-NS_IMPL_RELEASE_INHERITED(nsGlobalModalWindow, nsGlobalWindow)
-
-
-void
-nsGlobalWindow::GetDialogArgumentsOuter(JSContext* aCx,
-                                        JS::MutableHandle<JS::Value> aRetval,
-                                        nsIPrincipal& aSubjectPrincipal,
-                                        ErrorResult& aError)
-{
-  MOZ_RELEASE_ASSERT(IsOuterWindow());
-  MOZ_ASSERT(IsModalContentWindow(),
-             "This should only be called on modal windows!");
-
-  if (!mDialogArguments) {
-    MOZ_ASSERT(mIsClosed, "This window should be closed!");
-    aRetval.setUndefined();
-    return;
-  }
-
-  // This does an internal origin check, and returns undefined if the subject
-  // does not subsumes the origin of the arguments.
-  JS::Rooted<JSObject*> wrapper(aCx, GetWrapper());
-  JSAutoCompartment ac(aCx, wrapper);
-  mDialogArguments->Get(aCx, wrapper, &aSubjectPrincipal, aRetval, aError);
-}
-
-void
-nsGlobalWindow::GetDialogArguments(JSContext* aCx,
-                                   JS::MutableHandle<JS::Value> aRetval,
-                                   nsIPrincipal& aSubjectPrincipal,
-                                   ErrorResult& aError)
-{
-  FORWARD_TO_OUTER_OR_THROW(GetDialogArgumentsOuter,
-                            (aCx, aRetval, aSubjectPrincipal, aError),
-                            aError, );
-}
-
-/* static */ already_AddRefed<nsGlobalModalWindow>
-nsGlobalModalWindow::Create(nsGlobalWindow *aOuterWindow)
-{
-  RefPtr<nsGlobalModalWindow> window = new nsGlobalModalWindow(aOuterWindow);
-  window->InitWasOffline();
-  return window.forget();
-}
-
-NS_IMETHODIMP
-nsGlobalModalWindow::GetDialogArguments(nsIVariant **aArguments)
-{
-  FORWARD_TO_OUTER_MODAL_CONTENT_WINDOW(GetDialogArguments, (aArguments),
-                                        NS_ERROR_NOT_INITIALIZED);
-
-  // This does an internal origin check, and returns undefined if the subject
-  // does not subsumes the origin of the arguments.
-  return mDialogArguments->Get(nsContentUtils::SubjectPrincipal(), aArguments);
-}
-
-/* static */ already_AddRefed<nsGlobalWindow>
-nsGlobalWindow::Create(nsGlobalWindow *aOuterWindow)
-{
-  RefPtr<nsGlobalWindow> window = new nsGlobalWindow(aOuterWindow);
-  window->InitWasOffline();
-  return window.forget();
-}
-
-void
-nsGlobalWindow::InitWasOffline()
-{
-  mWasOffline = NS_IsOffline();
-}
-
-void
-nsGlobalWindow::GetReturnValueOuter(JSContext* aCx,
-                                    JS::MutableHandle<JS::Value> aReturnValue,
-                                    nsIPrincipal& aSubjectPrincipal,
-                                    ErrorResult& aError)
-{
-  MOZ_RELEASE_ASSERT(IsOuterWindow());
-  MOZ_ASSERT(IsModalContentWindow(),
-             "This should only be called on modal windows!");
-
-  if (mReturnValue) {
-    JS::Rooted<JSObject*> wrapper(aCx, GetWrapper());
-    JSAutoCompartment ac(aCx, wrapper);
-    mReturnValue->Get(aCx, wrapper, &aSubjectPrincipal, aReturnValue, aError);
-  } else {
-    aReturnValue.setUndefined();
-  }
-}
-
-void
-nsGlobalWindow::GetReturnValue(JSContext* aCx,
-                               JS::MutableHandle<JS::Value> aReturnValue,
-                               nsIPrincipal& aSubjectPrincipal,
-                               ErrorResult& aError)
-{
-  FORWARD_TO_OUTER_OR_THROW(GetReturnValueOuter,
-                            (aCx, aReturnValue, aSubjectPrincipal, aError),
-                            aError, );
-}
-
-NS_IMETHODIMP
-nsGlobalModalWindow::GetReturnValue(nsIVariant **aRetVal)
-{
-  FORWARD_TO_OUTER_MODAL_CONTENT_WINDOW(GetReturnValue, (aRetVal), NS_OK);
-
-  if (!mReturnValue) {
-    nsCOMPtr<nsIVariant> variant = CreateVoidVariant();
-    variant.forget(aRetVal);
-    return NS_OK;
-  }
-  return mReturnValue->Get(nsContentUtils::SubjectPrincipal(), aRetVal);
-}
-
-void
-nsGlobalWindow::SetReturnValueOuter(JSContext* aCx,
-                                    JS::Handle<JS::Value> aReturnValue,
-                                    nsIPrincipal& aSubjectPrincipal,
-                                    ErrorResult& aError)
-{
-  MOZ_RELEASE_ASSERT(IsOuterWindow());
-  MOZ_ASSERT(IsModalContentWindow(),
-             "This should only be called on modal windows!");
-
-  nsCOMPtr<nsIVariant> returnValue;
-  aError =
-    nsContentUtils::XPConnect()->JSToVariant(aCx, aReturnValue,
-                                             getter_AddRefs(returnValue));
-  if (!aError.Failed()) {
-    mReturnValue = new DialogValueHolder(&aSubjectPrincipal, returnValue);
-  }
-}
-
-void
-nsGlobalWindow::SetReturnValue(JSContext* aCx,
-                               JS::Handle<JS::Value> aReturnValue,
-                               nsIPrincipal& aSubjectPrincipal,
-                               ErrorResult& aError)
-{
-  FORWARD_TO_OUTER_OR_THROW(SetReturnValueOuter,
-                            (aCx, aReturnValue, aSubjectPrincipal, aError),
-                            aError, );
-}
-
-NS_IMETHODIMP
-nsGlobalModalWindow::SetReturnValue(nsIVariant *aRetVal)
-{
-  FORWARD_TO_OUTER_MODAL_CONTENT_WINDOW(SetReturnValue, (aRetVal), NS_OK);
-
-  mReturnValue = new DialogValueHolder(nsContentUtils::SubjectPrincipal(),
-                                       aRetVal);
-  return NS_OK;
-}
-
-/* static */
-bool
-nsGlobalWindow::IsModalContentWindow(JSContext* aCx, JSObject* aGlobal)
-{
-  return xpc::WindowOrNull(aGlobal)->IsModalContentWindow();
-}
-
 #if defined(MOZ_WIDGET_ANDROID)
 int16_t
 nsGlobalWindow::Orientation(CallerType aCallerType) const
diff --git a/dom/base/nsGlobalWindow.h b/dom/base/nsGlobalWindow.h
index 1f420895c..5cfd3f056 100644
--- a/dom/base/nsGlobalWindow.h
+++ b/dom/base/nsGlobalWindow.h
@@ -458,9 +458,6 @@ public:
 
   static bool IsPrivilegedChromeWindow(JSContext* /* unused */, JSObject* aObj);
 
-  static bool IsShowModalDialogEnabled(JSContext* /* unused */ = nullptr,
-                                       JSObject* /* unused */ = nullptr);
-
   bool DoResolve(JSContext* aCx, JS::Handle<JSObject*> aObj,
                  JS::Handle<jsid> aId,
                  JS::MutableHandle<JS::PropertyDescriptor> aDesc);
@@ -583,9 +580,6 @@ public:
     return mIsChrome;
   }
 
-  using nsPIDOMWindow::IsModalContentWindow;
-  static bool IsModalContentWindow(JSContext* aCx, JSObject* aGlobal);
-
   // GetScrollFrame does not flush.  Callers should do it themselves as needed,
   // depending on which info they actually want off the scrollable frame.
   nsIScrollableFrame *GetScrollFrame();
@@ -950,12 +944,6 @@ public:
                                                 mozilla::ErrorResult& aRv);
   void PrintOuter(mozilla::ErrorResult& aError);
   void Print(mozilla::ErrorResult& aError);
-  void ShowModalDialog(JSContext* aCx, const nsAString& aUrl,
-                       JS::Handle<JS::Value> aArgument,
-                       const nsAString& aOptions,
-                       JS::MutableHandle<JS::Value> aRetval,
-                       nsIPrincipal& aSubjectPrincipal,
-                       mozilla::ErrorResult& aError);
   void PostMessageMoz(JSContext* aCx, JS::Handle<JS::Value> aMessage,
                       const nsAString& aTargetOrigin,
                       const mozilla::dom::Optional<mozilla::dom::Sequence<JS::Value > >& aTransfer,
@@ -1227,12 +1215,6 @@ public:
                        mozilla::dom::Element* aPanel,
                        mozilla::ErrorResult& aError);
 
