diff --git a/dom/base/Attr.cpp b/dom/base/Attr.cpp
index 1a9171ee4cf2..aa262c45d0fe 100644
--- a/dom/base/Attr.cpp
+++ b/dom/base/Attr.cpp
@@ -289,18 +289,6 @@ Attr::InsertChildBefore(nsIContent* aKid, nsIContent* aBeforeThis,
   return NS_ERROR_NOT_IMPLEMENTED;
 }
 
-nsresult
-Attr::InsertChildAt_Deprecated(nsIContent* aKid, uint32_t aIndex,
-                               bool aNotify)
-{
-  return NS_ERROR_NOT_IMPLEMENTED;
-}
-
-void
-Attr::RemoveChildAt_Deprecated(uint32_t aIndex, bool aNotify)
-{
-}
-
 void
 Attr::RemoveChildNode(nsIContent* aKid, bool aNotify)
 {
diff --git a/dom/base/Attr.h b/dom/base/Attr.h
index d0040506b04e..2d73ec085719 100644
--- a/dom/base/Attr.h
+++ b/dom/base/Attr.h
@@ -63,9 +63,6 @@ public:
   virtual int32_t ComputeIndexOf(const nsINode* aPossibleChild) const override;
   virtual nsresult InsertChildBefore(nsIContent* aKid, nsIContent* aBeforeThis,
                                      bool aNotify) override;
-  virtual nsresult InsertChildAt_Deprecated(nsIContent* aKid, uint32_t aIndex,
-                                            bool aNotify) override;
-  virtual void RemoveChildAt_Deprecated(uint32_t aIndex, bool aNotify) override;
   virtual void RemoveChildNode(nsIContent* aKid, bool aNotify) override;
   virtual nsresult Clone(mozilla::dom::NodeInfo *aNodeInfo, nsINode **aResult,
                          bool aPreallocateChildren) const override;
diff --git a/dom/base/CharacterData.cpp b/dom/base/CharacterData.cpp
index 806e6653731e..c66a8294744c 100644
--- a/dom/base/CharacterData.cpp
+++ b/dom/base/CharacterData.cpp
@@ -634,19 +634,6 @@ CharacterData::InsertChildBefore(nsIContent* aKid,
   return NS_OK;
 }
 
-nsresult
-CharacterData::InsertChildAt_Deprecated(nsIContent* aKid,
-                                        uint32_t aIndex,
-                                        bool aNotify)
-{
-  return NS_OK;
-}
-
-void
-CharacterData::RemoveChildAt_Deprecated(uint32_t aIndex, bool aNotify)
-{
-}
-
 void
 CharacterData::RemoveChildNode(nsIContent* aKid, bool aNotify)
 {
diff --git a/dom/base/CharacterData.h b/dom/base/CharacterData.h
index 12f9d13b443e..f9f8027c2ff7 100644
--- a/dom/base/CharacterData.h
+++ b/dom/base/CharacterData.h
@@ -105,9 +105,6 @@ public:
   virtual int32_t ComputeIndexOf(const nsINode* aPossibleChild) const override;
   virtual nsresult InsertChildBefore(nsIContent* aKid, nsIContent* aBeforeThis,
                                      bool aNotify) override;
-  virtual nsresult InsertChildAt_Deprecated(nsIContent* aKid, uint32_t aIndex,
-                                            bool aNotify) override;
-  virtual void RemoveChildAt_Deprecated(uint32_t aIndex, bool aNotify) override;
   virtual void RemoveChildNode(nsIContent* aKid, bool aNotify) override;
   virtual void GetTextContentInternal(nsAString& aTextContent,
                                       OOMReporter& aError) override
diff --git a/dom/base/FragmentOrElement.cpp b/dom/base/FragmentOrElement.cpp
index 369ae38009a0..737cdb4f7088 100644
--- a/dom/base/FragmentOrElement.cpp
+++ b/dom/base/FragmentOrElement.cpp
@@ -1225,27 +1225,6 @@ FragmentOrElement::InsertChildBefore(nsIContent* aKid,
   return doInsertChildAt(aKid, index, aNotify, mAttrsAndChildren);
 }
 
-nsresult
-FragmentOrElement::InsertChildAt_Deprecated(nsIContent* aKid,
-                                            uint32_t aIndex,
-                                            bool aNotify)
-{
-  MOZ_ASSERT(aKid, "null ptr");
-
-  return doInsertChildAt(aKid, aIndex, aNotify, mAttrsAndChildren);
-}
-
-void
-FragmentOrElement::RemoveChildAt_Deprecated(uint32_t aIndex, bool aNotify)
-{
-  nsCOMPtr<nsIContent> oldKid = mAttrsAndChildren.GetSafeChildAt(aIndex);
-  NS_ASSERTION(oldKid == GetChildAt_Deprecated(aIndex), "Unexpected child in RemoveChildAt_Deprecated");
-
-  if (oldKid) {
-    doRemoveChildAt(aIndex, aNotify, oldKid, mAttrsAndChildren);
-  }
-}
-
 void
 FragmentOrElement::RemoveChildNode(nsIContent* aKid, bool aNotify)
 {
diff --git a/dom/base/FragmentOrElement.h b/dom/base/FragmentOrElement.h
index 03795a2e6c61..6e35b5a33eee 100644
--- a/dom/base/FragmentOrElement.h
+++ b/dom/base/FragmentOrElement.h
@@ -98,9 +98,6 @@ public:
   virtual int32_t ComputeIndexOf(const nsINode* aPossibleChild) const override;
   virtual nsresult InsertChildBefore(nsIContent* aKid, nsIContent* aBeforeThis,
                                      bool aNotify) override;
-  virtual nsresult InsertChildAt_Deprecated(nsIContent* aKid, uint32_t aIndex,
-                                            bool aNotify) override;
-  virtual void RemoveChildAt_Deprecated(uint32_t aIndex, bool aNotify) override;
   virtual void RemoveChildNode(nsIContent* aKid, bool aNotify) override;
   virtual void GetTextContentInternal(nsAString& aTextContent,
                                       mozilla::OOMReporter& aError) override;
diff --git a/dom/base/nsDocument.cpp b/dom/base/nsDocument.cpp
index b6409763b873..d3f455237972 100644
--- a/dom/base/nsDocument.cpp
+++ b/dom/base/nsDocument.cpp
@@ -4109,46 +4109,6 @@ nsIDocument::InsertChildBefore(nsIContent* aKid,
   return doInsertChildAt(aKid, index, aNotify, mChildren);
 }
 
