diff --git a/accessible/generic/ImageAccessible.cpp b/accessible/generic/ImageAccessible.cpp
index 05f90a485c56..cd3c0003f79a 100644
--- a/accessible/generic/ImageAccessible.cpp
+++ b/accessible/generic/ImageAccessible.cpp
@@ -13,6 +13,7 @@
 #include "imgIContainer.h"
 #include "imgIRequest.h"
 #include "nsGenericHTMLElement.h"
+#include "mozilla/dom/BrowsingContext.h"
 #include "mozilla/dom/Document.h"
 #include "nsIImageLoadingContent.h"
 #include "nsIServiceManager.h"
@@ -109,7 +110,7 @@ bool ImageAccessible::DoAction(uint8_t aIndex) const {
   nsCOMPtr<nsPIDOMWindowOuter> piWindow = document->GetWindow();
   if (!piWindow) return false;
 
-  nsCOMPtr<nsPIDOMWindowOuter> tmp;
+  RefPtr<mozilla::dom::BrowsingContext> tmp;
   return NS_SUCCEEDED(piWindow->Open(spec, EmptyString(), EmptyString(),
                                      /* aLoadInfo = */ nullptr,
                                      /* aForceNoOpener = */ false,
diff --git a/browser/base/content/browser.js b/browser/base/content/browser.js
index d395f5aa401d..082922e72362 100644
--- a/browser/base/content/browser.js
+++ b/browser/base/content/browser.js
@@ -6485,7 +6485,7 @@ nsBrowserAccess.prototype = {
       throw Cr.NS_ERROR_FAILURE;
     }
 
-    var newWindow = null;
+    var browsingContext = null;
     var isExternal = !!(aFlags & Ci.nsIBrowserDOMWindow.OPEN_EXTERNAL);
 
     if (aOpener && isExternal) {
@@ -6549,7 +6549,7 @@ nsBrowserAccess.prototype = {
         // Pass all params to openDialog to ensure that "url" isn't passed through
         // loadOneOrMoreURIs, which splits based on "|"
         try {
-          newWindow = openDialog(
+          openDialog(
             AppConstants.BROWSER_CHROME_URL,
             "_blank",
             features,
@@ -6566,6 +6566,17 @@ nsBrowserAccess.prototype = {
             null,
             aCsp
           );
+          // At this point, the new browser window is just starting to load, and
+          // hasn't created the content <browser> that we should return. So we
+          // can't actually return a valid BrowsingContext for this load without
+          // spinning the event loop.
+          //
+          // Fortunately, no current callers of this API who pass OPEN_NEWWINDOW
+          // actually use the return value, so we're safe returning null for
+          // now.
+          //
+          // Ideally this should be fixed.
+          browsingContext = null;
         } catch (ex) {
           Cu.reportError(ex);
         }
@@ -6599,12 +6610,13 @@ nsBrowserAccess.prototype = {
           aCsp
         );
         if (browser) {
-          newWindow = browser.contentWindow;
+          browsingContext = browser.browsingContext;
         }
         break;
       default:
         // OPEN_CURRENTWINDOW or an illegal value
-        newWindow = window.content;
+        browsingContext =
+          window.content && BrowsingContext.getFromWindow(window.content);
         if (aURI) {
           let loadflags = isExternal
             ? Ci.nsIWebNavigation.LOAD_FLAGS_FROM_EXTERNAL
@@ -6622,7 +6634,7 @@ nsBrowserAccess.prototype = {
           window.focus();
         }
     }
-    return newWindow;
+    return browsingContext;
   },
 
   createContentWindowInFrame: function browser_createContentWindowInFrame(
diff --git a/docshell/base/nsDocShell.cpp b/docshell/base/nsDocShell.cpp
index dcbff46d509e..af5c2a3b0d89 100644
--- a/docshell/base/nsDocShell.cpp
+++ b/docshell/base/nsDocShell.cpp
@@ -8777,7 +8777,7 @@ nsresult nsDocShell::PerformRetargeting(nsDocShellLoadState* aLoadState,
     nsCOMPtr<nsPIDOMWindowOuter> win = GetWindow();
     NS_ENSURE_TRUE(win, NS_ERROR_NOT_AVAILABLE);
 
-    nsCOMPtr<nsPIDOMWindowOuter> newWin;
+    RefPtr<BrowsingContext> newBC;
     nsAutoCString spec;
     aLoadState->URI()->GetSpec(spec);
 
@@ -8837,20 +8837,21 @@ nsresult nsDocShell::PerformRetargeting(nsDocShellLoadState* aLoadState,
                      EmptyString(),         // Features
                      loadState,
                      true,  // aForceNoOpener
-                     getter_AddRefs(newWin));
-      MOZ_ASSERT(!newWin);
+                     getter_AddRefs(newBC));
+      MOZ_ASSERT(!newBC);
       return rv;
     }
 
     rv = win->OpenNoNavigate(NS_ConvertUTF8toUTF16(spec),
                              aLoadState->Target(),  // window name
                              EmptyString(),         // Features
-                             getter_AddRefs(newWin));
+                             getter_AddRefs(newBC));
 
     // In some cases the Open call doesn't actually result in a new
     // window being opened.  We can detect these cases by examining the
-    // document in |newWin|, if any.
-    nsCOMPtr<nsPIDOMWindowOuter> piNewWin = newWin;
+    // document in |newBC|, if any.
+    nsCOMPtr<nsPIDOMWindowOuter> piNewWin =
+        newBC ? newBC->GetDOMWindow() : nullptr;
     if (piNewWin) {
       RefPtr<Document> newDoc = piNewWin->GetExtantDoc();
       if (!newDoc || newDoc->IsInitialDocument()) {
@@ -8858,8 +8859,9 @@ nsresult nsDocShell::PerformRetargeting(nsDocShellLoadState* aLoadState,
       }
     }
 