-  void GetDialogArgumentsOuter(JSContext* aCx, JS::MutableHandle<JS::Value> aRetval,
-                               nsIPrincipal& aSubjectPrincipal,
-                               mozilla::ErrorResult& aError);
-  void GetDialogArguments(JSContext* aCx, JS::MutableHandle<JS::Value> aRetval,
-                          nsIPrincipal& aSubjectPrincipal,
-                          mozilla::ErrorResult& aError);
   void GetReturnValueOuter(JSContext* aCx, JS::MutableHandle<JS::Value> aReturnValue,
                            nsIPrincipal& aSubjectPrincipal,
                            mozilla::ErrorResult& aError);
@@ -1681,18 +1663,6 @@ protected:
                       nsIPrincipal& aSubjectPrincipal,
                       mozilla::ErrorResult& aError);
 
-  already_AddRefed<nsIVariant>
-    ShowModalDialogOuter(const nsAString& aUrl, nsIVariant* aArgument,
-                         const nsAString& aOptions,
-                         nsIPrincipal& aSubjectPrincipal,
-                         mozilla::ErrorResult& aError);
-
-  already_AddRefed<nsIVariant>
-    ShowModalDialog(const nsAString& aUrl, nsIVariant* aArgument,
-                    const nsAString& aOptions,
-                    nsIPrincipal& aSubjectPrincipal,
-                    mozilla::ErrorResult& aError);
-
   // Ask the user if further dialogs should be blocked, if dialogs are currently
   // being abused. This is used in the cases where we have no modifiable UI to
   // show, in that case we show a separate dialog to ask this question.
@@ -1832,9 +1802,6 @@ protected:
   // For |window.arguments|, via |openDialog|.
   nsCOMPtr<nsIArray>            mArguments;
 
-  // For |window.dialogArguments|, via |showModalDialog|.
-  RefPtr<DialogValueHolder> mDialogArguments;
-
   // Only used in the outer.
   RefPtr<DialogValueHolder> mReturnValue;
 
@@ -2067,40 +2034,14 @@ public:
   nsCOMPtr<mozIDOMWindowProxy> mOpenerForInitialContentBrowser;
 };
 
-/*
- * nsGlobalModalWindow inherits from nsGlobalWindow. It is the global
- * object created for a modal content windows only (i.e. not modal
- * chrome dialogs).
- */
-class nsGlobalModalWindow : public nsGlobalWindow,
-                            public nsIDOMModalContentWindow
-{
-public:
-  NS_DECL_ISUPPORTS_INHERITED
-  NS_DECL_NSIDOMMODALCONTENTWINDOW
-
-  static already_AddRefed<nsGlobalModalWindow> Create(nsGlobalWindow *aOuterWindow);
-
-protected:
-  explicit nsGlobalModalWindow(nsGlobalWindow *aOuterWindow)
-    : nsGlobalWindow(aOuterWindow)
-  {
-    mIsModalContentWindow = true;
-  }
-
-  ~nsGlobalModalWindow() {}
-};
-
 /* factory function */
 inline already_AddRefed<nsGlobalWindow>
-NS_NewScriptGlobalObject(bool aIsChrome, bool aIsModalContentWindow)
+NS_NewScriptGlobalObject(bool aIsChrome)
 {
   RefPtr<nsGlobalWindow> global;
 
   if (aIsChrome) {
     global = nsGlobalChromeWindow::Create(nullptr);
-  } else if (aIsModalContentWindow) {
-    global = nsGlobalModalWindow::Create(nullptr);
   } else {
     global = nsGlobalWindow::Create(nullptr);
   }
diff --git a/dom/base/nsPIDOMWindow.h b/dom/base/nsPIDOMWindow.h
index 47affbb06..5c07bf4d4 100644
--- a/dom/base/nsPIDOMWindow.h
+++ b/dom/base/nsPIDOMWindow.h
@@ -303,11 +303,6 @@ public:
   virtual bool CanClose() = 0;
   virtual void ForceClose() = 0;
 
-  bool IsModalContentWindow() const
-  {
-    return mIsModalContentWindow;
-  }
-
   /**
    * Call this to indicate that some node (this window, its document,
    * or content in that document) has a paint event listener.
@@ -629,11 +624,6 @@ protected:
   // This member is only used by inner windows.
   bool                   mInnerObjectsFreed;
 
-
-  // This variable is used on both inner and outer windows (and they
-  // should match).
-  bool                   mIsModalContentWindow;
-
   // Tracks activation state that's used for :-moz-window-inactive.
   // Only used on outer windows.
   bool                   mIsActive;
diff --git a/dom/base/nsSandboxFlags.h b/dom/base/nsSandboxFlags.h
index d18527597..b8c9ac357 100644
--- a/dom/base/nsSandboxFlags.h
+++ b/dom/base/nsSandboxFlags.h
@@ -29,8 +29,7 @@ const unsigned long SANDBOXED_NAVIGATION  = 0x1;
 
 /**
  * This flag prevents content from creating new auxiliary browsing contexts,
- * e.g. using the target attribute, the window.open() method, or the
- * showModalDialog() method.
+ * e.g. using the target attribute, or the window.open() method.
  */
 const unsigned long SANDBOXED_AUXILIARY_NAVIGATION = 0x2;
 
diff --git a/dom/base/test/mochitest.ini b/dom/base/test/mochitest.ini
index b3b804ce4..3dfd666f8 100644
--- a/dom/base/test/mochitest.ini
+++ b/dom/base/test/mochitest.ini
@@ -196,7 +196,6 @@ support-files =
   formReset.html
   invalid_accesscontrol.resource
   invalid_accesscontrol.resource^headers^
-  mutationobserver_dialog.html
   orientationcommon.js
   script-1_bug597345.sjs
   script-2_bug597345.js
@@ -627,9 +626,6 @@ subsuite = clipboard
 skip-if = toolkit == 'android' #bug 904183
 [test_createHTMLDocument.html]
 [test_declare_stylesheet_obsolete.html]
-[test_dialogArguments.html]
-tags = openwindow
-skip-if = toolkit == 'android' || e10s # showmodaldialog
 [test_document.all_iteration.html]
 [test_document.all_unqualified.html]
 [test_document_constructor.html]
diff --git a/dom/base/test/mutationobserver_dialog.html b/dom/base/test/mutationobserver_dialog.html
deleted file mode 100644
index 2cc815309..000000000
--- a/dom/base/test/mutationobserver_dialog.html
+++ /dev/null
@@ -1,62 +0,0 @@
-<html>
-  <head>
-    <title></title>
-    <script>
-
-    var div = document.createElement("div");
-
-    var M;
-    if ("MozMutationObserver" in window) {
-      M = window.MozMutationObserver;
-    } else if ("WebKitMutationObserver" in window) {
-      M = window.WebKitMutationObserver;
-    } else {
-      M = window.MutationObserver;
-    }
-
-    var didCall1 = false;
-    var didCall2 = false;
-    function testMutationObserverInDialog() {
-      div.innerHTML = "<span>1</span><span>2</span>";
-      m = new M(function(records, observer) {
-          opener.is(records[0].type, "childList", "Should have got childList");
-          opener.is(records[0].removedNodes.length, 2, "Should have got removedNodes");
-          opener.is(records[0].addedNodes.length, 1, "Should have got addedNodes");
-          observer.disconnect();
-          m = null;
-          didCall1 = true;
-        });
-      m.observe(div, { childList: true });
-      div.innerHTML = "<span><span>foo</span></span>";
-    }
-
-    function testMutationObserverInDialog2() {
-      div.innerHTML = "<span>1</span><span>2</span>";
-      m = new M(function(records, observer) {
-          opener.is(records[0].type, "childList", "Should have got childList");
-          opener.is(records[0].removedNodes.length, 2, "Should have got removedNodes");
-          opener.is(records[0].addedNodes.length, 1, "Should have got addedNodes");
-          observer.disconnect();
-          m = null;
-          didCall2 = true;
-        });
-      m.observe(div, { childList: true });
-      div.innerHTML = "<span><span>foo</span></span>";
-    }
-
-    window.addEventListener("load", testMutationObserverInDialog);
-    window.addEventListener("load", testMutationObserverInDialog2);
-    window.addEventListener("load",
-      function() {
-        opener.ok(didCall1, "Should have called 1st mutation callback");
-        opener.ok(didCall2, "Should have called 2nd mutation callback");
-        window.close();
-      });
-    </script>
-    <style>
-    </style>
-  </head>
-  <body>
-    <input type="button" onclick="window.close()" value="close">
-  </body>
-</html>
diff --git a/dom/base/test/test_dialogArguments.html b/dom/base/test/test_dialogArguments.html
deleted file mode 100644
index 70a091d00..000000000
--- a/dom/base/test/test_dialogArguments.html
+++ /dev/null
@@ -1,31 +0,0 @@
-<!DOCTYPE html>
-<html>
-<head>
-	<title>Test for Bug 1019761</title>
-	<script type="application/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
-	<link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
-
-	<meta http-equiv="content-type" content="text/html; charset=utf-8">
-</head>
-<body>
-<script type="application/javascript">
-
-/*
-	Tests whether Firefox crashes when accessing the dialogArguments property
-	of a modal window that has been closed.
-*/
-SimpleTest.waitForExplicitFinish();
-
-function openModal() {
-	showModalDialog("javascript:opener.winRef = window; \
-		window.opener.setTimeout(\'winRef.dialogArguments;\', 0);\
-		window.close();");
-
-	ok(true, "dialogArguments did not cause a crash.");
-	SimpleTest.finish();
-}
-
-window.onload = openModal;
-</script>
-</body>
-</html>
diff --git a/dom/base/test/test_mutationobservers.html b/dom/base/test/test_mutationobservers.html
index bde07c79c..a6de89595 100644
--- a/dom/base/test/test_mutationobservers.html
+++ b/dom/base/test/test_mutationobservers.html
@@ -484,28 +484,6 @@ function testSyncXHR() {
 