-nsresult
-nsIDocument::InsertChildAt_Deprecated(nsIContent* aKid,
-                                      uint32_t aIndex,
-                                      bool aNotify)
-{
-  if (aKid->IsElement() && GetRootElement()) {
-    NS_WARNING("Inserting root element when we already have one");
-    return NS_ERROR_DOM_HIERARCHY_REQUEST_ERR;
-  }
-
-  return doInsertChildAt(aKid, aIndex, aNotify, mChildren);
-}
-
-void
-nsIDocument::RemoveChildAt_Deprecated(uint32_t aIndex, bool aNotify)
-{
-  nsCOMPtr<nsIContent> oldKid = GetChildAt_Deprecated(aIndex);
-  if (!oldKid) {
-    return;
-  }
-
-  if (oldKid->IsElement()) {
-    // Destroy the link map up front before we mess with the child list.
-    DestroyElementMaps();
-  }
-
-  // Preemptively clear mCachedRootElement, since we may be about to remove it
-  // from our child list, and we don't want to return this maybe-obsolete value
-  // from any GetRootElement() calls that happen inside of doRemoveChildAt().
-  // (NOTE: for this to be useful, doRemoveChildAt() must NOT trigger any
-  // GetRootElement() calls until after it's removed the child from mChildren.
-  // Any call before that point would restore this soon-to-be-obsolete cached
-  // answer, and our clearing here would be fruitless.)
-  mCachedRootElement = nullptr;
-  doRemoveChildAt(aIndex, aNotify, oldKid, mChildren);
-  MOZ_ASSERT(mCachedRootElement != oldKid,
-             "Stale pointer in mCachedRootElement, after we tried to clear it "
-             "(maybe somebody called GetRootElement() too early?)");
-}
-
 void
 nsIDocument::RemoveChildNode(nsIContent* aKid, bool aNotify)
 {
diff --git a/dom/base/nsIDocument.h b/dom/base/nsIDocument.h
index cb02e9be82f9..fbb209f51264 100644
--- a/dom/base/nsIDocument.h
+++ b/dom/base/nsIDocument.h
@@ -548,9 +548,6 @@ public:
 
   nsresult InsertChildBefore(nsIContent* aKid, nsIContent* aBeforeThis,
                              bool aNotify) override;
-  nsresult InsertChildAt_Deprecated(nsIContent* aKid, uint32_t aIndex,
-                                    bool aNotify) override;
-  void RemoveChildAt_Deprecated(uint32_t aIndex, bool aNotify) final;
   void RemoveChildNode(nsIContent* aKid, bool aNotify) final;
   nsresult Clone(mozilla::dom::NodeInfo* aNodeInfo,
                  nsINode **aResult,
diff --git a/dom/base/nsINode.cpp b/dom/base/nsINode.cpp
index 766e6e27ed80..c8ea6f6069b4 100644
--- a/dom/base/nsINode.cpp
+++ b/dom/base/nsINode.cpp
@@ -533,7 +533,7 @@ nsINode::GetNodeValueInternal(nsAString& aNodeValue)
 nsINode*
 nsINode::RemoveChild(nsINode& aOldChild, ErrorResult& aError)
 {
-  if (IsCharacterData()) {
+  if (!aOldChild.IsContent()) {
     // aOldChild can't be one of our children.
     aError.Throw(NS_ERROR_DOM_NOT_FOUND_ERR);
     return nullptr;
@@ -543,14 +543,16 @@ nsINode::RemoveChild(nsINode& aOldChild, ErrorResult& aError)
     nsContentUtils::MaybeFireNodeRemoved(&aOldChild, this);
   }
 
-  int32_t index = ComputeIndexOf(&aOldChild);
-  if (index == -1) {
+  // Check again, we may not be the child's parent anymore.
+  // Can be triggered by dom/base/crashtests/293388-1.html
+  if (aOldChild.AsContent()->IsRootOfAnonymousSubtree() ||
+      aOldChild.GetParentNode() != this) {
     // aOldChild isn't one of our children.
     aError.Throw(NS_ERROR_DOM_NOT_FOUND_ERR);
     return nullptr;
   }
 
-  RemoveChildAt_Deprecated(index, true);
+  RemoveChildNode(aOldChild.AsContent(), true);
   return &aOldChild;
 }
 
@@ -640,7 +642,7 @@ nsINode::Normalize()
                  "Should always have a parent unless "
                  "mutation events messed us up");
     if (parent) {
-      parent->RemoveChildAt_Deprecated(parent->ComputeIndexOf(node), true);
+      parent->RemoveChildNode(node, true);
     }
   }
 }
@@ -1997,11 +1999,12 @@ nsINode::ReplaceOrInsertBefore(bool aReplace, nsINode* aNewChild,
   }
 