-    nsCOMPtr<nsIWebNavigation> webNav = do_GetInterface(newWin);
-    targetDocShell = do_QueryInterface(webNav);
+    if (newBC) {
+      targetDocShell = newBC->GetDocShell();
+    }
   }
 
   NS_ENSURE_SUCCESS(rv, rv);
diff --git a/dom/base/Document.cpp b/dom/base/Document.cpp
index 8b79a83fbc74..b7ab6ea296ee 100644
--- a/dom/base/Document.cpp
+++ b/dom/base/Document.cpp
@@ -8709,12 +8709,12 @@ mozilla::dom::Nullable<mozilla::dom::WindowProxyHolder> Document::Open(
     return nullptr;
   }
   RefPtr<nsGlobalWindowOuter> win = nsGlobalWindowOuter::Cast(outer);
-  nsCOMPtr<nsPIDOMWindowOuter> newWindow;
-  rv = win->OpenJS(aURL, aName, aFeatures, getter_AddRefs(newWindow));
-  if (!newWindow) {
+  RefPtr<BrowsingContext> newBC;
+  rv = win->OpenJS(aURL, aName, aFeatures, getter_AddRefs(newBC));
+  if (!newBC) {
     return nullptr;
   }
-  return WindowProxyHolder(newWindow->GetBrowsingContext());
+  return WindowProxyHolder(newBC.forget());
 }
 
 Document* Document::Open(const Optional<nsAString>& /* unused */,
diff --git a/dom/base/nsGlobalWindowOuter.cpp b/dom/base/nsGlobalWindowOuter.cpp
index 07a827dc8c69..ab10192b931f 100644
--- a/dom/base/nsGlobalWindowOuter.cpp
+++ b/dom/base/nsGlobalWindowOuter.cpp
@@ -5734,10 +5734,9 @@ void nsGlobalWindowOuter::FireAbuseEvents(
 Nullable<WindowProxyHolder> nsGlobalWindowOuter::OpenOuter(
     const nsAString& aUrl, const nsAString& aName, const nsAString& aOptions,
     ErrorResult& aError) {
-  nsCOMPtr<nsPIDOMWindowOuter> window;
-  aError = OpenJS(aUrl, aName, aOptions, getter_AddRefs(window));
   RefPtr<BrowsingContext> bc;
-  if (!window || !(bc = window->GetBrowsingContext())) {
+  aError = OpenJS(aUrl, aName, aOptions, getter_AddRefs(bc));
+  if (!bc) {
     return nullptr;
   }
   return WindowProxyHolder(bc.forget());
@@ -5748,7 +5747,7 @@ nsresult nsGlobalWindowOuter::Open(const nsAString& aUrl,
                                    const nsAString& aOptions,
                                    nsDocShellLoadState* aLoadState,
                                    bool aForceNoOpener,
-                                   nsPIDOMWindowOuter** _retval) {
+                                   BrowsingContext** _retval) {
   return OpenInternal(aUrl, aName, aOptions,
                       false,             // aDialog
                       false,             // aContentModal
@@ -5762,7 +5761,7 @@ nsresult nsGlobalWindowOuter::Open(const nsAString& aUrl,
 nsresult nsGlobalWindowOuter::OpenJS(const nsAString& aUrl,
                                      const nsAString& aName,
                                      const nsAString& aOptions,
-                                     nsPIDOMWindowOuter** _retval) {
+                                     BrowsingContext** _retval) {
   return OpenInternal(aUrl, aName, aOptions,
                       false,             // aDialog
                       false,             // aContentModal
@@ -5781,7 +5780,7 @@ nsresult nsGlobalWindowOuter::OpenDialog(const nsAString& aUrl,
                                          const nsAString& aName,
                                          const nsAString& aOptions,
                                          nsISupports* aExtraArgument,
-                                         nsPIDOMWindowOuter** _retval) {
+                                         BrowsingContext** _retval) {
   return OpenInternal(aUrl, aName, aOptions,
                       true,                     // aDialog
                       false,                    // aContentModal
@@ -5799,7 +5798,7 @@ nsresult nsGlobalWindowOuter::OpenDialog(const nsAString& aUrl,
 nsresult nsGlobalWindowOuter::OpenNoNavigate(const nsAString& aUrl,
                                              const nsAString& aName,
                                              const nsAString& aOptions,
-                                             nsPIDOMWindowOuter** _retval) {
+                                             BrowsingContext** _retval) {
   return OpenInternal(aUrl, aName, aOptions,
                       false,             // aDialog
                       false,             // aContentModal
@@ -5824,7 +5823,7 @@ Nullable<WindowProxyHolder> nsGlobalWindowOuter::OpenDialogOuter(
     return nullptr;
   }
 
-  nsCOMPtr<nsPIDOMWindowOuter> dialog;
+  RefPtr<BrowsingContext> dialog;
   aError = OpenInternal(aUrl, aName, aOptions,
                         true,                // aDialog
                         false,               // aContentModal
@@ -5835,11 +5834,10 @@ Nullable<WindowProxyHolder> nsGlobalWindowOuter::OpenDialogOuter(
                         nullptr,             // aLoadState
                         false,               // aForceNoOpener
                         getter_AddRefs(dialog));
-  RefPtr<BrowsingContext> bc;
-  if (!dialog || !(bc = dialog->GetBrowsingContext())) {
+  if (!dialog) {
     return nullptr;
   }
-  return WindowProxyHolder(bc.forget());
+  return WindowProxyHolder(dialog.forget());
 }
 