 function testSyncXHR2() {
   ok(callbackHandled, "Should have called the mutation callback!");
-  then(testModalDialog);
-}
-
-function testModalDialog() {
-  var didHandleCallback = false;
-  div.innerHTML = "<span>1</span><span>2</span>";
-  m = new M(function(records, observer) {
-      is(records[0].type, "childList", "Should have got childList");
-      is(records[0].removedNodes.length, 2, "Should have got removedNodes");
-      is(records[0].addedNodes.length, 1, "Should have got addedNodes");
-      observer.disconnect();
-      m = null;
-      didHandleCallback = true;
-    });
-  m.observe(div, { childList: true });
-  div.innerHTML = "<span><span>foo</span></span>";
-  try {
-    window.showModalDialog("mutationobserver_dialog.html");
-    ok(didHandleCallback, "Should have called the callback while showing modal dialog!");
-  } catch(e) {
-    todo(false, "showModalDialog not implemented on this platform");
-  }
   then(testTakeRecords);
 }
 
diff --git a/dom/html/test/file_iframe_sandbox_c_if4.html b/dom/html/test/file_iframe_sandbox_c_if4.html
index 53bf49559..828592d63 100644
--- a/dom/html/test/file_iframe_sandbox_c_if4.html
+++ b/dom/html/test/file_iframe_sandbox_c_if4.html
@@ -12,7 +12,7 @@
   }
 
   function doStuff() {
-    // try to open a new window via target="_blank", target="BC341604", window.open(), and showModalDialog()
+    // try to open a new window via target="_blank", target="BC341604", and window.open()
     // the window we try to open closes itself once it opens
     sendMouseEvent({type:'click'}, 'target_blank');
     sendMouseEvent({type:'click'}, 'target_BC341604');
@@ -25,15 +25,6 @@
     }
 
     ok(threw, "window.open threw a JS exception and was not allowed");
-
-    threw = false;
-    try {
-      window.showModalDialog("about:blank");
-    } catch(error) {
-      threw = true;
-    }
-
-    ok(threw, "window.showModalDialog threw a JS exception and was not allowed");
   }
 </script>
 <body onLoad="doStuff()">
diff --git a/dom/html/test/file_iframe_sandbox_j_if1.html b/dom/html/test/file_iframe_sandbox_j_if1.html
deleted file mode 100644
index 6d4347dfc..000000000
--- a/dom/html/test/file_iframe_sandbox_j_if1.html
+++ /dev/null
@@ -1,30 +0,0 @@
-<!DOCTYPE HTML>
-<html>
-<head>
-  <meta charset="utf-8">
-  <title>Test for Bug 766282</title>
-  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
-</head>
-
-<script type="text/javascript">
-  function doStuff() {
-    // Open a new window via showModalDialog().
-    try {
-      window.showModalDialog("file_iframe_sandbox_k_if5.html");
-    } catch(e) {
-      window.parent.ok_wrapper(false, "iframes sandboxed with allow-popups and allow-modals should be able to open a modal dialog");
-    }
-
-    // Open a new window via showModalDialog().
-    try {
-      window.showModalDialog("file_iframe_sandbox_k_if7.html");
-    } catch(e) {
-      window.parent.ok_wrapper(false, "iframes sandboxed with allow-popups and allow-modals should be able to open a modal dialog");
-    }
-  }
-</script>
-
-<body onLoad="doStuff()">
-  I am sandboxed with "allow-scripts allow-popups allow-same-origin allow-forms allow-top-navigation".
-</body>
-</html>
diff --git a/dom/html/test/file_iframe_sandbox_j_if2.html b/dom/html/test/file_iframe_sandbox_j_if2.html
deleted file mode 100644
index 9552307ee..000000000
--- a/dom/html/test/file_iframe_sandbox_j_if2.html
+++ /dev/null
@@ -1,28 +0,0 @@
-<!DOCTYPE HTML>
-<html>
-<head>
-  <meta charset="utf-8">
-  <title>Test for Bug 766282</title>
-  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
-</head>
-
-<script type="text/javascript">
-  function doSubOpens() {
-    // Open a new window showModalDialog().
-    try {
-      window.showModalDialog("file_iframe_sandbox_k_if9.html");
-    } catch(e) {
-      window.parent.ok_wrapper(false, "iframes sandboxed with allow-popups and allow-modals should be able to open a modal dialog");
-    }
-  }
-
-  window.doSubOpens = doSubOpens;
-</script>
-
-<body>
-  I am sandboxed but with "allow-scripts allow-popups allow-same-origin".
-  After my initial load, "allow-same-origin" is removed and then I open file_iframe_sandbox_k_if9.html,
-  which attemps to call a function in my parent.
-  This should succeed since the new sandbox flags shouldn't have taken affect on me until I'm reloaded.
-</body>
-</html>
diff --git a/dom/html/test/file_iframe_sandbox_j_if3.html b/dom/html/test/file_iframe_sandbox_j_if3.html
deleted file mode 100644
index 07c5b66c1..000000000
--- a/dom/html/test/file_iframe_sandbox_j_if3.html
+++ /dev/null
@@ -1,27 +0,0 @@
-<!DOCTYPE HTML>
-<html>
-<head>
-  <meta charset="utf-8">
-  <title>Tests for Bug 766282</title>
-  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
-
-</head>
-<script type="text/javascript">
-  function ok(result, desc) {
-    window.parent.ok_wrapper(result, desc);
-  }
-
-  function doStuff() {
-    // Try to open a new window via showModalDialog().
-    // The window we try to open closes itself once it opens.
-    try {
-      window.showModalDialog("file_iframe_sandbox_open_window_pass.html");
-    } catch(e) {
-      ok(false, "iframes sandboxed with allow-popups and allow-modals should be able to open a modal dialog");
-    }
-  }
-</script>
-<body onLoad="doStuff()">
-  I am sandboxed but with "allow-popups allow-scripts allow-same-origin"
-</body>
-</html>
diff --git a/dom/html/test/mochitest.ini b/dom/html/test/mochitest.ini
index 024de1cd9..4a50a9c3f 100644
--- a/dom/html/test/mochitest.ini
+++ b/dom/html/test/mochitest.ini
@@ -154,9 +154,6 @@ support-files =
   file_iframe_sandbox_form_pass.html
   file_iframe_sandbox_g_if1.html
   file_iframe_sandbox_h_if1.html
-  file_iframe_sandbox_j_if1.html
-  file_iframe_sandbox_j_if2.html
-  file_iframe_sandbox_j_if3.html
   file_iframe_sandbox_k_if1.html
   file_iframe_sandbox_k_if2.html
   file_iframe_sandbox_k_if3.html
@@ -471,9 +468,6 @@ skip-if = toolkit == 'android' # just copy the conditions from the test above
 tags = openwindow
 [test_iframe_sandbox_inheritance.html]
 tags = openwindow
-[test_iframe_sandbox_modal.html]
-tags = openwindow
-skip-if = toolkit == 'android' || e10s #modal tests fail on android
 [test_iframe_sandbox_navigation.html]
 tags = openwindow
 [test_iframe_sandbox_navigation2.html]
@@ -540,8 +534,6 @@ skip-if = toolkit == 'android' #bug 811644
 [test_bug369370.html]
 skip-if = toolkit == "android" || toolkit == "windows" # disabled on Windows because of bug 1234520
 [test_bug380383.html]
-[test_bug391777.html]
-skip-if = toolkit == 'android' || e10s
 [test_bug402680.html]
 [test_bug403868.html]
 [test_bug403868.xhtml]
@@ -607,4 +599,4 @@ skip-if = os == "android" # up/down arrow keys not supported on android
 [test_script_module.html]
 support-files =
   file_script_module.html
-  file_script_nomodule.html
\ No newline at end of file
+  file_script_nomodule.html
diff --git a/dom/html/test/test_bug391777.html b/dom/html/test/test_bug391777.html
deleted file mode 100644
index aa01a45de..000000000
--- a/dom/html/test/test_bug391777.html
+++ /dev/null
@@ -1,25 +0,0 @@
-<!DOCTYPE HTML>
-<html>
-<!--
-https://bugzilla.mozilla.org/show_bug.cgi?id=391777
--->
-<head>
-  <title>Test for Bug 391777</title>
-  <script type="text/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>        
-  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
-</head>
-<body>
-<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=391777">Mozilla Bug 391777</a>
-<p id="display"></p>
-<script class="testbody" type="text/javascript">
-
-/** Test for Bug 391777 **/
-var arg = {};
-arg.testVal = "foo";
-var result = window.showModalDialog("javascript:window.returnValue = window.dialogArguments.testVal; window.close(); 'This window should close on its own.';", arg);
-ok(true, "We should get here without user interaction");
-is(result, "foo", "Unexpected result from showModalDialog");
-
-</script>
-</body>
-</html>
diff --git a/dom/html/test/test_iframe_sandbox_general.html b/dom/html/test/test_iframe_sandbox_general.html
index 6d3a190ee..83f0e9045 100644
--- a/dom/html/test/test_iframe_sandbox_general.html
+++ b/dom/html/test/test_iframe_sandbox_general.html
@@ -41,7 +41,7 @@ function ok_wrapper(result, desc) {
     passedTests++;
   }
 