   // Record the node to insert before, if any
-  nsINode* nodeToInsertBefore;
+  nsIContent* nodeToInsertBefore;
   if (aReplace) {
     nodeToInsertBefore = aRefChild->GetNextSibling();
   } else {
-    nodeToInsertBefore = aRefChild;
+    // Since aRefChild is our child, it must be an nsIContent object.
+    nodeToInsertBefore = aRefChild ? aRefChild->AsContent() : nullptr;
   }
   if (nodeToInsertBefore == aNewChild) {
     // We're going to remove aNewChild from its parent, so use its next sibling
@@ -2015,14 +2018,6 @@ nsINode::ReplaceOrInsertBefore(bool aReplace, nsINode* aNewChild,
   nsIContent* newContent = aNewChild->AsContent();
   nsCOMPtr<nsINode> oldParent = newContent->GetParentNode();
   if (oldParent) {
-    int32_t removeIndex = oldParent->ComputeIndexOf(newContent);
-    if (removeIndex < 0) {
-      // newContent is anonymous.  We can't deal with this, so just bail
-      NS_ERROR("How come our flags didn't catch this?");
-      aError.Throw(NS_ERROR_DOM_NOT_SUPPORTED_ERR);
-      return nullptr;
-    }
-
     // Hold a strong ref to nodeToInsertBefore across the removal of newContent
     nsCOMPtr<nsINode> kungFuDeathGrip = nodeToInsertBefore;
 
@@ -2034,11 +2029,14 @@ nsINode::ReplaceOrInsertBefore(bool aReplace, nsINode* aNewChild,
     {
       mozAutoDocUpdate batch(newContent->GetComposedDoc(), true);
       nsAutoMutationBatch mb(oldParent, true, true);
-      oldParent->RemoveChildAt_Deprecated(removeIndex, true);
+      // ScriptBlocker ensures previous and next stay alive.
+      nsIContent* previous = aNewChild->GetPreviousSibling();
+      nsIContent* next = aNewChild->GetNextSibling();
+      oldParent->RemoveChildNode(aNewChild->AsContent(), true);
       if (nsAutoMutationBatch::GetCurrentBatch() == &mb) {
         mb.RemovalDone();
-        mb.SetPrevSibling(oldParent->GetChildAt_Deprecated(removeIndex - 1));
-        mb.SetNextSibling(oldParent->GetChildAt_Deprecated(removeIndex));
+        mb.SetPrevSibling(previous);
+        mb.SetNextSibling(next);
       }
     }
 
@@ -2077,7 +2075,7 @@ nsINode::ReplaceOrInsertBefore(bool aReplace, nsINode* aNewChild,
         if (aReplace) {
           nodeToInsertBefore = aRefChild->GetNextSibling();
         } else {
-          nodeToInsertBefore = aRefChild;
+          nodeToInsertBefore = aRefChild ? aRefChild->AsContent() : nullptr;
         }
       }
     }
@@ -2112,8 +2110,8 @@ nsINode::ReplaceOrInsertBefore(bool aReplace, nsINode* aNewChild,
       mozAutoDocUpdate batch(newContent->GetComposedDoc(), true);
       nsAutoMutationBatch mb(newContent, false, true);
 
-      for (uint32_t i = count; i > 0;) {
-        newContent->RemoveChildAt_Deprecated(--i, true);
+      while (newContent->HasChildren()) {
+        newContent->RemoveChildNode(newContent->GetLastChild(), true);
       }
     }
 
@@ -2151,7 +2149,8 @@ nsINode::ReplaceOrInsertBefore(bool aReplace, nsINode* aNewChild,
       if (aReplace) {
         nodeToInsertBefore = aRefChild->GetNextSibling();
       } else {
-        nodeToInsertBefore = aRefChild;
+        // If aRefChild has 'this' as a parent, it must be an nsIContent.
+        nodeToInsertBefore = aRefChild ? aRefChild->AsContent() : nullptr;
       }
 
       // And verify that newContent is still allowed as our child.  Sadly, we
@@ -2182,23 +2181,6 @@ nsINode::ReplaceOrInsertBefore(bool aReplace, nsINode* aNewChild,
   mozAutoDocUpdate batch(GetComposedDoc(), true);
   nsAutoMutationBatch mb;
 
-  // Figure out which index we want to insert at.  Note that we use
-  // nodeToInsertBefore to determine this, because it's possible that
-  // aRefChild == aNewChild, in which case we just removed it from the
-  // parent list.
-  int32_t insPos;
-  if (nodeToInsertBefore) {
-    insPos = ComputeIndexOf(nodeToInsertBefore);
-    if (insPos < 0) {
-      // XXXbz How the heck would _that_ happen, exactly?
-      aError.Throw(NS_ERROR_DOM_NOT_FOUND_ERR);
-      return nullptr;
-    }
-  }
-  else {
-    insPos = GetChildCount();
-  }
-
   // If we're replacing and we haven't removed aRefChild yet, do so now
   if (aReplace && aRefChild != aNewChild) {
     mb.Init(this, true, true);
@@ -2208,11 +2190,11 @@ nsINode::ReplaceOrInsertBefore(bool aReplace, nsINode* aNewChild,
     NS_ASSERTION(aRefChild->GetNextSibling() == nodeToInsertBefore,
                  "Unexpected nodeToInsertBefore");
 
-    // An since nodeToInsertBefore is at index insPos, we want to remove
-    // at the previous index.
-    NS_ASSERTION(insPos >= 1, "insPos too small");
-    RemoveChildAt_Deprecated(insPos-1, true);
-    --insPos;
+    nsIContent* toBeRemoved = nodeToInsertBefore ?
+      nodeToInsertBefore->GetPreviousSibling() : GetLastChild();
+    MOZ_ASSERT(toBeRemoved);
+
+    RemoveChildNode(toBeRemoved, true);
   }
 