 BrowsingContext* nsGlobalWindowOuter::GetFramesOuter() {
@@ -7131,7 +7129,7 @@ nsresult nsGlobalWindowOuter::OpenInternal(
     bool aDialog, bool aContentModal, bool aCalledNoScript, bool aDoJSFixups,
     bool aNavigate, nsIArray* argv, nsISupports* aExtraArgument,
     nsDocShellLoadState* aLoadState, bool aForceNoOpener,
-    nsPIDOMWindowOuter** aReturn) {
+    BrowsingContext** aReturn) {
 #ifdef DEBUG
   uint32_t argc = 0;
   if (argv) argv->GetLength(&argc);
@@ -7248,7 +7246,7 @@ nsresult nsGlobalWindowOuter::OpenInternal(
     }
   }
 
-  nsCOMPtr<mozIDOMWindowProxy> domReturn;
+  RefPtr<BrowsingContext> domReturn;
 
   nsCOMPtr<nsIWindowWatcher> wwatch =
       do_GetService(NS_WINDOWWATCHER_CONTRACTID, &rv);
@@ -7277,6 +7275,7 @@ nsresult nsGlobalWindowOuter::OpenInternal(
     // dialog is open.
     AutoPopupStatePusher popupStatePusher(PopupBlocker::openAbused, true);
 
+    nsCOMPtr<mozIDOMWindowProxy> win;
     if (!aCalledNoScript) {
       // We asserted at the top of this function that aNavigate is true for
       // !aCalledNoScript.
@@ -7284,7 +7283,7 @@ nsresult nsGlobalWindowOuter::OpenInternal(
           this, url.IsVoid() ? nullptr : url.get(), name_ptr, options_ptr,
           /* aCalledFromScript = */ true, aDialog, aNavigate, argv,
           isPopupSpamWindow, forceNoOpener, forceNoReferrer, aLoadState,
-          getter_AddRefs(domReturn));
+          getter_AddRefs(win));
     } else {
       // Force a system caller here so that the window watcher won't screw us
       // up.  We do NOT want this case looking at the JS context on the stack
@@ -7304,7 +7303,10 @@ nsresult nsGlobalWindowOuter::OpenInternal(
           this, url.IsVoid() ? nullptr : url.get(), name_ptr, options_ptr,
           /* aCalledFromScript = */ false, aDialog, aNavigate, aExtraArgument,
           isPopupSpamWindow, forceNoOpener, forceNoReferrer, aLoadState,
-          getter_AddRefs(domReturn));
+          getter_AddRefs(win));
+    }
+    if (win) {
+      domReturn = nsPIDOMWindowOuter::From(win)->GetBrowsingContext();
     }
   }
 
@@ -7317,7 +7319,8 @@ nsresult nsGlobalWindowOuter::OpenInternal(
   }
 
   if (domReturn && aDoJSFixups) {
-    nsCOMPtr<nsIDOMChromeWindow> chrome_win(do_QueryInterface(domReturn));
+    nsCOMPtr<nsIDOMChromeWindow> chrome_win(
+        do_QueryInterface(domReturn->GetDOMWindow()));
     if (!chrome_win) {
       // A new non-chrome window was created from a call to
       // window.open() from JavaScript, make sure there's a document in
@@ -7327,12 +7330,14 @@ nsresult nsGlobalWindowOuter::OpenInternal(
       // XXXbz should this just use EnsureInnerWindow()?
 
       // Force document creation.
-      nsCOMPtr<Document> doc = nsPIDOMWindowOuter::From(domReturn)->GetDoc();
-      Unused << doc;
+      if (nsPIDOMWindowOuter* win = domReturn->GetDOMWindow()) {
+        nsCOMPtr<Document> doc = win->GetDoc();
+        Unused << doc;
+      }
     }
   }
 
-  *aReturn = do_AddRef(nsPIDOMWindowOuter::From(domReturn)).take();
+  domReturn.forget(aReturn);
   return NS_OK;
 }
 
diff --git a/dom/base/nsGlobalWindowOuter.h b/dom/base/nsGlobalWindowOuter.h
index 18b82b8c521b..e806dc1ab5b7 100644
--- a/dom/base/nsGlobalWindowOuter.h
+++ b/dom/base/nsGlobalWindowOuter.h
@@ -260,7 +260,8 @@ class nsGlobalWindowOuter final : public mozilla::dom::EventTarget,
       const nsAString& aGroup);
 
   nsresult OpenJS(const nsAString& aUrl, const nsAString& aName,
-                  const nsAString& aOptions, nsPIDOMWindowOuter** _retval);
+                  const nsAString& aOptions,
+                  mozilla::dom::BrowsingContext** _retval);
 
   virtual mozilla::EventListenerManager* GetExistingListenerManager()
       const override;
@@ -565,7 +566,8 @@ class nsGlobalWindowOuter final : public mozilla::dom::EventTarget,
       mozilla::ErrorResult& aError);
   nsresult Open(const nsAString& aUrl, const nsAString& aName,
                 const nsAString& aOptions, nsDocShellLoadState* aLoadState,
-                bool aForceNoOpener, nsPIDOMWindowOuter** _retval) override;
+                bool aForceNoOpener,
+                mozilla::dom::BrowsingContext** _retval) override;
   mozilla::dom::Navigator* GetNavigator() override;
 