-  if (completedTests == 33) {
+  if (completedTests == 32) {
     is(passedTests, completedTests, "There are " + completedTests + " general tests that should pass");
     SimpleTest.finish();
   }
diff --git a/dom/html/test/test_iframe_sandbox_modal.html b/dom/html/test/test_iframe_sandbox_modal.html
deleted file mode 100644
index 1307ea9a5..000000000
--- a/dom/html/test/test_iframe_sandbox_modal.html
+++ /dev/null
@@ -1,122 +0,0 @@
-<!DOCTYPE HTML>
-<html>
-<!--
-https://bugzilla.mozilla.org/show_bug.cgi?id=766282
-implement allow-popups directive for iframe sandbox
--->
-<head>
-  <meta charset="utf-8">
-  <title>Tests for Bug 766282</title>
-  <script type="application/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
-  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
-</head>
-
-<script>
-
-SimpleTest.waitForExplicitFinish();
-SimpleTest.requestFlakyTimeout("untriaged");
-
-// A postMessage handler that is used by sandboxed iframes without
-// 'allow-same-origin' to communicate pass/fail back to this main page.
-window.addEventListener("message", receiveMessage, false);
-
-function receiveMessage(event) {
-  switch (event.data.type) {
-    case "attempted":
-      testAttempted();
-      break;
-    case "ok":
-      ok_wrapper(event.data.ok, event.data.desc, event.data.addToAttempted);
-      break;
-    default:
-      // allow for old style message
-      if (event.data.ok != undefined) {
-        ok_wrapper(event.data.ok, event.data.desc, event.data.addToAttempted);
-      }
-  }
-}
-
-var attemptedTests = 0;
-var passedTests = 0;
-var totalTestsToPass = 5;
-var totalTestsToAttempt = 5;
-
-function ok_wrapper(result, desc, addToAttempted = true) {
-  ok(result, desc);
-
-  if (result) {
-    passedTests++;
-  }
-
-  if (addToAttempted) {
-    testAttempted();
-  }
-}
-
-// Added so that tests that don't register unless they fail,
-// can at least notify that they've attempted to run.
-function testAttempted() {
-  attemptedTests++;
-  if (attemptedTests == totalTestsToAttempt) {
-    // Make sure all tests have had a chance to complete.
-    setTimeout(function() {finish();}, 1000);
-  }
-}
-
-var finishCalled = false;
-
-function finish() {
-  if (!finishCalled) {
-    finishCalled = true;
-    is(passedTests, totalTestsToPass, "There are " + totalTestsToPass + " modal tests that should pass");
-
-    SimpleTest.finish();
-  }
-}
-
-function doTest() {
-  // passes if good and fails if bad
-  // 1) A window opened from inside an iframe that has sandbox = "allow-scripts allow-popups
-  // allow-same-origin" should not have its origin sandbox flag set and be able to access
-  // document.cookie. (Done by file_iframe_sandbox_k_if5.html opened from
-  // file_iframe_sandbox_j_if1.html) using showModalDialog.)
-
-  // passes if good
-  // 2) A window opened from inside an iframe that has sandbox = "allow-scripts allow-popups
-  // allow-top-navigation" should not have its top-level navigation sandbox flag set and be able to
-  // navigate top. (Done by file_iframe_sandbox_k_if5.html (and if6) opened from
-  // file_iframe_sandbox_j_if1.html) using showModalDialog.)
-
-  // passes if good
-  // 3) A window opened from inside an iframe that has sandbox = "allow-scripts allow-popups
-  // all-forms" should not have its forms sandbox flag set and be able to submit forms.
-  // (Done by file_iframe_sandbox_k_if7.html opened from
-  // file_iframe_sandbox_j_if1.html) using showModalDialog.)
-
-  // passes if good
-  // 4) Make sure that the sandbox flags copied to a new browsing context are taken from the
-  // current active document not the browsing context (iframe / docShell).
-  // This is done by removing allow-same-origin and calling doSubOpens from file_iframe_sandbox_j_if2.html,
-  // which opens file_iframe_sandbox_k_if9.html using showModalDialog.
-  var if_2 = document.getElementById('if_2');
-  if_2.sandbox = 'allow-scripts allow-popups';
-  if_2.contentWindow.doSubOpens();
-
-  // passes if good
-  // 5) Test that a sandboxed iframe with "allow-popups" can open a new window using window.ShowModalDialog.
-  // This is done via file_iframe_sandbox_j_if3.html which is sandboxed with "allow-popups allow-scripts
-  // allow-same-origin". The window it attempts to open calls window.opener.ok(true, ...) and
-  // file_iframe_j_if3.html has an ok() function that calls window.parent.ok_wrapper.
-}
-
-addLoadEvent(doTest);
-</script>
-
-<body>
-<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=766282">Mozilla Bug 766282</a> - implement allow-popups directive for iframe sandbox
-<p id="display"></p>
-<div id="content">
-<iframe sandbox="allow-scripts allow-popups allow-modals allow-same-origin allow-forms allow-top-navigation" id="if_1" src="file_iframe_sandbox_j_if1.html" height="10" width="10"></iframe>
-<iframe sandbox="allow-scripts allow-popups allow-modals allow-same-origin" id="if_2" src="file_iframe_sandbox_j_if2.html" height="10" width="10"></iframe>
-<iframe sandbox="allow-popups allow-modals allow-same-origin allow-scripts" id="if_3" src="file_iframe_sandbox_j_if3.html" height="10" width="10"></iframe>
-</div>
diff --git a/dom/locales/en-US/chrome/dom/dom.properties b/dom/locales/en-US/chrome/dom/dom.properties
index 0472979d7..6bd3aac94 100644
--- a/dom/locales/en-US/chrome/dom/dom.properties
+++ b/dom/locales/en-US/chrome/dom/dom.properties
@@ -174,8 +174,6 @@ UseOfCaptureEventsWarning=Use of captureEvents() is deprecated. To upgrade your
 UseOfReleaseEventsWarning=Use of releaseEvents() is deprecated. To upgrade your code, use the DOM 2 removeEventListener() method. For more help http://developer.mozilla.org/en/docs/DOM:element.removeEventListener
 # LOCALIZATION NOTE: Do not translate "document.load()" or "XMLHttpRequest"
 UseOfDOM3LoadMethodWarning=Use of document.load() is deprecated. To upgrade your code, use the DOM XMLHttpRequest object. For more help https://developer.mozilla.org/en/XMLHttpRequest
-# LOCALIZATION NOTE: Do not translate "window.showModalDialog()" or "window.open()"
-ShowModalDialogWarning=Use of window.showModalDialog() is deprecated. Use window.open() instead. For more help https://developer.mozilla.org/en-US/docs/Web/API/Window.open
 # LOCALIZATION NOTE: Do not translate "window._content" or "window.content"
 Window_ContentWarning=window._content is deprecated.  Please use window.content instead.
 # LOCALIZATION NOTE: Do not translate "XMLHttpRequest"
diff --git a/dom/media/webspeech/recognition/test/test_nested_eventloop.html b/dom/media/webspeech/recognition/test/test_nested_eventloop.html
index bdbed6524..8b4cea6d7 100644
--- a/dom/media/webspeech/recognition/test/test_nested_eventloop.html
+++ b/dom/media/webspeech/recognition/test/test_nested_eventloop.html
@@ -21,7 +21,7 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=650295
   SimpleTest.waitForExplicitFinish();
 
