--- a/docshell/base/moz.build
+++ b/docshell/base/moz.build
@@ -34,17 +34,16 @@ with Files('nsIScrollObserver.*'):
 DIRS += [
     'timeline',
 ]
 
 XPIDL_SOURCES += [
     'nsCDefaultURIFixup.idl',
     'nsIClipboardCommands.idl',
     'nsIContentViewer.idl',
-    'nsIContentViewerContainer.idl',
     'nsIContentViewerEdit.idl',
     'nsIDocCharset.idl',
     'nsIDocShell.idl',
     'nsIDocShellLoadInfo.idl',
     'nsIDocShellTreeItem.idl',
     'nsIDocShellTreeOwner.idl',
     'nsIDocumentLoaderFactory.idl',
     'nsIDownloadHistory.idl',

--- a/docshell/base/nsDocShell.cpp
+++ b/docshell/base/nsDocShell.cpp
@@ -508,17 +508,16 @@ NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(
   NS_INTERFACE_MAP_ENTRY(nsIWebNavigation)
   NS_INTERFACE_MAP_ENTRY(nsIBaseWindow)
   NS_INTERFACE_MAP_ENTRY(nsIScrollable)
   NS_INTERFACE_MAP_ENTRY(nsITextScroll)
   NS_INTERFACE_MAP_ENTRY(nsIDocCharset)
   NS_INTERFACE_MAP_ENTRY(nsIRefreshURI)
   NS_INTERFACE_MAP_ENTRY(nsIWebProgressListener)
   NS_INTERFACE_MAP_ENTRY(nsISupportsWeakReference)
-  NS_INTERFACE_MAP_ENTRY(nsIContentViewerContainer)
   NS_INTERFACE_MAP_ENTRY(nsIWebPageDescriptor)
   NS_INTERFACE_MAP_ENTRY(nsIAuthPromptProvider)
   NS_INTERFACE_MAP_ENTRY(nsILoadContext)
   NS_INTERFACE_MAP_ENTRY(nsIWebShellServices)
   NS_INTERFACE_MAP_ENTRY(nsILinkHandler)
   NS_INTERFACE_MAP_ENTRY(nsIClipboardCommands)
   NS_INTERFACE_MAP_ENTRY(nsIDOMStorageManager)
   NS_INTERFACE_MAP_ENTRY(nsINetworkInterceptController)

--- a/docshell/base/nsDocShell.h
+++ b/docshell/base/nsDocShell.h
@@ -15,17 +15,16 @@
 #include "mozilla/UniquePtr.h"
 #include "mozilla/WeakPtr.h"
 
 #include "mozilla/dom/ProfileTimelineMarkerBinding.h"
 
 #include "nsIAuthPromptProvider.h"
 #include "nsIBaseWindow.h"
 #include "nsIClipboardCommands.h"
-#include "nsIContentViewerContainer.h"
 #include "nsIDeprecationWarner.h"
 #include "nsIDocCharset.h"
 #include "nsIDocShell.h"
 #include "nsIDocShellLoadInfo.h"
 #include "nsIDocShellTreeItem.h"
 #include "nsIDOMStorageManager.h"
 #include "nsIInterfaceRequestor.h"
 #include "nsILinkHandler.h"
@@ -122,17 +121,16 @@ enum eCharsetReloadState
 class nsDocShell final
   : public nsDocLoader
   , public nsIDocShell
   , public nsIWebNavigation
   , public nsIBaseWindow
   , public nsIScrollable
   , public nsITextScroll
   , public nsIDocCharset
-  , public nsIContentViewerContainer
   , public nsIRefreshURI
   , public nsIWebProgressListener
   , public nsIWebPageDescriptor
   , public nsIAuthPromptProvider
   , public nsILoadContext
   , public nsIWebShellServices
   , public nsILinkHandler
   , public nsIClipboardCommands
@@ -178,17 +176,16 @@ public:
   NS_DECL_NSIWEBNAVIGATION
   NS_DECL_NSIBASEWINDOW
   NS_DECL_NSISCROLLABLE
   NS_DECL_NSITEXTSCROLL
   NS_DECL_NSIDOCCHARSET
   NS_DECL_NSIINTERFACEREQUESTOR
   NS_DECL_NSIWEBPROGRESSLISTENER
   NS_DECL_NSIREFRESHURI
-  NS_DECL_NSICONTENTVIEWERCONTAINER
   NS_DECL_NSIWEBPAGEDESCRIPTOR
   NS_DECL_NSIAUTHPROMPTPROVIDER
   NS_DECL_NSICLIPBOARDCOMMANDS
   NS_DECL_NSIWEBSHELLSERVICES
   NS_DECL_NSINETWORKINTERCEPTCONTROLLER
   NS_DECL_NSIDEPRECATIONWARNER
 