 #if defined(MOZ_WIDGET_ANDROID)
@@ -634,7 +636,7 @@ class nsGlobalWindowOuter final : public mozilla::dom::EventTarget,
       mozilla::ErrorResult& aError);
   nsresult OpenDialog(const nsAString& aUrl, const nsAString& aName,
                       const nsAString& aOptions, nsISupports* aExtraArgument,
-                      nsPIDOMWindowOuter** _retval) override;
+                      mozilla::dom::BrowsingContext** _retval) override;
   void UpdateCommands(const nsAString& anAction, mozilla::dom::Selection* aSel,
                       int16_t aReason) override;
 
@@ -760,9 +762,9 @@ class nsGlobalWindowOuter final : public mozilla::dom::EventTarget,
   // Window Control Functions
 
   // Outer windows only.
-  virtual nsresult OpenNoNavigate(const nsAString& aUrl, const nsAString& aName,
-                                  const nsAString& aOptions,
-                                  nsPIDOMWindowOuter** _retval) override;
+  virtual nsresult OpenNoNavigate(
+      const nsAString& aUrl, const nsAString& aName, const nsAString& aOptions,
+      mozilla::dom::BrowsingContext** _retval) override;
 
  private:
   explicit nsGlobalWindowOuter(uint64_t aWindowID);
@@ -822,7 +824,7 @@ class nsGlobalWindowOuter final : public mozilla::dom::EventTarget,
                         bool aDoJSFixups, bool aNavigate, nsIArray* argv,
                         nsISupports* aExtraArgument,
                         nsDocShellLoadState* aLoadState, bool aForceNoOpener,
-                        nsPIDOMWindowOuter** aReturn);
+                        mozilla::dom::BrowsingContext** aReturn);
 
   // Checks that the channel was loaded by the URI currently loaded in aDoc
   static bool SameLoadingURI(Document* aDoc, nsIChannel* aChannel);
diff --git a/dom/base/nsPIDOMWindow.h b/dom/base/nsPIDOMWindow.h
index fde24ef06a01..37973f27f2af 100644
--- a/dom/base/nsPIDOMWindow.h
+++ b/dom/base/nsPIDOMWindow.h
@@ -1010,7 +1010,7 @@ class nsPIDOMWindowOuter : public mozIDOMWindowProxy {
    */
   virtual nsresult OpenNoNavigate(const nsAString& aUrl, const nsAString& aName,
                                   const nsAString& aOptions,
-                                  nsPIDOMWindowOuter** _retval) = 0;
+                                  mozilla::dom::BrowsingContext** _retval) = 0;
 
   /**
    * Fire a popup blocked event on the document.
@@ -1049,11 +1049,11 @@ class nsPIDOMWindowOuter : public mozIDOMWindowProxy {
   virtual nsresult Open(const nsAString& aUrl, const nsAString& aName,
                         const nsAString& aOptions,
                         nsDocShellLoadState* aLoadState, bool aForceNoOpener,
-                        nsPIDOMWindowOuter** _retval) = 0;
+                        mozilla::dom::BrowsingContext** _retval) = 0;
   virtual nsresult OpenDialog(const nsAString& aUrl, const nsAString& aName,
                               const nsAString& aOptions,
                               nsISupports* aExtraArgument,
-                              nsPIDOMWindowOuter** _retval) = 0;
+                              mozilla::dom::BrowsingContext** _retval) = 0;
 
   virtual nsresult GetInnerWidth(int32_t* aWidth) = 0;
   virtual nsresult GetInnerHeight(int32_t* aHeight) = 0;
diff --git a/dom/browser-element/BrowserElementParent.cpp b/dom/browser-element/BrowserElementParent.cpp
index 7b0764dad6e8..7d52d8ce220a 100644
--- a/dom/browser-element/BrowserElementParent.cpp
+++ b/dom/browser-element/BrowserElementParent.cpp
@@ -219,8 +219,8 @@ BrowserElementParent::OpenWindowInProcess(BrowsingContext* aOpenerWindow,
                                           nsIURI* aURI, const nsAString& aName,
                                           const nsACString& aFeatures,
                                           bool aForceNoOpener,
-                                          mozIDOMWindowProxy** aReturnWindow) {
-  *aReturnWindow = nullptr;
+                                          BrowsingContext** aReturnBC) {
+  *aReturnBC = nullptr;
 
   // If we call window.open from an <iframe> inside an <iframe mozbrowser>,
   // it's as though the top-level document inside the <iframe mozbrowser>
@@ -267,11 +267,9 @@ BrowserElementParent::OpenWindowInProcess(BrowsingContext* aOpenerWindow,
   nsCOMPtr<nsIDocShell> docshell = frameLoader->GetDocShell(IgnoreErrors());
   NS_ENSURE_TRUE(docshell, BrowserElementParent::OPEN_WINDOW_IGNORED);
 
-  nsCOMPtr<nsPIDOMWindowOuter> window = docshell->GetWindow();
-  window.forget(aReturnWindow);
+  docshell->GetBrowsingContext(aReturnBC);
 
-  return !!*aReturnWindow ? opened
-                          : BrowserElementParent::OPEN_WINDOW_CANCELLED;
+  return *aReturnBC ? opened : BrowserElementParent::OPEN_WINDOW_CANCELLED;
 }
 