   /*
-   * window.showModalDialog() can be used to spin the event loop, causing
+   * SpecialPowers.spinEventLoop can be used to spin the event loop, causing
    * queued SpeechEvents (such as those created by calls to start(), stop()
    * or abort()) to be processed immediately.
    * When this is done from inside DOM event handlers, it is possible to
@@ -33,7 +33,7 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=650295
   }
   function doneFunc() {
     // Trigger gc now and wait some time to make sure this test gets the blame
-    // for any assertions caused by showModalDialog
+    // for any assertions caused by spinning the event loop.
     //
     // NB - The assertions should be gone, but this looks too scary to touch
     // during batch cleanup.
diff --git a/dom/tests/mochitest/bugs/file_bug291653.html b/dom/tests/mochitest/bugs/file_bug291653.html
deleted file mode 100644
index 4bfc8337e..000000000
--- a/dom/tests/mochitest/bugs/file_bug291653.html
+++ /dev/null
@@ -1,28 +0,0 @@
-<html>
-  <head>
-    <script>
-    <!--
-    function listener1() {
-      window.showModalDialog("data:text/html,<script>var maintest = opener.opener; opener.location = 'data:text/html,test'; maintest.end(); window.close();</script>");
-    }
-
-    function listener2() {
-      opener.secondListenerDidRun = true;
-    }
-    
-    window.addEventListener("foo", listener1);
-    window.addEventListener("foo", listener2);
-    
-    
-    function fireFoo() {
-      var e = document.createEvent("Events");
-      e.initEvent("foo", true, true);
-      window.dispatchEvent(e);
-    }
-    //-->
-    </script>
-  </head>
-  <body onload="setTimeout(fireFoo, 0)">
-  Test for bug 291653
-  </body>
-</html>
diff --git a/dom/tests/mochitest/bugs/file_bug504862.html b/dom/tests/mochitest/bugs/file_bug504862.html
deleted file mode 100644
index dc11ced6f..000000000
--- a/dom/tests/mochitest/bugs/file_bug504862.html
+++ /dev/null
@@ -1,22 +0,0 @@
-<html>
-<body>
-<script>
-window.returnValue = 3;
-
-if (location.toString().match(/^http:\/\/mochi.test:8888/)) {
-  // Test that we got the right arguments.
-  opener.is(window.dialogArguments, "my args",
-            "dialog did not get the right arguments.");
-
-  // Load a different url, and test that it sees the arguments (since it's same origin).
-  window.location="data:text/html,<html><body onload=\"opener.is(window.dialogArguments, 'my args', 'subsequent dialog document did not get the right arguments.'); close();\">';";
-} else {
-  // Post a message containing our arguments to the opener to test
-  // that this cross origing dialog does *not* see the passed in
-  // arguments.
-  opener.postMessage("args: " + window.dialogArguments,
-                     "http://mochi.test:8888");
-
-  close();
-}
-</script>
diff --git a/dom/tests/mochitest/bugs/mochitest.ini b/dom/tests/mochitest/bugs/mochitest.ini
index 309aab6e0..3743c6782 100644
--- a/dom/tests/mochitest/bugs/mochitest.ini
+++ b/dom/tests/mochitest/bugs/mochitest.ini
@@ -10,9 +10,6 @@ support-files =
   child_bug260264.html
   devicemotion_inner.html
   devicemotion_outer.html
-  file_bug291653.html
-  file_bug406375.html
-  file_bug504862.html
   file_bug593174_1.html
   file_bug593174_2.html
   file_bug809290_b1.html
@@ -45,7 +42,6 @@ skip-if = toolkit == 'android'
 [test_bug260264_nested.html]
 [test_bug265203.html]
 [test_bug291377.html]
-[test_bug291653.html]
 skip-if = toolkit == 'android' #TIMED_OUT
 [test_bug304459.html]
 [test_bug308856.html]
@@ -67,28 +63,21 @@ skip-if = toolkit == 'android' #TIMED_OUT
 [test_bug396843.html]
 [test_bug400204.html]
 [test_bug404748.html]
-[test_bug406375.html]
-skip-if = toolkit == 'android'
-[test_bug414291.html]
-tags = openwindow
 [test_bug427744.html]
 skip-if = toolkit == 'android'
 [test_bug42976.html]
 [test_bug430276.html]
-[test_bug437361.html]
 skip-if = toolkit == 'android'
 [test_bug440572.html]
 [test_bug456151.html]
 [test_bug458091.html]
 [test_bug459848.html]
 [test_bug465263.html]
-[test_bug479143.html]
 skip-if = toolkit == 'android'
 [test_bug484775.html]
 [test_bug492925.html]
 [test_bug49312.html]
 [test_bug495219.html]
-[test_bug504862.html]
 skip-if = toolkit == 'android' #RANDOM
 [test_bug529328.html]
 [test_bug531176.html]
@@ -126,7 +115,6 @@ skip-if = toolkit == 'android'
 [test_bug698061.html]
 [test_bug698551.html]
 [test_bug707749.html]
-[test_bug735237.html]
 [test_bug739038.html]
 [test_bug740811.html]
 [test_bug743615.html]
diff --git a/dom/tests/mochitest/bugs/test_bug291653.html b/dom/tests/mochitest/bugs/test_bug291653.html
deleted file mode 100644
index 1543cdd96..000000000
--- a/dom/tests/mochitest/bugs/test_bug291653.html
+++ /dev/null
@@ -1,56 +0,0 @@
-<!DOCTYPE HTML>
-<html>
-<!--
-https://bugzilla.mozilla.org/show_bug.cgi?id=291653
--->
-<head>
-  <title>Test for Bug 291653</title>
-  <script type="application/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
-  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
-</head>
-<body>
-<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=291653">Mozilla Bug 291653</a>
-<p id="display"></p>
-<div id="content" style="display: none">
-  
-</div>
-<pre id="test">
-<script type="application/javascript">
-
-/** Test for Bug 291653 **/
-SimpleTest.waitForExplicitFinish();
-SimpleTest.requestFlakyTimeout("untriaged");
-
-var secondListenerDidRun = false;
-
-var w;
-function start() {
-  if ("showModalDialog" in window) {
-    w = window.open("file_bug291653.html", "foo", "width=300,height=300");
-  } else {
-    // window.showModalDialog doesn't exist in e10s mode, nothing to do in this test.
-    ok(true, "nothing to do in e10s mode");
-    SimpleTest.finish();
-  }
-}
-
-function closeTest() {
-  w.setTimeout("close()", 0);
-  setTimeout("finish()", 500);
-}
-
-function finish() {
-  ok(!secondListenerDidRun, "Shouldn't have run second listener!");
-  SimpleTest.finish();
-}
-
-function end() {
-  setTimeout("closeTest()", 500);
-}
-
-start();
-
-</script>
-</pre>
-</body>
-</html>
diff --git a/dom/tests/mochitest/bugs/test_bug406375.html b/dom/tests/mochitest/bugs/test_bug406375.html
deleted file mode 100644
index 2cd459ffa..000000000
--- a/dom/tests/mochitest/bugs/test_bug406375.html
+++ /dev/null
@@ -1,37 +0,0 @@
-<!DOCTYPE HTML>
-<html>
-<!--
-https://bugzilla.mozilla.org/show_bug.cgi?id=406375
--->
-<head>
-  <title>Test for Bug 406375</title>
-  <script type="application/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
-  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
-</head>
-<body onload="runTest()">
-<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=406375">Mozilla Bug 406375</a>
-<p id="display"></p>
-<div id="content" style="display: none">
-  
-</div>
-<pre id="test">
-<script type="application/javascript">
-
-/** Test for Bug 406375 **/
-
-
-SimpleTest.waitForExplicitFinish();
-
-function runTest() {
-  if ("showModalDialog" in window) {
-    window.showModalDialog("file_bug406375.html");
-  }
-  ok(true, "This test should not hang");
-
-  SimpleTest.finish();
-}
-
-</script>
-</pre>
-</body>
-</html>
diff --git a/dom/tests/mochitest/bugs/test_bug414291.html b/dom/tests/mochitest/bugs/test_bug414291.html
index 883e52bb4..0ee5cb393 100644
--- a/dom/tests/mochitest/bugs/test_bug414291.html
+++ b/dom/tests/mochitest/bugs/test_bug414291.html
@@ -16,7 +16,6 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=414291
 