   NS_FORWARD_SAFE_NSIDOMSTORAGEMANAGER(TopSessionStorageManager())

deleted file mode 100644
--- a/docshell/base/nsIContentViewerContainer.idl
+++ /dev/null
@@ -1,13 +0,0 @@
-/* -*- Mode: IDL; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*-
- *
- * This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-#include "nsISupports.idl"
-
-interface nsIContentViewer;
-
-[scriptable, uuid(ea2ce7a0-5c3d-11d4-90c2-0050041caf44)]
-interface nsIContentViewerContainer : nsISupports {
-};

--- a/dom/html/nsHTMLDocument.cpp
+++ b/dom/html/nsHTMLDocument.cpp
@@ -27,17 +27,16 @@
 #include "nsIDOMElement.h"
 #include "nsPIDOMWindow.h"
 #include "nsDOMString.h"
 #include "nsIStreamListener.h"
 #include "nsIURI.h"
 #include "nsIIOService.h"
 #include "nsNetUtil.h"
 #include "nsIPrivateBrowsingChannel.h"
-#include "nsIContentViewerContainer.h"
 #include "nsIContentViewer.h"
 #include "nsDocShell.h"
 #include "nsDocShellLoadTypes.h"
 #include "nsIWebNavigation.h"
 #include "nsIBaseWindow.h"
 #include "nsIWebShellServices.h"
 #include "nsIScriptContext.h"
 #include "nsIXPConnect.h"

--- a/dom/xml/XMLDocument.cpp
+++ b/dom/xml/XMLDocument.cpp
@@ -6,17 +6,16 @@
 
 
 #include "mozilla/dom/XMLDocument.h"
 #include "nsParserCIID.h"
 #include "nsCharsetSource.h"
 #include "nsIXMLContentSink.h"
 #include "nsPresContext.h"
 #include "nsIContent.h"
-#include "nsIContentViewerContainer.h"
 #include "nsIContentViewer.h"
 #include "nsIDocShell.h"
 #include "nsHTMLParts.h"
 #include "nsIComponentManager.h"
 #include "nsIDOMElement.h"
 #include "nsIBaseWindow.h"
 #include "nsIDOMWindow.h"
 #include "nsIDOMDocumentType.h"

--- a/layout/printing/nsPrintJob.cpp
+++ b/layout/printing/nsPrintJob.cpp
@@ -101,17 +101,16 @@ static const char kPrintingPromptService
 #include "nsIInterfaceRequestor.h"
 #include "nsIInterfaceRequestorUtils.h"
 #include "nsIDocShellTreeOwner.h"
 #include "nsIWebBrowserChrome.h"
 #include "nsIBaseWindow.h"
 #include "nsILayoutHistoryState.h"
 #include "nsFrameManager.h"
 #include "mozilla/ReflowInput.h"
-#include "nsIContentViewerContainer.h"
 #include "nsIContentViewer.h"
 #include "nsIDocumentViewerPrint.h"
 
 #include "nsFocusManager.h"
 #include "nsRange.h"
 #include "nsCDefaultURIFixup.h"
 #include "nsIURIFixup.h"
 #include "mozilla/dom/Element.h"