--- a/layout/xul/tree/moz.build
+++ b/layout/xul/tree/moz.build
@@ -5,17 +5,16 @@
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 with Files('**'):
     BUG_COMPONENT = ('Core', 'XUL')
 
 XPIDL_SOURCES += [
     'nsITreeBoxObject.idl',
     'nsITreeColumns.idl',
-    'nsITreeContentView.idl',
     'nsITreeSelection.idl',
     'nsITreeView.idl',
 ]
 
 XPIDL_MODULE = 'layout_xul_tree'
 
 EXPORTS += [
     'nsTreeColFrame.h',

deleted file mode 100644
--- a/layout/xul/tree/nsITreeContentView.idl
+++ /dev/null
@@ -1,22 +0,0 @@
-/* -*- Mode: C++; tab-width: 2; 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"
-
-webidl Element;
-
-[scriptable, builtinclass, uuid(5ef62896-0c0a-41f1-bb3c-44a60f5dfdab)]
-interface nsITreeContentView : nsISupports
-{
-  /**
-   * Retrieve the content item associated with the specified index.
-   */
-  Element getItemAtIndex(in long index);
-
-  /**
-   * Retrieve the index associated with the specified content item.
-   */
-  long getIndexOfItem(in Element item);
-};

--- a/layout/xul/tree/nsTreeContentView.cpp
+++ b/layout/xul/tree/nsTreeContentView.cpp
@@ -111,20 +111,19 @@ NS_IMPL_CYCLE_COLLECTION_WRAPPERCACHE(ns
                                       mRoot,
                                       mBody)
 
 NS_IMPL_CYCLE_COLLECTING_ADDREF(nsTreeContentView)
 NS_IMPL_CYCLE_COLLECTING_RELEASE(nsTreeContentView)
 
 NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(nsTreeContentView)
   NS_INTERFACE_MAP_ENTRY(nsITreeView)
-  NS_INTERFACE_MAP_ENTRY(nsITreeContentView)
   NS_INTERFACE_MAP_ENTRY(nsIDocumentObserver)
   NS_INTERFACE_MAP_ENTRY(nsIMutationObserver)
-  NS_INTERFACE_MAP_ENTRY_AMBIGUOUS(nsISupports, nsITreeContentView)
+  NS_INTERFACE_MAP_ENTRY_AMBIGUOUS(nsISupports, nsITreeView)
   NS_WRAPPERCACHE_INTERFACE_MAP_ENTRY
 NS_INTERFACE_MAP_END
 
 JSObject*
 nsTreeContentView::WrapObject(JSContext* aCx,
                               JS::Handle<JSObject*> aGivenProto)
 {
   return TreeContentViewBinding::Wrap(aCx, this, aGivenProto);
@@ -870,42 +869,22 @@ nsTreeContentView::GetItemAtIndex(int32_
   if (!IsValidRowIndex(aIndex)) {
     aError.Throw(NS_ERROR_INVALID_ARG);
     return nullptr;
   }
 
   return mRows[aIndex]->mContent;
 }
 
-NS_IMETHODIMP
-nsTreeContentView::GetItemAtIndex(int32_t aIndex, Element** _retval)
-{
-  ErrorResult rv;
-  RefPtr<Element> element = GetItemAtIndex(aIndex, rv);
-  if (rv.Failed()) {
-    return rv.StealNSResult();
-  }
-
-  element.forget(_retval);
-  return NS_OK;
-}
-
 int32_t
 nsTreeContentView::GetIndexOfItem(Element* aItem)
 {
   return FindContent(aItem);
 }
 
-NS_IMETHODIMP
-nsTreeContentView::GetIndexOfItem(Element* aItem, int32_t* _retval)
-{
-  *_retval = GetIndexOfItem(aItem);
-  return NS_OK;
-}
-
 void
 nsTreeContentView::AttributeChanged(dom::Element* aElement,
                                     int32_t       aNameSpaceID,
                                     nsAtom*      aAttribute,
                                     int32_t       aModType,
                                     const nsAttrValue* aOldValue)
 {
   // Lots of codepaths under here that do all sorts of stuff, so be safe.

--- a/layout/xul/tree/nsTreeContentView.h
+++ b/layout/xul/tree/nsTreeContentView.h
@@ -7,17 +7,16 @@
 #ifndef nsTreeContentView_h__
 #define nsTreeContentView_h__
 
 #include "nsCycleCollectionParticipant.h"
 #include "nsTArray.h"
 #include "nsStubDocumentObserver.h"
 #include "nsITreeBoxObject.h"
 #include "nsITreeView.h"
-#include "nsITreeContentView.h"
 #include "nsITreeSelection.h"
 #include "mozilla/Attributes.h"
 #include "mozilla/UniquePtr.h"
 
 class nsIDocument;
 class nsSelection;
 class nsTreeColumn;
 class Row;
@@ -28,17 +27,16 @@ class DataTransfer;
 class Element;
 class TreeBoxObject;
 } // namespace dom
 } // namespace mozilla
 
 nsresult NS_NewTreeContentView(nsITreeView** aResult);
 
 class nsTreeContentView final : public nsITreeView,
-                                public nsITreeContentView,
                                 public nsStubDocumentObserver,
                                 public nsWrapperCache
 {
   typedef mozilla::dom::Element Element;
   public:
     nsTreeContentView(void);
 
     NS_DECL_CYCLE_COLLECTING_ISUPPORTS
@@ -114,18 +112,16 @@ class nsTreeContentView final : public n
                              nsTreeColumn& aColumn)
     {
     }
     Element* GetItemAtIndex(int32_t aRow, mozilla::ErrorResult& aError);
     int32_t GetIndexOfItem(Element* aItem);
 
     NS_DECL_NSITREEVIEW
 
-    NS_DECL_NSITREECONTENTVIEW
-
     // nsIDocumentObserver
     NS_DECL_NSIMUTATIONOBSERVER_ATTRIBUTECHANGED
     NS_DECL_NSIMUTATIONOBSERVER_CONTENTAPPENDED
     NS_DECL_NSIMUTATIONOBSERVER_CONTENTINSERTED
     NS_DECL_NSIMUTATIONOBSERVER_CONTENTREMOVED
     NS_DECL_NSIMUTATIONOBSERVER_NODEWILLBEDESTROYED
 
     static bool CanTrustTreeSelection(nsISupports* aValue);

--- a/toolkit/content/widgets/tree.xml
+++ b/toolkit/content/widgets/tree.xml
@@ -79,17 +79,17 @@
                 onget="return this.view ? this.view.selection.currentIndex: - 1;"
                 onset="if (this.view) return this.view.selection.currentIndex = val; return val;"/>
 
       <property name="treeBoxObject"
                 onget="return this.boxObject;"
                 readonly="true"/>
 # contentView is obsolete (see bug 202391)
       <property name="contentView"
-                onget="return this.view; /*.QueryInterface(Components.interfaces.nsITreeContentView)*/"
+                onget="return this.view;"
                 readonly="true"/>
 # builderView is obsolete (see bug 202393)
       <property name="builderView"
                 onget="return this.view; /*.QueryInterface(Components.interfaces.nsIXULTreeBuilder)*/"
                 readonly="true"/>
       <field name="pageUpOrDownMovesSelection">
         !/Mac/.test(navigator.platform)
       </field>