 var result1 = 0;
 var result2 = 0;
-var result3 = 0;
 
 window.open("data:text/html,<html><body onload='close(); opener.result1 = 1;'>", "w1");
 is(result1, 0, "window should not be opened either as modal or loaded synchronously.");
@@ -24,11 +23,6 @@ is(result1, 0, "window should not be opened either as modal or loaded synchronou
 window.open("data:text/html,<html><body onload='close(); opener.result2 = 2;'>", "w2", "modal=yes");
 is(result2, 0, "window should not be opened either as modal or data loaded synchronously.");
 
-if (window.showModalDialog) {
-  result3 = window.showModalDialog("data:text/html,<html><body onload='close(); returnValue = 3;'>");
-  is(result3, 3, "window should be opened as modal.");
-}
-
 </script>
 </pre>
 </body>
diff --git a/dom/tests/mochitest/bugs/test_bug437361.html b/dom/tests/mochitest/bugs/test_bug437361.html
deleted file mode 100644
index ecc2cb08d..000000000
--- a/dom/tests/mochitest/bugs/test_bug437361.html
+++ /dev/null
@@ -1,72 +0,0 @@
-<!DOCTYPE HTML>
-<html>
-<!--
-https://bugzilla.mozilla.org/show_bug.cgi?id=437361
--->
-<head>
-  <title>Test for Bug 437361</title>
-  <script type="text/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
-  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
-  
-  <script class="testbody" type="text/javascript">
-
-  /** Test for Bug 437361 **/
-
-  function testModalDialogBlockedCleanly() {
-    is(true, SpecialPowers.getBoolPref("dom.disable_open_during_load"), "mozprefs sanity check");
-    var rv = window.showModalDialog( // should be blocked without exception
-      "data:text/html,<html><body onload='close(); returnValue = 1;' /></html>");
-    is(rv, null, "Modal dialog opened unexpectedly.");
-  }
-  
-  function testModalDialogAllowed() {
-    is(false, SpecialPowers.getBoolPref("dom.disable_open_during_load"), "mozprefs sanity check");
-    var rv = window.showModalDialog( // should not be blocked this time
-      "data:text/html,<html><body onload='close(); returnValue = 1;' /></html>");
-    is(rv, 1, "Problem with modal dialog returnValue.");
-  }
-
-  function testOtherExceptionsNotTrapped() {
-    is(false, SpecialPowers.getBoolPref("dom.disable_open_during_load"), "mozprefs sanity check");
-    window.showModalDialog('about:config'); // forbidden by SecurityCheckURL
-  }
-
-  function test(disableOpen, exceptionExpected, testFn, errorMsg) {
-    if ("showModalDialog" in window) {
-      var oldPrefVal = SpecialPowers.getBoolPref("dom.disable_open_during_load");
-      try {
-        SpecialPowers.setBoolPref("dom.disable_open_during_load", disableOpen);
-        testFn();
-        ok(!exceptionExpected, errorMsg);
-      } catch (_) {
-        ok(exceptionExpected, errorMsg);
-      }
-      finally {
-        SpecialPowers.setBoolPref("dom.disable_open_during_load", oldPrefVal);
-      }
-    } else {
-      ok(true, "nothing to do in e10s mode");
-    }
-  }
-
-  test(true, false, testModalDialogBlockedCleanly,
-       "Blocked showModalDialog caused an exception.");
-       
-  test(false, false, testModalDialogAllowed,
-       "showModalDialog was blocked even though dom.disable_open_during_load was false.");
-
-  test(false, true, testOtherExceptionsNotTrapped,
-       "Incorrectly suppressed insecure showModalDialog exception.");
-
-  </script>
-</head>
-<body>
-<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=437361">Mozilla Bug 437361</a>
-<p id="display"></p>
-<div id="content" style="display: none"> 
-</div>
-<pre id="test">
-</pre>
-</body>
-</html>
-
diff --git a/dom/tests/mochitest/bugs/test_bug479143.html b/dom/tests/mochitest/bugs/test_bug479143.html
deleted file mode 100644
index 03db4ddea..000000000
--- a/dom/tests/mochitest/bugs/test_bug479143.html
+++ /dev/null
@@ -1,44 +0,0 @@
-<!DOCTYPE html>
-<html>
-<!--
-https://bugzilla.mozilla.org/show_bug.cgi?id=479143
--->
-<head>
-  <title>Test for Bug 411103</title>
-  <script type="text/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
-  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
-</head>
-<body>
-<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=479143">Mozilla Bug 479143</a>
-<p id="display"></p>
-<div id="content" style="display: none"></div>
-
-<pre id="test">
-<script class="testbody" type="text/javascript">
-
-  SimpleTest.waitForExplicitFinish();
-
-  setTimeout(function() {
-    if ("showModalDialog" in window) {
-      var interval = setInterval(function() { var i = 0; i++; }, 10);
-
-      var xhr = new XMLHttpRequest();
-      xhr.open("GET", "test_bug479143.html", false);
-      xhr.send(null);
-
-      window.showModalDialog("javascript:" +
-                             "setTimeout(function() { window.close(); }, 1000);",
-                             null);
-
-      clearInterval(interval);
-    }
-
-    ok(true, "did not crash");
-
-    SimpleTest.finish();
-  }, 0);
-
-</script>
-</pre>
-</body>
-</html>
diff --git a/dom/tests/mochitest/bugs/test_bug504862.html b/dom/tests/mochitest/bugs/test_bug504862.html
deleted file mode 100644
index 713165bc3..000000000
--- a/dom/tests/mochitest/bugs/test_bug504862.html
+++ /dev/null
@@ -1,45 +0,0 @@
-<!DOCTYPE HTML>
-<html>
-<!--
-https://bugzilla.mozilla.org/show_bug.cgi?id=504862
--->
-<head>
-  <title>Test for Bug 504862</title>
-  <script type="text/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
-  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
-</head>
-<body onload="runTest()">
-<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=504862">Mozilla Bug 504862</a>
-<script class="testbody" type="text/javascript">
-
-/** Test for Bug 504862 **/
-SimpleTest.waitForExplicitFinish();
-function onMsgRcv(event)
-{
-  is(event.data, "args: undefined", "Unexpected cross origin dialog arguments.");
-}
-
-function runTest() {
-  if ("showModalDialog" in window) {
-    window.addEventListener("message", onMsgRcv, false);
-
-    var result = window.showModalDialog("file_bug504862.html", "my args");
-    // NB: We used to clear returnValue on each navigation, but now we do a
-    // security check on access, so we can safely make returnValue live on
-    // the browsing context, per spec.
-    is(result, 3, "window sees previous dialog documents return value.");
-
-    result = window.showModalDialog("http://test1.example.com/tests/dom/tests/mochitest/bugs/file_bug504862.html", "my args");
-
-    is(result, undefined, "Able to see return value from cross origin dialog.");
-  } else {
-    ok(true, "nothing to do in e10s mode");
-  }
-
-  SimpleTest.finish();
-}
-
-</script>
-</pre>
-</body>
-</html>
diff --git a/dom/tests/mochitest/bugs/test_bug61098.html b/dom/tests/mochitest/bugs/test_bug61098.html
index 4c6ce967d..ed16e099b 100644
--- a/dom/tests/mochitest/bugs/test_bug61098.html
+++ b/dom/tests/mochitest/bugs/test_bug61098.html
@@ -306,28 +306,6 @@ function runtestsInner()
 