 }  // namespace mozilla
diff --git a/dom/browser-element/BrowserElementParent.h b/dom/browser-element/BrowserElementParent.h
index b1817dfbbe17..0b069b3cbbed 100644
--- a/dom/browser-element/BrowserElementParent.h
+++ b/dom/browser-element/BrowserElementParent.h
@@ -107,7 +107,7 @@ class BrowserElementParent {
   static OpenWindowResult OpenWindowInProcess(
       mozilla::dom::BrowsingContext* aOpenerWindow, nsIURI* aURI,
       const nsAString& aName, const nsACString& aFeatures, bool aForceNoOpener,
-      mozIDOMWindowProxy** aReturnWindow);
+      mozilla::dom::BrowsingContext** aReturnBC);
 
  private:
   static OpenWindowResult DispatchOpenWindowEvent(
diff --git a/dom/clients/manager/ClientOpenWindowUtils.cpp b/dom/clients/manager/ClientOpenWindowUtils.cpp
index f2dd087103b1..c4f7fb4af4d8 100644
--- a/dom/clients/manager/ClientOpenWindowUtils.cpp
+++ b/dom/clients/manager/ClientOpenWindowUtils.cpp
@@ -149,9 +149,8 @@ class WebProgressListener final : public nsIWebProgressListener,
 NS_IMPL_ISUPPORTS(WebProgressListener, nsIWebProgressListener,
                   nsISupportsWeakReference);
 
-nsresult OpenWindow(const ClientOpenWindowArgs& aArgs,
-                    nsPIDOMWindowOuter** aWindow) {
-  MOZ_DIAGNOSTIC_ASSERT(aWindow);
+nsresult OpenWindow(const ClientOpenWindowArgs& aArgs, BrowsingContext** aBC) {
+  MOZ_DIAGNOSTIC_ASSERT(aBC);
 
   // [[1. Let url be the result of parsing url with entry settings object's API
   //   base URL.]]
@@ -226,9 +225,10 @@ nsresult OpenWindow(const ClientOpenWindowArgs& aArgs,
     if (NS_WARN_IF(NS_FAILED(rv))) {
       return rv;
     }
-    nsCOMPtr<nsPIDOMWindowOuter> pwindow = nsPIDOMWindowOuter::From(newWindow);
-    pwindow.forget(aWindow);
-    MOZ_DIAGNOSTIC_ASSERT(*aWindow);
+    RefPtr<BrowsingContext> bc(
+        nsPIDOMWindowOuter::From(newWindow)->GetBrowsingContext());
+    bc.forget(aBC);
+    MOZ_DIAGNOSTIC_ASSERT(*aBC);
     return NS_OK;
   }
 
@@ -254,20 +254,8 @@ nsresult OpenWindow(const ClientOpenWindowArgs& aArgs,
     return NS_ERROR_FAILURE;
   }
 
-  nsCOMPtr<mozIDOMWindowProxy> win;
-  rv = bwin->OpenURI(uri, nullptr, nsIBrowserDOMWindow::OPEN_DEFAULTWINDOW,
-                     nsIBrowserDOMWindow::OPEN_NEW, principal, csp,
-                     getter_AddRefs(win));
-  if (NS_WARN_IF(NS_FAILED(rv))) {
-    return rv;
-  }
-  NS_ENSURE_STATE(win);
-
-  nsCOMPtr<nsPIDOMWindowOuter> pWin = nsPIDOMWindowOuter::From(win);
-  pWin.forget(aWindow);
-  MOZ_DIAGNOSTIC_ASSERT(*aWindow);
-
-  return NS_OK;
+  return bwin->OpenURI(uri, nullptr, nsIBrowserDOMWindow::OPEN_DEFAULTWINDOW,
+                       nsIBrowserDOMWindow::OPEN_NEW, principal, csp, aBC);
 }
 
 void WaitForLoad(const ClientOpenWindowArgs& aArgs,
@@ -390,8 +378,10 @@ RefPtr<ClientOpPromise> ClientOpenWindowInCurrentProcess(
   java::GeckoApp::LaunchOrBringToFront();
 #endif  // MOZ_WIDGET_ANDROID
 
-  nsCOMPtr<nsPIDOMWindowOuter> outerWindow;
-  nsresult rv = OpenWindow(aArgs, getter_AddRefs(outerWindow));
+  RefPtr<BrowsingContext> bc;
+  nsresult rv = OpenWindow(aArgs, getter_AddRefs(bc));
+
+  nsCOMPtr<nsPIDOMWindowOuter> outerWindow(bc->GetDOMWindow());
 
 #ifdef MOZ_WIDGET_ANDROID
   // If we get the NOT_AVAILABLE error that means the browser is still
@@ -402,12 +392,17 @@ RefPtr<ClientOpPromise> ClientOpenWindowInCurrentProcess(
     p->Then(
         SystemGroup::EventTargetFor(TaskCategory::Other), __func__,
         [aArgs, promise](bool aResult) {
-          nsCOMPtr<nsPIDOMWindowOuter> outerWindow;
-          nsresult rv = OpenWindow(aArgs, getter_AddRefs(outerWindow));
+          RefPtr<BrowsingContext> bc;
+          nsresult rv = OpenWindow(aArgs, getter_AddRefs(bc));
           if (NS_WARN_IF(NS_FAILED(rv))) {
             promise->Reject(rv, __func__);
             return;
           }
+          nsCOMPtr<nsPIDOMWindowOuter> outerWindow(bc->GetDOMWindow());
+          if (NS_WARN_IF(!outerWindow)) {
+            promise->Reject(NS_ERROR_FAILURE, __func__);
+            return;
+          }
 
           WaitForLoad(aArgs, outerWindow, promise);
         },
diff --git a/dom/interfaces/base/nsIBrowserDOMWindow.idl b/dom/interfaces/base/nsIBrowserDOMWindow.idl
index 76dbda700a50..7a43be7a48de 100644
--- a/dom/interfaces/base/nsIBrowserDOMWindow.idl
+++ b/dom/interfaces/base/nsIBrowserDOMWindow.idl
@@ -11,6 +11,7 @@ interface nsIURI;
 interface nsIPrincipal;
 interface nsIContentSecurityPolicy;
 interface nsIReferrerInfo;
+webidl BrowsingContext;
 webidl Element;
 