   // Move new child over to our document if needed. Do this after removing
@@ -2246,8 +2228,9 @@ nsINode::ReplaceOrInsertBefore(bool aReplace, nsINode* aNewChild,
     nsAutoMutationBatch* mutationBatch = nsAutoMutationBatch::GetCurrentBatch();
     if (mutationBatch) {
       mutationBatch->RemovalDone();
-      mutationBatch->SetPrevSibling(GetChildAt_Deprecated(insPos - 1));
-      mutationBatch->SetNextSibling(GetChildAt_Deprecated(insPos));
+      mutationBatch->SetPrevSibling(nodeToInsertBefore ?
+        nodeToInsertBefore->GetPreviousSibling() : GetLastChild());
+      mutationBatch->SetNextSibling(nodeToInsertBefore);
     }
 
     uint32_t count = fragChildren->Length();
@@ -2255,16 +2238,16 @@ nsINode::ReplaceOrInsertBefore(bool aReplace, nsINode* aNewChild,
       return result;
     }
 
-    bool appending = !IsDocument() && uint32_t(insPos) == GetChildCount();
+    bool appending = !IsDocument() && !nodeToInsertBefore;
     nsIContent* firstInsertedContent = fragChildren->ElementAt(0);
 
     // Iterate through the fragment's children, and insert them in the new
     // parent
-    for (uint32_t i = 0; i < count; ++i, ++insPos) {
+    for (uint32_t i = 0; i < count; ++i) {
       // XXXbz how come no reparenting here?  That seems odd...
       // Insert the child.
-      aError = InsertChildAt_Deprecated(fragChildren->ElementAt(i), insPos,
-                                        !appending);
+      aError = InsertChildBefore(fragChildren->ElementAt(i), nodeToInsertBefore,
+                                 !appending);
       if (aError.Failed()) {
         // Make sure to notify on any children that we did succeed to insert
         if (appending && i != 0) {
@@ -2300,13 +2283,13 @@ nsINode::ReplaceOrInsertBefore(bool aReplace, nsINode* aNewChild,
     //       We need to reparent here for nodes for which the parent of their
     //       wrapper is not the wrapper for their ownerDocument (XUL elements,
     //       form controls, ...). Also applies in the fragment code above.
-
     if (nsAutoMutationBatch::GetCurrentBatch() == &mb) {
       mb.RemovalDone();
-      mb.SetPrevSibling(GetChildAt_Deprecated(insPos - 1));
-      mb.SetNextSibling(GetChildAt_Deprecated(insPos));
+      mb.SetPrevSibling(nodeToInsertBefore ?
+                        nodeToInsertBefore->GetPreviousSibling() : GetLastChild());
+      mb.SetNextSibling(nodeToInsertBefore);
     }
-    aError = InsertChildAt_Deprecated(newContent, insPos, true);
+    aError = InsertChildBefore(newContent, nodeToInsertBefore, true);
     if (aError.Failed()) {
       return nullptr;
     }
diff --git a/dom/base/nsINode.h b/dom/base/nsINode.h
index e7fdc9e856f9..02c9e01b273e 100644
--- a/dom/base/nsINode.h
+++ b/dom/base/nsINode.h
@@ -821,29 +821,6 @@ public:
   virtual nsresult InsertChildBefore(nsIContent* aKid, nsIContent* aBeforeThis,
                                      bool aNotify) = 0;
 
-  /**
-   * Insert a content node at a particular index.  This method handles calling
-   * BindToTree on the child appropriately.
-   *
-   * @param aKid the content to insert
-   * @param aIndex the index it is being inserted at (the index it will have
-   *        after it is inserted)
-   * @param aNotify whether to notify the document (current document for
-   *        nsIContent, and |this| for nsIDocument) that the insert has
-   *        occurred
-   *
-   * @throws NS_ERROR_DOM_HIERARCHY_REQUEST_ERR if one attempts to have more
-   * than one element node as a child of a document.  Doing this will also
-   * assert -- you shouldn't be doing it!  Check with
-   * nsIDocument::GetRootElement() first if you're not sure.  Apart from this
-   * one constraint, this doesn't do any checking on whether aKid is a valid
-   * child of |this|.
-   *
-   * @throws NS_ERROR_OUT_OF_MEMORY in some cases (from BindToTree).
-   */
-  virtual nsresult InsertChildAt_Deprecated(nsIContent* aKid, uint32_t aIndex,
-                                            bool aNotify) = 0;
-
   /**
    * Append a content node to the end of the child list.  This method handles
    * calling BindToTree on the child appropriately.
@@ -864,25 +841,9 @@ public:
    */
   nsresult AppendChildTo(nsIContent* aKid, bool aNotify)
   {
-    return InsertChildAt_Deprecated(aKid, GetChildCount(), aNotify);
+    return InsertChildBefore(aKid, nullptr, aNotify);
   }
 
-  /**
-   * NOTE: this function is going to be removed soon (hopefully!) Don't use it
-   * in new code.
-   *
-   * Remove a child from this node.  This method handles calling UnbindFromTree
-   * on the child appropriately.
-   *
-   * @param aIndex the index of the child to remove
-   * @param aNotify whether to notify the document (current document for
-   *        nsIContent, and |this| for nsIDocument) that the remove has
-   *        occurred
-   *
-   * Note: If there is no child at aIndex, this method will simply do nothing.
-   */
-  virtual void RemoveChildAt_Deprecated(uint32_t aIndex, bool aNotify) = 0;
-
   /**
    * Remove a child from this node.  This method handles calling UnbindFromTree
    * on the child appropriately.
diff --git a/dom/html/HTMLFieldSetElement.cpp b/dom/html/HTMLFieldSetElement.cpp
index fd50146f5e28..152881bc76d2 100644
--- a/dom/html/HTMLFieldSetElement.cpp
+++ b/dom/html/HTMLFieldSetElement.cpp
@@ -171,64 +171,6 @@ HTMLFieldSetElement::InsertChildBefore(nsIContent* aChild,
   return rv;
 }
 