   w.close();
 
-  // Test that showModalDialog() works normally and then gets blocked
-  // on the second call.
-  if (window.showModalDialog) {
-    w = window.open();
-    w.showModalDialog("data:text/html,%3Cscript>window.close();%3C/script>")
-    is (promptState, void(0), "Wrong prompt state");
-
-    try {
-      w.showModalDialog("data:text/html,%3Cscript>window.close();%3C/script>")
-      ok(false, "showModalDialog call should throw an exception");
-    } catch(e) {
-      is(e.name, "NS_ERROR_NOT_AVAILABLE", "Wrong exception");
-    }
-    is (promptState.method, "confirm", "Wrong prompt method called");
-    is (promptState.parent, w, "Wrong confirm parent");
-    is (promptState.msg, "Prevent this page from creating additional dialogs",
-        "Wrong confirm message");
-    promptState = void(0);
-
-    w.close();
-  }
-
   mockPromptFactoryRegisterer.unregister();
   mockPromptServiceRegisterer.unregister();
 
diff --git a/dom/tests/mochitest/bugs/test_bug735237.html b/dom/tests/mochitest/bugs/test_bug735237.html
deleted file mode 100644
index e1a25a425..000000000
--- a/dom/tests/mochitest/bugs/test_bug735237.html
+++ /dev/null
@@ -1,38 +0,0 @@
-<!DOCTYPE HTML>
-<html>
-<!--
-https://bugzilla.mozilla.org/show_bug.cgi?id=735237
--->
-<head>
-  <title>Test for Bug 735237</title>
-  <script type="application/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
-  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
-</head>
-<body>
-<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=735237">Mozilla Bug 735237</a>
-<p id="display"></p>
-<div id="content" style="display: none">
-
-</div>
-<pre id="test">
-<script class="testbody" type="text/javascript">
-
-/** Test for Bug 735237 **/
-
-SimpleTest.waitForExplicitFinish();
-
-SpecialPowers.pushPrefEnv({"set": [["dom.disable_window_showModalDialog", true]]}, function() {
-  var caughtException = false;
-  try {
-    window.showModalDialog("http://example.com/");
-  } catch (e) {
-    caughtException = true;
-  }
-  ok(caughtException, "showModalDialog should throw an exception");
-  SimpleTest.finish();
-});
-
-</script>
-</pre>
-</body>
-</html>
diff --git a/dom/tests/mochitest/general/file_showModalDialog.html b/dom/tests/mochitest/general/file_showModalDialog.html
deleted file mode 100644
index 1cae0b1c0..000000000
--- a/dom/tests/mochitest/general/file_showModalDialog.html
+++ /dev/null
@@ -1,35 +0,0 @@
-<!DOCTYPE html>
-<html>
-<head>
-<script>
-  function go() {
-    is(SpecialPowers.wrap(window).location.toString(), location.toString(), "sanity");
-    ok("returnValue" in window && "dialogArguments" in window, "We are modal");
-    var iwin = document.getElementById('ifr').contentWindow;
-    is(SpecialPowers.Cu.getClassName(iwin, /* aUnwrap = */ true), "Window", "Descendant frames should not be modal");
-
-    if (location.origin != "http://mochi.test:8888") {
-      is(window.dialogArguments, undefined,
-        "dialogArguments should be undefined cross-origin: " + location.origin);
-    }
-
-    window.returnValue = "rv: " + window.dialogArguments;
-
-    // Allow for testing navigations in series.
-    if (location.search == "") {
-      window.close();
-    } else {
-      var origins = location.search.split('?')[1].split(',');
-      var newsearch = '?' + origins.splice(1).join(',');
-      var newurl = location.toString().replace(location.origin, origins[0])
-                                      .replace(location.search, newsearch);
-      location = newurl;
-    }
-
-  }
-</script>
-</head>
-<body onload="opener.postMessage('dosetup', '*');">
-<iframe id="ifr"></iframe>
-</body>
-</html>
diff --git a/dom/tests/mochitest/general/mochitest.ini b/dom/tests/mochitest/general/mochitest.ini
index d00ea1d4b..9f2fad785 100755
--- a/dom/tests/mochitest/general/mochitest.ini
+++ b/dom/tests/mochitest/general/mochitest.ini
@@ -9,7 +9,6 @@ support-files =
   file_interfaces.xml
   file_moving_nodeList.html
   file_moving_xhr.html
-  file_showModalDialog.html
   historyframes.html
   image_50.png
   image_100.png
@@ -116,8 +115,6 @@ support-files = test_offsets.js
 [test_resource_timing_frameset.html]
 [test_selectevents.html]
 skip-if = toolkit == 'android' # bug 1230232 - Mouse doesn't select in the same way
-[test_showModalDialog.html]
-skip-if = e10s || toolkit == 'android' #Don't run modal tests on Android
 [test_showModalDialog_e10s.html]
 run-if = e10s
 [test_storagePermissionsAccept.html]
diff --git a/dom/tests/mochitest/general/test_showModalDialog.html b/dom/tests/mochitest/general/test_showModalDialog.html
deleted file mode 100644
index 511c79e63..000000000
--- a/dom/tests/mochitest/general/test_showModalDialog.html
+++ /dev/null
@@ -1,60 +0,0 @@
-<!DOCTYPE HTML>
-<html>
-<!--
-https://bugzilla.mozilla.org/show_bug.cgi?id=862918
--->
-<head>
-  <meta charset="utf-8">
-  <title>Test for Bug 862918</title>
-  <script type="application/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
-  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
-  <script type="application/javascript">
-
-  /** Test for window.showModalDialog. **/
-
-  // The modal window needs to touch Cu, which means that it needs
-  // SpecialPowers. But given the semantics of modal windows, we have to
-  // do some funny stuff with postMessage to set this up.
-  window.onmessage = function(evt) {
-    is(evt.data, 'dosetup', "message from modal window is correct");
-    var win = SpecialPowers.wrap(evt.source);
-    win.wrappedJSObject.SpecialPowers = SpecialPowers;
-    SpecialPowers.setWrapped(win.wrappedJSObject, 'is', SpecialPowers.wrap(is));
-    SpecialPowers.setWrapped(win.wrappedJSObject, 'ok', SpecialPowers.wrap(ok));
-    win.wrappedJSObject.go();
-  };
-
-  var someObj = { foo: 42, bar: "hi"};
-  var xurl = location.toString()
-                     .replace('mochi.test:8888', 'example.org')
-                     .replace('test_showModal', 'file_showModal');
-  if (xurl.indexOf('?') != -1)
-    xurl = xurl.substring(0, xurl.indexOf('?'));
-  is(showModalDialog('file_showModalDialog.html'), "rv: undefined");
-  is(showModalDialog(xurl), undefined);
-  is(showModalDialog('file_showModalDialog.html', 3), "rv: 3");
-  is(showModalDialog(xurl, 3), undefined);
-  is(showModalDialog('file_showModalDialog.html', someObj), "rv: " + someObj);
-  is(showModalDialog(xurl, someObj), undefined);
-
-  // Test sequential navigations.
-  is(showModalDialog('file_showModalDialog.html?http://mochi.test:8888', 4),
-                     'rv: 4');
-  is(showModalDialog('file_showModalDialog.html?http://example.com', 4), undefined);
-  is(showModalDialog('file_showModalDialog.html?http://example.com,http://mochi.test:8888', 4), 'rv: 4');
-
-  // This test used to assert after gc. Make sure it doesn't.
-  SpecialPowers.gc();
-
-  </script>
-</head>
-<body>
-<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=862918">Mozilla Bug 862918</a>
-<p id="display"></p>
-<div id="content" style="display: none">
-
-</div>
-<pre id="test">
-</pre>
-</body>
-</html>
diff --git a/dom/webidl/Window.webidl b/dom/webidl/Window.webidl
index 468f1cc8a..ab03bf40b 100644
--- a/dom/webidl/Window.webidl
+++ b/dom/webidl/Window.webidl
@@ -78,9 +78,6 @@ typedef any Transferable;
   [Throws, UnsafeInPrerendering, NeedsSubjectPrincipal] boolean confirm(optional DOMString message = "");
   [Throws, UnsafeInPrerendering, NeedsSubjectPrincipal] DOMString? prompt(optional DOMString message = "", optional DOMString default = "");
   [Throws, UnsafeInPrerendering] void print();
-  //[Throws] any showModalDialog(DOMString url, optional any argument);
-  [Throws, Func="nsGlobalWindow::IsShowModalDialogEnabled", UnsafeInPrerendering, NeedsSubjectPrincipal]
-  any showModalDialog(DOMString url, optional any argument, optional DOMString options = "");
 