 [scriptable, uuid(e774db14-79ac-4156-a7a3-aa3fd0a22c10)]
@@ -115,7 +116,7 @@ interface nsIBrowserDOMWindow : nsISupports
    * @param aCsp the CSP to use (if any) for the new window.
    * @return the window into which the URI would have been opened.
   */
-  mozIDOMWindowProxy
+  BrowsingContext
   createContentWindow(in nsIURI aURI, in mozIDOMWindowProxy aOpener,
                       in short aWhere, in long aFlags,
                       in nsIPrincipal aTriggeringPrincipal,
@@ -150,7 +151,7 @@ interface nsIBrowserDOMWindow : nsISupports
    * @param aCsp the CSP to be applied to the new load.
    * @return the window into which the URI was opened.
   */
-  mozIDOMWindowProxy
+  BrowsingContext
   openURI(in nsIURI aURI, in mozIDOMWindowProxy aOpener,
           in short aWhere, in long aFlags, in nsIPrincipal aTriggeringPrincipal,
           [optional] in nsIContentSecurityPolicy aCsp);
diff --git a/dom/ipc/BrowserChild.cpp b/dom/ipc/BrowserChild.cpp
index 648bc99089f0..b3ccb0d5ed5e 100644
--- a/dom/ipc/BrowserChild.cpp
+++ b/dom/ipc/BrowserChild.cpp
@@ -55,6 +55,7 @@
 #include "mozilla/Move.h"
 #include "mozilla/PresShell.h"
 #include "mozilla/ProcessHangMonitor.h"
+#include "mozilla/ResultExtensions.h"
 #include "mozilla/ScopeExit.h"
 #include "mozilla/Services.h"
 #include "mozilla/StaticPtr.h"
@@ -903,7 +904,7 @@ BrowserChild::ProvideWindow(mozIDOMWindowProxy* aParent, uint32_t aChromeFlags,
                             const nsAString& aName, const nsACString& aFeatures,
                             bool aForceNoOpener, bool aForceNoReferrer,
                             nsDocShellLoadState* aLoadState, bool* aWindowIsNew,
-                            mozIDOMWindowProxy** aReturn) {
+                            BrowsingContext** aReturn) {
   *aReturn = nullptr;
 
   // If aParent is inside an <iframe mozbrowser> and this isn't a request to
@@ -926,7 +927,14 @@ BrowserChild::ProvideWindow(mozIDOMWindowProxy* aParent, uint32_t aChromeFlags,
     if (openLocation == nsIBrowserDOMWindow::OPEN_CURRENTWINDOW) {
       nsCOMPtr<nsIWebBrowser> browser = do_GetInterface(WebNavigation());
       *aWindowIsNew = false;
-      return browser->GetContentDOMWindow(aReturn);
+
+      nsCOMPtr<mozIDOMWindowProxy> win;
+      MOZ_TRY(browser->GetContentDOMWindow(getter_AddRefs(win)));
+
+      RefPtr<BrowsingContext> bc(
+          nsPIDOMWindowOuter::From(win)->GetBrowsingContext());
+      bc.forget(aReturn);
+      return NS_OK;
     }
   }
 
diff --git a/dom/ipc/ContentChild.cpp b/dom/ipc/ContentChild.cpp
index d6e20b0676e7..dc559f1d5c44 100644
--- a/dom/ipc/ContentChild.cpp
+++ b/dom/ipc/ContentChild.cpp
@@ -771,7 +771,7 @@ ContentChild::ProvideWindow(mozIDOMWindowProxy* aParent, uint32_t aChromeFlags,
                             const nsAString& aName, const nsACString& aFeatures,
                             bool aForceNoOpener, bool aForceNoReferrer,
                             nsDocShellLoadState* aLoadState, bool* aWindowIsNew,
-                            mozIDOMWindowProxy** aReturn) {
+                            BrowsingContext** aReturn) {
   return ProvideWindowCommon(
       nullptr, aParent, false, aChromeFlags, aCalledFromJS, aPositionSpecified,
       aSizeSpecified, aURI, aName, aFeatures, aForceNoOpener, aForceNoReferrer,
@@ -860,7 +860,7 @@ nsresult ContentChild::ProvideWindowCommon(
     bool aSizeSpecified, nsIURI* aURI, const nsAString& aName,
     const nsACString& aFeatures, bool aForceNoOpener, bool aForceNoReferrer,
     nsDocShellLoadState* aLoadState, bool* aWindowIsNew,
-    mozIDOMWindowProxy** aReturn) {
+    BrowsingContext** aReturn) {
   *aReturn = nullptr;
 
   nsAutoPtr<IPCTabContext> ipcContext;
@@ -1104,9 +1104,10 @@ nsresult ContentChild::ProvideWindowCommon(
       newChild->RecvLoadURL(urlToLoad, showInfo);
     }
 
-    nsCOMPtr<mozIDOMWindowProxy> win =
+    nsCOMPtr<nsPIDOMWindowOuter> win =
         do_GetInterface(newChild->WebNavigation());
-    win.forget(aReturn);
+    RefPtr<BrowsingContext> bc(win->GetBrowsingContext());
+    bc.forget(aReturn);
   };
 