-nsresult
-HTMLFieldSetElement::InsertChildAt_Deprecated(nsIContent* aChild,
-                                              uint32_t aIndex,
-                                              bool aNotify)
-{
-  bool firstLegendHasChanged = false;
-
-  if (aChild->IsHTMLElement(nsGkAtoms::legend)) {
-    if (!mFirstLegend) {
-      mFirstLegend = aChild;
-      // We do not want to notify the first time mFirstElement is set.
-    } else {
-      // If mFirstLegend is before aIndex, we do not change it.
-      // Otherwise, mFirstLegend is now aChild.
-      if (int32_t(aIndex) <= ComputeIndexOf(mFirstLegend)) {
-        mFirstLegend = aChild;
-        firstLegendHasChanged = true;
-      }
-    }
-  }
-
-  nsresult rv =
-    nsGenericHTMLFormElement::InsertChildAt_Deprecated(aChild, aIndex, aNotify);
-  NS_ENSURE_SUCCESS(rv, rv);
-
-  if (firstLegendHasChanged) {
-    NotifyElementsForFirstLegendChange(aNotify);
-  }
-
-  return rv;
-}
-
-void
-HTMLFieldSetElement::RemoveChildAt_Deprecated(uint32_t aIndex, bool aNotify)
-{
-  bool firstLegendHasChanged = false;
-
-  if (mFirstLegend && (GetChildAt_Deprecated(aIndex) == mFirstLegend)) {
-    // If we are removing the first legend we have to found another one.
-    nsIContent* child = mFirstLegend->GetNextSibling();
-    mFirstLegend = nullptr;
-    firstLegendHasChanged = true;
-
-    for (; child; child = child->GetNextSibling()) {
-      if (child->IsHTMLElement(nsGkAtoms::legend)) {
-        mFirstLegend = child;
-        break;
-      }
-    }
-  }
-
-  nsGenericHTMLFormElement::RemoveChildAt_Deprecated(aIndex, aNotify);
-
-  if (firstLegendHasChanged) {
-    NotifyElementsForFirstLegendChange(aNotify);
-  }
-}
-
 void
 HTMLFieldSetElement::RemoveChildNode(nsIContent* aKid, bool aNotify)
 {
diff --git a/dom/html/HTMLFieldSetElement.h b/dom/html/HTMLFieldSetElement.h
index a9d98608aa24..5146219a4506 100644
--- a/dom/html/HTMLFieldSetElement.h
+++ b/dom/html/HTMLFieldSetElement.h
@@ -42,9 +42,6 @@ public:
 
   virtual nsresult InsertChildBefore(nsIContent* aChild, nsIContent* aBeforeThis,
                                      bool aNotify) override;
-  virtual nsresult InsertChildAt_Deprecated(nsIContent* aChild, uint32_t aIndex,
-                                            bool aNotify) override;
-  virtual void RemoveChildAt_Deprecated(uint32_t aIndex, bool aNotify) override;
   virtual void RemoveChildNode(nsIContent* aKid, bool aNotify) override;
 
   // nsIFormControl
diff --git a/dom/html/HTMLOptGroupElement.cpp b/dom/html/HTMLOptGroupElement.cpp
index c3002dea9314..6792647195c9 100644
--- a/dom/html/HTMLOptGroupElement.cpp
+++ b/dom/html/HTMLOptGroupElement.cpp
@@ -86,28 +86,6 @@ HTMLOptGroupElement::InsertChildBefore(nsIContent* aKid,
   return rv;
 }
 
-nsresult
-HTMLOptGroupElement::InsertChildAt_Deprecated(nsIContent* aKid,
-                                              uint32_t aIndex,
-                                              bool aNotify)
-{
-  SafeOptionListMutation safeMutation(GetSelect(), this, aKid, aIndex, aNotify);
-  nsresult rv = nsGenericHTMLElement::InsertChildAt_Deprecated(aKid, aIndex,
-                                                               aNotify);
-  if (NS_FAILED(rv)) {
-    safeMutation.MutationFailed();
-  }
-  return rv;
-}
-
-void
-HTMLOptGroupElement::RemoveChildAt_Deprecated(uint32_t aIndex, bool aNotify)
-{
-  SafeOptionListMutation safeMutation(GetSelect(), this, nullptr, aIndex,
-                                      aNotify);
-  nsGenericHTMLElement::RemoveChildAt_Deprecated(aIndex, aNotify);
-}
-
 void
 HTMLOptGroupElement::RemoveChildNode(nsIContent* aKid, bool aNotify)
 {
diff --git a/dom/html/HTMLOptGroupElement.h b/dom/html/HTMLOptGroupElement.h
index 0784eb95fa5c..4c239853fe90 100644
--- a/dom/html/HTMLOptGroupElement.h
+++ b/dom/html/HTMLOptGroupElement.h
@@ -28,9 +28,6 @@ public:
   // nsINode
   virtual nsresult InsertChildBefore(nsIContent* aKid, nsIContent* aBeforeThis,
                                      bool aNotify) override;
-  virtual nsresult InsertChildAt_Deprecated(nsIContent* aKid, uint32_t aIndex,
-                                            bool aNotify) override;
-  virtual void RemoveChildAt_Deprecated(uint32_t aIndex, bool aNotify) override;
   virtual void RemoveChildNode(nsIContent* aKid, bool aNotify) override;
 