   [Throws, CrossOriginCallable, NeedsSubjectPrincipal]
   void postMessage(any message, DOMString targetOrigin, optional sequence<Transferable> transfer);
@@ -240,17 +237,6 @@ interface SpeechSynthesisGetter {
 Window implements SpeechSynthesisGetter;
 #endif
 
-// http://www.whatwg.org/specs/web-apps/current-work/
-[NoInterfaceObject]
-interface WindowModal {
-  [Throws, Func="nsGlobalWindow::IsModalContentWindow", NeedsSubjectPrincipal]
-  readonly attribute any dialogArguments;
-
-  [Throws, Func="nsGlobalWindow::IsModalContentWindow", NeedsSubjectPrincipal]
-  attribute any returnValue;
-};
-Window implements WindowModal;
-
 // Mozilla-specific stuff
 partial interface Window {
   //[NewObject, Throws] CSSStyleDeclaration getDefaultComputedStyle(Element elt, optional DOMString pseudoElt = "");
diff --git a/embedding/browser/nsIWebBrowserChrome.idl b/embedding/browser/nsIWebBrowserChrome.idl
index 40f03cbe4..32dba4219 100644
--- a/embedding/browser/nsIWebBrowserChrome.idl
+++ b/embedding/browser/nsIWebBrowserChrome.idl
@@ -77,9 +77,6 @@ interface nsIWebBrowserChrome : nsISupports
     const unsigned long CHROME_NON_PRIVATE_WINDOW     = 0x00020000;
     const unsigned long CHROME_PRIVATE_LIFETIME       = 0x00040000;
 
-    // Whether this was opened by nsGlobalWindow::ShowModalDialog.
-    const unsigned long CHROME_MODAL_CONTENT_WINDOW   = 0x00080000;
-
     // Whether this window should use remote (out-of-process) tabs.
     const unsigned long CHROME_REMOTE_WINDOW          = 0x00100000;
 
diff --git a/embedding/components/windowwatcher/nsWindowWatcher.cpp b/embedding/components/windowwatcher/nsWindowWatcher.cpp
index e0e8b4bef..3732ea66d 100644
--- a/embedding/components/windowwatcher/nsWindowWatcher.cpp
+++ b/embedding/components/windowwatcher/nsWindowWatcher.cpp
@@ -683,7 +683,6 @@ nsWindowWatcher::OpenWindowInternal(mozIDOMWindowProxy* aParent,
   bool windowNeedsName = false;
   bool windowIsModal = false;
   bool uriToLoadIsChrome = false;
-  bool windowIsModalContentDialog = false;
 
   uint32_t chromeFlags;
   nsAutoString name;          // string version of aName
@@ -775,30 +774,12 @@ nsWindowWatcher::OpenWindowInternal(mozIDOMWindowProxy* aParent,
   } else {
     chromeFlags = CalculateChromeFlagsForChild(features);
 
-    // Until ShowModalDialog is removed, it's still possible for content to
-    // request dialogs, but only in single-process mode.
     if (aDialog) {
       MOZ_ASSERT(XRE_IsParentProcess());
       chromeFlags |= nsIWebBrowserChrome::CHROME_OPENAS_DIALOG;
     }
   }
 
-  // If we're not called through our JS version of the API, and we got
-  // our internal modal option, treat the window we're opening as a
-  // modal content window (and set the modal chrome flag).
-  if (!aCalledFromJS && aArgv &&
-      WinHasOption(features, "-moz-internal-modal", 0, nullptr)) {
-    windowIsModalContentDialog = true;
-
-    // CHROME_MODAL gets inherited by dependent windows, which affects various
-    // platform-specific window state (especially on OSX). So we need some way
-    // to determine that this window was actually opened by nsGlobalWindow::
-    // ShowModalDialog(), and that somebody is actually going to be watching
-    // for return values and all that.
-    chromeFlags |= nsIWebBrowserChrome::CHROME_MODAL_CONTENT_WINDOW;
-    chromeFlags |= nsIWebBrowserChrome::CHROME_MODAL;
-  }
-
   SizeSpec sizeSpec;
   CalcSizeSpec(features, sizeSpec);
 
@@ -1079,7 +1060,7 @@ nsWindowWatcher::OpenWindowInternal(mozIDOMWindowProxy* aParent,
     MaybeDisablePersistence(features, newTreeOwner);
   }
 
-  if ((aDialog || windowIsModalContentDialog) && aArgv) {
+  if (aDialog && aArgv) {
     // Set the args on the new window.
     nsCOMPtr<nsPIDOMWindowOuter> piwin(do_QueryInterface(*aResult));
     NS_ENSURE_TRUE(piwin, NS_ERROR_UNEXPECTED);
@@ -1268,8 +1249,7 @@ nsWindowWatcher::OpenWindowInternal(mozIDOMWindowProxy* aParent,
     SizeOpenedWindow(newTreeOwner, aParent, isCallerChrome, sizeSpec);
   }
 
-  // XXXbz isn't windowIsModal always true when windowIsModalContentDialog?
-  if (windowIsModal || windowIsModalContentDialog) {
+  if (windowIsModal) {
     nsCOMPtr<nsIDocShellTreeOwner> newTreeOwner;
     newDocShellItem->GetTreeOwner(getter_AddRefs(newTreeOwner));
     nsCOMPtr<nsIWebBrowserChrome> newChrome(do_GetInterface(newTreeOwner));
diff --git a/modules/libpref/init/all.js b/modules/libpref/init/all.js
index 8f7ae0a58..c5daf9213 100644
--- a/modules/libpref/init/all.js
+++ b/modules/libpref/init/all.js
@@ -1166,7 +1166,6 @@ pref("dom.disable_window_open_feature.menubar",     false);
 pref("dom.disable_window_open_feature.resizable",   true);
 pref("dom.disable_window_open_feature.minimizable", false);
 pref("dom.disable_window_open_feature.status",      true);
-pref("dom.disable_window_showModalDialog",          true);
 
 pref("dom.allow_scripts_to_close_windows",          false);