   // NOTE: Capturing by reference here is safe, as this function won't return
diff --git a/dom/ipc/ContentChild.h b/dom/ipc/ContentChild.h
index 4544beec53b7..ef01f55208ee 100644
--- a/dom/ipc/ContentChild.h
+++ b/dom/ipc/ContentChild.h
@@ -104,13 +104,15 @@ class ContentChild final : public PContentChild,
     nsCString sourceURL;
   };
 
-  nsresult ProvideWindowCommon(
-      BrowserChild* aTabOpener, mozIDOMWindowProxy* aParent, bool aIframeMoz,
-      uint32_t aChromeFlags, bool aCalledFromJS, bool aPositionSpecified,
-      bool aSizeSpecified, nsIURI* aURI, const nsAString& aName,
-      const nsACString& aFeatures, bool aForceNoOpener, bool aForceNoReferrer,
-      nsDocShellLoadState* aLoadState, bool* aWindowIsNew,
-      mozIDOMWindowProxy** aReturn);
+  nsresult ProvideWindowCommon(BrowserChild* aTabOpener,
+                               mozIDOMWindowProxy* aParent, bool aIframeMoz,
+                               uint32_t aChromeFlags, bool aCalledFromJS,
+                               bool aPositionSpecified, bool aSizeSpecified,
+                               nsIURI* aURI, const nsAString& aName,
+                               const nsACString& aFeatures, bool aForceNoOpener,
+                               bool aForceNoReferrer,
+                               nsDocShellLoadState* aLoadState,
+                               bool* aWindowIsNew, BrowsingContext** aReturn);
 
   bool Init(MessageLoop* aIOLoop, base::ProcessId aParentPid,
             const char* aParentBuildID, IPC::Channel* aChannel,
diff --git a/dom/ipc/ContentParent.cpp b/dom/ipc/ContentParent.cpp
index cd1735b43891..89bb7e1acf66 100644
--- a/dom/ipc/ContentParent.cpp
+++ b/dom/ipc/ContentParent.cpp
@@ -4882,11 +4882,11 @@ mozilla::ipc::IPCResult ContentParent::CommonCreateWindow(
       aResult = NS_ERROR_ABORT;
       return IPC_OK();
     }
-    nsCOMPtr<mozIDOMWindowProxy> win;
+    RefPtr<BrowsingContext> bc;
     aResult = newBrowserDOMWin->OpenURI(
         aURIToLoad, openerWindow, nsIBrowserDOMWindow::OPEN_CURRENTWINDOW,
         nsIBrowserDOMWindow::OPEN_NEW, aTriggeringPrincipal, aCsp,
-        getter_AddRefs(win));
+        getter_AddRefs(bc));
   }
 
   return IPC_OK();
diff --git a/mobile/android/chrome/content/browser.js b/mobile/android/chrome/content/browser.js
index 97695550a5dd..57a3dcdedbd1 100644
--- a/mobile/android/chrome/content/browser.js
+++ b/mobile/android/chrome/content/browser.js
@@ -4224,7 +4224,7 @@ nsBrowserAccess.prototype = {
       aTriggeringPrincipal,
       aCsp
     );
-    return browser && browser.contentWindow;
+    return browser && browser.browsingContext;
   },
 
   createContentWindow: function browser_createContentWindow(
@@ -4243,7 +4243,7 @@ nsBrowserAccess.prototype = {
       aTriggeringPrincipal,
       aCsp
     );
-    return browser && browser.contentWindow;
+    return browser && browser.browsingContext;
   },
 
   openURIInFrame: function browser_openURIInFrame(
diff --git a/mobile/android/modules/geckoview/GeckoViewNavigation.jsm b/mobile/android/modules/geckoview/GeckoViewNavigation.jsm
index ab697b659222..545a73717c47 100644
--- a/mobile/android/modules/geckoview/GeckoViewNavigation.jsm
+++ b/mobile/android/modules/geckoview/GeckoViewNavigation.jsm
@@ -359,7 +359,7 @@ class GeckoViewNavigation extends GeckoViewModule {
       return null;
     }
 
-    return browser.contentWindow;
+    return browser.browsingContext;
   }
 
   // nsIBrowserDOMWindow.
@@ -474,7 +474,7 @@ class GeckoViewNavigation extends GeckoViewModule {
       null,
       null
     );
-    return browser && browser.contentWindow;
+    return browser && browser.browsingContext;
   }
 
   // nsIBrowserDOMWindow.
diff --git a/toolkit/components/printingui/nsPrintProgress.cpp b/toolkit/components/printingui/nsPrintProgress.cpp
index ea9b3c925a5d..92e52915d65a 100644
--- a/toolkit/components/printingui/nsPrintProgress.cpp
+++ b/toolkit/components/printingui/nsPrintProgress.cpp
@@ -5,6 +5,7 @@
 
 #include "nsPrintProgress.h"
 
+#include "mozilla/dom/BrowsingContext.h"
 #include "nsArray.h"
 #include "nsIBaseWindow.h"
 #include "nsIDocShell.h"
@@ -82,12 +83,12 @@ NS_IMETHODIMP nsPrintProgress::OpenProgressDialog(
         nsPIDOMWindowOuter::From(ownerWindow);
 
     // Open the dialog.
-    nsCOMPtr<nsPIDOMWindowOuter> newWindow;
+    RefPtr<mozilla::dom::BrowsingContext> newBC;
 
     rv = piOwnerWindow->OpenDialog(
         NS_ConvertASCIItoUTF16(dialogURL), NS_LITERAL_STRING("_blank"),
         NS_LITERAL_STRING("chrome,titlebar,dependent,centerscreen"), array,
-        getter_AddRefs(newWindow));
+        getter_AddRefs(newBC));
   }
 
   return rv;
diff --git a/toolkit/components/windowcreator/nsIWindowProvider.idl b/toolkit/components/windowcreator/nsIWindowProvider.idl
index f1231ee7612c..20e15d61bae3 100644
--- a/toolkit/components/windowcreator/nsIWindowProvider.idl
+++ b/toolkit/components/windowcreator/nsIWindowProvider.idl
@@ -17,6 +17,7 @@
 class nsDocShellLoadState;
 %}
 