   // nsIContent
diff --git a/dom/html/HTMLPictureElement.cpp b/dom/html/HTMLPictureElement.cpp
index 98d846e78893..7f172aa27b8f 100644
--- a/dom/html/HTMLPictureElement.cpp
+++ b/dom/html/HTMLPictureElement.cpp
@@ -30,32 +30,6 @@ HTMLPictureElement::~HTMLPictureElement()
 
 NS_IMPL_ELEMENT_CLONE(HTMLPictureElement)
 
-void
-HTMLPictureElement::RemoveChildAt_Deprecated(uint32_t aIndex, bool aNotify)
-{
-  nsCOMPtr<nsIContent> child = GetChildAt_Deprecated(aIndex);
-
-  if (child && child->IsHTMLElement(nsGkAtoms::img)) {
-    HTMLImageElement* img = HTMLImageElement::FromNode(child);
-    if (img) {
-      img->PictureSourceRemoved(child->AsContent());
-    }
-  } else if (child && child->IsHTMLElement(nsGkAtoms::source)) {
-    // Find all img siblings after this <source> to notify them of its demise
-    nsCOMPtr<nsIContent> nextSibling = child->GetNextSibling();
-    if (nextSibling && nextSibling->GetParentNode() == this) {
-      do {
-        HTMLImageElement* img = HTMLImageElement::FromNode(nextSibling);
-        if (img) {
-          img->PictureSourceRemoved(child->AsContent());
-        }
-      } while ( (nextSibling = nextSibling->GetNextSibling()) );
-    }
-  }
-
-  nsGenericHTMLElement::RemoveChildAt_Deprecated(aIndex, aNotify);
-}
-
 void
 HTMLPictureElement::RemoveChildNode(nsIContent* aKid, bool aNotify)
 {
@@ -111,35 +85,6 @@ HTMLPictureElement::InsertChildBefore(nsIContent* aKid, nsIContent* aBeforeThis,
   return rv;
 }
 
-nsresult
-HTMLPictureElement::InsertChildAt_Deprecated(nsIContent* aKid, uint32_t aIndex, bool aNotify)
-{
-  nsresult rv = nsGenericHTMLElement::InsertChildAt_Deprecated(aKid, aIndex, aNotify);
-
-  NS_ENSURE_SUCCESS(rv, rv);
-  NS_ENSURE_TRUE(aKid, rv);
-
-  if (aKid->IsHTMLElement(nsGkAtoms::img)) {
-    HTMLImageElement* img = HTMLImageElement::FromNode(aKid);
-    if (img) {
-      img->PictureSourceAdded(aKid->AsContent());
-    }
-  } else if (aKid->IsHTMLElement(nsGkAtoms::source)) {
-    // Find all img siblings after this <source> to notify them of its insertion
-    nsCOMPtr<nsIContent> nextSibling = aKid->GetNextSibling();
-    if (nextSibling && nextSibling->GetParentNode() == this) {
-      do {
-        HTMLImageElement* img = HTMLImageElement::FromNode(nextSibling);
-        if (img) {
-          img->PictureSourceAdded(aKid->AsContent());
-        }
-      } while ( (nextSibling = nextSibling->GetNextSibling()) );
-    }
-  }
-
-  return rv;
-}
-
 JSObject*
 HTMLPictureElement::WrapNode(JSContext* aCx, JS::Handle<JSObject*> aGivenProto)
 {
diff --git a/dom/html/HTMLPictureElement.h b/dom/html/HTMLPictureElement.h
index 2b6ec48702dc..56c9321dd9d0 100644
--- a/dom/html/HTMLPictureElement.h
+++ b/dom/html/HTMLPictureElement.h
@@ -23,12 +23,9 @@ public:
 
   virtual nsresult Clone(mozilla::dom::NodeInfo* aNodeInfo, nsINode** aResult,
                          bool aPreallocateChildren) const override;
-  virtual void RemoveChildAt_Deprecated(uint32_t aIndex, bool aNotify) override;
   virtual void RemoveChildNode(nsIContent* aKid, bool aNotify) override;
   virtual nsresult InsertChildBefore(nsIContent* aKid, nsIContent* aBeforeThis,
                                      bool aNotify) override;
-  virtual nsresult InsertChildAt_Deprecated(nsIContent* aKid, uint32_t aIndex,
-                                            bool aNotify) override;
 
 protected:
   virtual ~HTMLPictureElement();
diff --git a/dom/html/HTMLSelectElement.cpp b/dom/html/HTMLSelectElement.cpp
index 8a7cee162f9f..7a7bf0a9bcda 100644
--- a/dom/html/HTMLSelectElement.cpp
+++ b/dom/html/HTMLSelectElement.cpp
@@ -217,28 +217,6 @@ HTMLSelectElement::InsertChildBefore(nsIContent* aKid,
   return rv;
 }
 
-nsresult
-HTMLSelectElement::InsertChildAt_Deprecated(nsIContent* aKid,
-                                            uint32_t aIndex,
-                                            bool aNotify)
-{
-  SafeOptionListMutation safeMutation(this, this, aKid, aIndex, aNotify);
-  nsresult rv =
-    nsGenericHTMLFormElementWithState::InsertChildAt_Deprecated(aKid, aIndex,
-                                                                aNotify);
-  if (NS_FAILED(rv)) {
-    safeMutation.MutationFailed();
-  }
-  return rv;
-}
-
-void
-HTMLSelectElement::RemoveChildAt_Deprecated(uint32_t aIndex, bool aNotify)
-{
-  SafeOptionListMutation safeMutation(this, this, nullptr, aIndex, aNotify);
-  nsGenericHTMLFormElementWithState::RemoveChildAt_Deprecated(aIndex, aNotify);
-}
-
 void
 HTMLSelectElement::RemoveChildNode(nsIContent* aKid, bool aNotify)
 {
diff --git a/dom/html/HTMLSelectElement.h b/dom/html/HTMLSelectElement.h
index 8945ddbdf404..27f448ff83ab 100644
--- a/dom/html/HTMLSelectElement.h
+++ b/dom/html/HTMLSelectElement.h
@@ -247,9 +247,6 @@ public:
   virtual bool IsHTMLFocusable(bool aWithMouse, bool* aIsFocusable, int32_t* aTabIndex) override;
   virtual nsresult InsertChildBefore(nsIContent* aKid, nsIContent* aBeforeThis,
                                      bool aNotify) override;
-  virtual nsresult InsertChildAt_Deprecated(nsIContent* aKid, uint32_t aIndex,
-                                            bool aNotify) override;
-  virtual void RemoveChildAt_Deprecated(uint32_t aIndex, bool aNotify) override;
   virtual void RemoveChildNode(nsIContent* aKid, bool aNotify) override;
 
   // Overriden nsIFormControl methods
diff --git a/dom/svg/SVGDocument.cpp b/dom/svg/SVGDocument.cpp
index cd65c062b2ab..16b1ad48b271 100644
--- a/dom/svg/SVGDocument.cpp
+++ b/dom/svg/SVGDocument.cpp
@@ -50,23 +50,6 @@ SVGDocument::InsertChildBefore(nsIContent* aKid, nsIContent* aBeforeThis,
   return XMLDocument::InsertChildBefore(aKid, aBeforeThis, aNotify);
 }
 
-nsresult
-SVGDocument::InsertChildAt_Deprecated(nsIContent* aKid, uint32_t aIndex,
-                                      bool aNotify)
-{
-  if (aKid->IsElement() && !aKid->IsSVGElement()) {
-    // We can get here when well formed XML with a non-SVG root element is
-    // served with the SVG MIME type, for example. In that case we need to load
-    // the non-SVG UA sheets or else we can get bugs like bug 1016145.  Note
-    // that we have to do this _before_ the
-    // XMLDocument::InsertChildAt_Deprecated call, since that can try to
-    // construct frames, and we need to have the sheets loaded by then.
-    EnsureNonSVGUserAgentStyleSheetsLoaded();
-  }
-
-  return XMLDocument::InsertChildAt_Deprecated(aKid, aIndex, aNotify);
-}
-
 nsresult
 SVGDocument::Clone(mozilla::dom::NodeInfo *aNodeInfo, nsINode **aResult,
                    bool aPreallocateChildren) const
diff --git a/dom/svg/SVGDocument.h b/dom/svg/SVGDocument.h
index 4e8907799b6d..f91e27908b98 100644
--- a/dom/svg/SVGDocument.h
+++ b/dom/svg/SVGDocument.h
@@ -35,8 +35,6 @@ public:
 
   virtual nsresult InsertChildBefore(nsIContent* aKid, nsIContent* aBeforeThis,
                                      bool aNotify) override;
-  virtual nsresult InsertChildAt_Deprecated(nsIContent* aKid, uint32_t aIndex,
-                                            bool aNotify) override;
   virtual nsresult Clone(mozilla::dom::NodeInfo *aNodeInfo, nsINode **aResult,
                          bool aPreallocateChildren) const override;
 
diff --git a/dom/svg/SVGSwitchElement.cpp b/dom/svg/SVGSwitchElement.cpp
index 6b5491dcc897..258964467393 100644
--- a/dom/svg/SVGSwitchElement.cpp
+++ b/dom/svg/SVGSwitchElement.cpp
@@ -93,26 +93,6 @@ SVGSwitchElement::InsertChildBefore(nsIContent* aKid, nsIContent* aBeforeThis,
   return rv;
 }
 
-nsresult
-SVGSwitchElement::InsertChildAt_Deprecated(nsIContent* aKid,
-                                           uint32_t aIndex,
-                                           bool aNotify)
-{
-  nsresult rv = SVGSwitchElementBase::InsertChildAt_Deprecated(aKid, aIndex,
-                                                               aNotify);
-  if (NS_SUCCEEDED(rv)) {
-    MaybeInvalidate();
-  }
-  return rv;
-}
-
-void
-SVGSwitchElement::RemoveChildAt_Deprecated(uint32_t aIndex, bool aNotify)
-{
-  SVGSwitchElementBase::RemoveChildAt_Deprecated(aIndex, aNotify);
-  MaybeInvalidate();
-}
-
 void
 SVGSwitchElement::RemoveChildNode(nsIContent* aKid, bool aNotify)
 {
diff --git a/dom/svg/SVGSwitchElement.h b/dom/svg/SVGSwitchElement.h
index 05d1e2db856f..2daa17fabf8f 100644
--- a/dom/svg/SVGSwitchElement.h
+++ b/dom/svg/SVGSwitchElement.h
@@ -42,9 +42,6 @@ public:
   // nsINode
   virtual nsresult InsertChildBefore(nsIContent* aKid, nsIContent* aBeforeThis,
                                      bool aNotify) override;
-  virtual nsresult InsertChildAt_Deprecated(nsIContent* aKid, uint32_t aIndex,
-                                            bool aNotify) override;
-  virtual void RemoveChildAt_Deprecated(uint32_t aIndex, bool aNotify) override;
   virtual void RemoveChildNode(nsIContent* aKid, bool aNotify) override;
 