+webidl BrowsingContext;
 interface mozIDOMWindowProxy;
 interface nsIURI;
 native nsDocShellLoadStatePtr(nsDocShellLoadState*);
@@ -97,16 +98,16 @@ interface nsIWindowProvider : nsISupports
    * @see nsIWindowWatcher for more information on aFeatures.
    * @see nsIWebBrowserChrome for more information on aChromeFlags.
    */
-  mozIDOMWindowProxy provideWindow(in mozIDOMWindowProxy aParent,
-                                   in unsigned long aChromeFlags,
-                                   in boolean aCalledFromJS,
-                                   in boolean aPositionSpecified,
-                                   in boolean aSizeSpecified,
-                                   in nsIURI aURI,
-                                   in AString aName,
-                                   in AUTF8String aFeatures,
-                                   in boolean aForceNoOpener,
-                                   in boolean aForceNoReferrer,
-                                   in nsDocShellLoadStatePtr aLoadState,
-                                   out boolean aWindowIsNew);
+  BrowsingContext provideWindow(in mozIDOMWindowProxy aParent,
+                                in unsigned long aChromeFlags,
+                                in boolean aCalledFromJS,
+                                in boolean aPositionSpecified,
+                                in boolean aSizeSpecified,
+                                in nsIURI aURI,
+                                in AString aName,
+                                in AUTF8String aFeatures,
+                                in boolean aForceNoOpener,
+                                in boolean aForceNoReferrer,
+                                in nsDocShellLoadStatePtr aLoadState,
+                                out boolean aWindowIsNew);
 };
diff --git a/toolkit/components/windowwatcher/nsIWindowWatcher.idl b/toolkit/components/windowwatcher/nsIWindowWatcher.idl
index deea268c2a31..d0a46ee9b246 100644
--- a/toolkit/components/windowwatcher/nsIWindowWatcher.idl
+++ b/toolkit/components/windowwatcher/nsIWindowWatcher.idl
@@ -15,7 +15,6 @@ interface nsIWebBrowserChrome;
 interface nsIWindowCreator;
 
 
-
 /**
  * nsIWindowWatcher is the keeper of Gecko/DOM Windows. It maintains
  * a list of open top-level windows, and allows some operations on them.
diff --git a/toolkit/components/windowwatcher/nsWindowWatcher.cpp b/toolkit/components/windowwatcher/nsWindowWatcher.cpp
index f6292f56f037..b2a05ad04483 100644
--- a/toolkit/components/windowwatcher/nsWindowWatcher.cpp
+++ b/toolkit/components/windowwatcher/nsWindowWatcher.cpp
@@ -758,15 +758,14 @@ nsresult nsWindowWatcher::OpenWindowInternal(
       }
 
       if (provider) {
-        nsCOMPtr<mozIDOMWindowProxy> newWindow;
+        RefPtr<BrowsingContext> newBC;
         rv = provider->ProvideWindow(
             aParent, chromeFlags, aCalledFromJS, sizeSpec.PositionSpecified(),
             sizeSpec.SizeSpecified(), uriToLoad, name, features, aForceNoOpener,
-            aForceNoReferrer, aLoadState, &windowIsNew,
-            getter_AddRefs(newWindow));
+            aForceNoReferrer, aLoadState, &windowIsNew, getter_AddRefs(newBC));
 
-        if (NS_SUCCEEDED(rv)) {
-          GetWindowTreeItem(newWindow, getter_AddRefs(newDocShellItem));
+        if (NS_SUCCEEDED(rv) && newBC) {
+          newDocShellItem = newBC->GetDocShell();
           if (windowIsNew && newDocShellItem) {
             // Make sure to stop any loads happening in this window that the
             // window provider might have started.  Otherwise if our caller
@@ -783,7 +782,7 @@ nsresult nsWindowWatcher::OpenWindowInternal(
           if (!windowIsNew && newDocShellItem) {
             nsCOMPtr<nsIDocShell> docShell = do_QueryInterface(newDocShellItem);
             if (!CheckUserContextCompatibility(docShell)) {
-              newWindow = nullptr;
+              newBC = nullptr;
               newDocShellItem = nullptr;
               windowIsNew = false;
             }
diff --git a/xpfe/appshell/nsContentTreeOwner.cpp b/xpfe/appshell/nsContentTreeOwner.cpp
index 7a6c65cfaa77..2b43415bf31b 100644
--- a/xpfe/appshell/nsContentTreeOwner.cpp
+++ b/xpfe/appshell/nsContentTreeOwner.cpp
@@ -704,7 +704,7 @@ nsContentTreeOwner::ProvideWindow(
     bool aPositionSpecified, bool aSizeSpecified, nsIURI* aURI,
     const nsAString& aName, const nsACString& aFeatures, bool aForceNoOpener,
     bool aForceNoReferrer, nsDocShellLoadState* aLoadState, bool* aWindowIsNew,
-    mozIDOMWindowProxy** aReturn) {
+    BrowsingContext** aReturn) {
   NS_ENSURE_ARG_POINTER(aParent);
 
   auto* parentWin = nsPIDOMWindowOuter::From(aParent);