   // nsIContent
diff --git a/dom/xul/nsXULElement.cpp b/dom/xul/nsXULElement.cpp
index 4fe260649fe8..0fb5efc0a840 100644
--- a/dom/xul/nsXULElement.cpp
+++ b/dom/xul/nsXULElement.cpp
@@ -827,103 +827,6 @@ nsXULElement::UnbindFromTree(bool aDeep, bool aNullParent)
     nsStyledElement::UnbindFromTree(aDeep, aNullParent);
 }
 
-void
-nsXULElement::RemoveChildAt_Deprecated(uint32_t aIndex, bool aNotify)
-{
-    nsCOMPtr<nsIContent> oldKid = mAttrsAndChildren.GetSafeChildAt(aIndex);
-    if (!oldKid) {
-      return;
-    }
-
-    // On the removal of a <treeitem>, <treechildren>, or <treecell> element,
-    // the possibility exists that some of the items in the removed subtree
-    // are selected (and therefore need to be deselected). We need to account for this.
-    nsCOMPtr<nsIDOMXULMultiSelectControlElement> controlElement;
-    nsCOMPtr<nsIListBoxObject> listBox;
-    bool fireSelectionHandler = false;
-
-    // -1 = do nothing, -2 = null out current item
-    // anything else = index to re-set as current
-    int32_t newCurrentIndex = -1;
-
-    if (oldKid->NodeInfo()->Equals(nsGkAtoms::listitem, kNameSpaceID_XUL)) {
-      // This is the nasty case. We have (potentially) a slew of selected items
-      // and cells going away.
-      // First, retrieve the tree.
-      // Check first whether this element IS the tree
-      controlElement = do_QueryObject(this);
-
-      // If it's not, look at our parent
-      if (!controlElement)
-        GetParentTree(getter_AddRefs(controlElement));
-      nsCOMPtr<nsIContent> controlContent(do_QueryInterface(controlElement));
-      RefPtr<nsXULElement> xulElement = FromNodeOrNull(controlContent);
-
-      if (xulElement) {
-        // Iterate over all of the items and find out if they are contained inside
-        // the removed subtree.
-        int32_t length;
-        controlElement->GetSelectedCount(&length);
-        for (int32_t i = 0; i < length; i++) {
-          nsCOMPtr<nsIDOMXULSelectControlItemElement> item;
-          controlElement->MultiGetSelectedItem(i, getter_AddRefs(item));
-          nsCOMPtr<nsINode> node = do_QueryInterface(item);
-          if (node == oldKid &&
-              NS_SUCCEEDED(controlElement->RemoveItemFromSelection(item))) {
-            length--;
-            i--;
-            fireSelectionHandler = true;
-          }
-        }
-
-        nsCOMPtr<nsIDOMXULSelectControlItemElement> curItem;
-        controlElement->GetCurrentItem(getter_AddRefs(curItem));
-        nsCOMPtr<nsIContent> curNode = do_QueryInterface(curItem);
-        if (curNode && nsContentUtils::ContentIsDescendantOf(curNode, oldKid)) {
-            // Current item going away
-            nsCOMPtr<nsIBoxObject> box = xulElement->GetBoxObject(IgnoreErrors());
-            listBox = do_QueryInterface(box);
-            if (listBox) {
-              listBox->GetIndexOfItem(oldKid->AsElement(), &newCurrentIndex);
-            }
-
-            // If any of this fails, we'll just set the current item to null
-            if (newCurrentIndex == -1)
-              newCurrentIndex = -2;
-        }
-      }
-    }
-
-    nsStyledElement::RemoveChildAt_Deprecated(aIndex, aNotify);
-
-    if (newCurrentIndex == -2) {
-        controlElement->SetCurrentItem(nullptr);
-    } else if (newCurrentIndex > -1) {
-        // Make sure the index is still valid
-        int32_t treeRows;
-        listBox->GetRowCount(&treeRows);
-        if (treeRows > 0) {
-            newCurrentIndex = std::min((treeRows - 1), newCurrentIndex);
-            RefPtr<Element> newCurrentItem;
-            listBox->GetItemAtIndex(newCurrentIndex, getter_AddRefs(newCurrentItem));
-            nsCOMPtr<nsIDOMXULSelectControlItemElement> xulCurItem = do_QueryInterface(newCurrentItem);
-            if (xulCurItem)
-                controlElement->SetCurrentItem(xulCurItem);
-        } else {
-            controlElement->SetCurrentItem(nullptr);
-        }
-    }
-
-    nsIDocument* doc;
-    if (fireSelectionHandler && (doc = GetComposedDoc())) {
-      nsContentUtils::DispatchTrustedEvent(doc,
-                                           static_cast<nsIContent*>(this),
-                                           NS_LITERAL_STRING("select"),
-                                           false,
-                                           true);
-    }
-}
-
 void
 nsXULElement::RemoveChildNode(nsIContent* aKid, bool aNotify)
 {
diff --git a/dom/xul/nsXULElement.h b/dom/xul/nsXULElement.h
index dbbc51f880b3..2019c9d9f55b 100644
--- a/dom/xul/nsXULElement.h
+++ b/dom/xul/nsXULElement.h
@@ -368,7 +368,6 @@ public:
                                 nsIContent* aBindingParent,
                                 bool aCompileEventHandlers) override;
     virtual void UnbindFromTree(bool aDeep, bool aNullParent) override;
-    virtual void RemoveChildAt_Deprecated(uint32_t aIndex, bool aNotify) override;
     virtual void RemoveChildNode(nsIContent* aKid, bool aNotify) override;
     virtual void DestroyContent() override;