--- a/editor/libeditor/EditorBase.cpp
+++ b/editor/libeditor/EditorBase.cpp
@@ -1382,36 +1382,42 @@ already_AddRefed<Element>
 EditorBase::CreateNode(nsIAtom* aTag,
                        nsINode* aParent,
                        int32_t aPosition)
 {
   MOZ_ASSERT(aTag && aParent);
 
   AutoRules beginRulesSniffing(this, EditAction::createNode, nsIEditor::eNext);
 
-  for (auto& listener : mActionListeners) {
-    listener->WillCreateNode(nsDependentAtomString(aTag),
-                             GetAsDOMNode(aParent), aPosition);
+  {
+    AutoActionListenerArray listeners(mActionListeners);
+    for (auto& listener : listeners) {
+      listener->WillCreateNode(nsDependentAtomString(aTag),
+                               GetAsDOMNode(aParent), aPosition);
+    }
   }
 
   nsCOMPtr<Element> ret;
 
   RefPtr<CreateElementTransaction> transaction =
     CreateTxnForCreateElement(*aTag, *aParent, aPosition);
   nsresult rv = DoTransaction(transaction);
   if (NS_SUCCEEDED(rv)) {
     ret = transaction->GetNewNode();
     MOZ_ASSERT(ret);
   }
 
   mRangeUpdater.SelAdjCreateNode(aParent, aPosition);
 
-  for (auto& listener : mActionListeners) {
-    listener->DidCreateNode(nsDependentAtomString(aTag), GetAsDOMNode(ret),
-                            GetAsDOMNode(aParent), aPosition, rv);
+  {
+    AutoActionListenerArray listeners(mActionListeners);
+    for (auto& listener : listeners) {
+      listener->DidCreateNode(nsDependentAtomString(aTag), GetAsDOMNode(ret),
+                              GetAsDOMNode(aParent), aPosition, rv);
+    }
   }
 
   return ret.forget();
 }
 
 NS_IMETHODIMP
 EditorBase::InsertNode(nsIDOMNode* aNode,
                        nsIDOMNode* aParent,
@@ -1426,30 +1432,36 @@ EditorBase::InsertNode(nsIDOMNode* aNode
 
 nsresult
 EditorBase::InsertNode(nsIContent& aNode,
                        nsINode& aParent,
                        int32_t aPosition)
 {
   AutoRules beginRulesSniffing(this, EditAction::insertNode, nsIEditor::eNext);
 
-  for (auto& listener : mActionListeners) {
-    listener->WillInsertNode(aNode.AsDOMNode(), aParent.AsDOMNode(),
-                             aPosition);
+  {
+    AutoActionListenerArray listeners(mActionListeners);
+    for (auto& listener : listeners) {
+      listener->WillInsertNode(aNode.AsDOMNode(), aParent.AsDOMNode(),
+                               aPosition);
+    }
   }
 
   RefPtr<InsertNodeTransaction> transaction =
     CreateTxnForInsertNode(aNode, aParent, aPosition);
   nsresult rv = DoTransaction(transaction);
 
   mRangeUpdater.SelAdjInsertNode(aParent.AsDOMNode(), aPosition);
 
-  for (auto& listener : mActionListeners) {
-    listener->DidInsertNode(aNode.AsDOMNode(), aParent.AsDOMNode(), aPosition,
-                            rv);
+  {
+    AutoActionListenerArray listeners(mActionListeners);
+    for (auto& listener : listeners) {
+      listener->DidInsertNode(aNode.AsDOMNode(), aParent.AsDOMNode(), aPosition,
+                              rv);
+    }
   }
 
   return rv;
 }
 
 NS_IMETHODIMP
 EditorBase::SplitNode(nsIDOMNode* aNode,
                       int32_t aOffset,
@@ -1465,33 +1477,39 @@ EditorBase::SplitNode(nsIDOMNode* aNode,
 
 nsIContent*
 EditorBase::SplitNode(nsIContent& aNode,
                       int32_t aOffset,
                       ErrorResult& aResult)
 {
   AutoRules beginRulesSniffing(this, EditAction::splitNode, nsIEditor::eNext);
 
-  for (auto& listener : mActionListeners) {
-    listener->WillSplitNode(aNode.AsDOMNode(), aOffset);
+  {
+    AutoActionListenerArray listeners(mActionListeners);
+    for (auto& listener : listeners) {
+      listener->WillSplitNode(aNode.AsDOMNode(), aOffset);
+    }
   }
 
   RefPtr<SplitNodeTransaction> transaction =
     CreateTxnForSplitNode(aNode, aOffset);
   aResult = DoTransaction(transaction);
 
   nsCOMPtr<nsIContent> newNode = aResult.Failed() ? nullptr
                                                   : transaction->GetNewNode();
 
   mRangeUpdater.SelAdjSplitNode(aNode, aOffset, newNode);
 
   nsresult rv = aResult.StealNSResult();
-  for (auto& listener : mActionListeners) {
-    listener->DidSplitNode(aNode.AsDOMNode(), aOffset, GetAsDOMNode(newNode),
-                           rv);
+  {
+    AutoActionListenerArray listeners(mActionListeners);
+    for (auto& listener : listeners) {
+      listener->DidSplitNode(aNode.AsDOMNode(), aOffset, GetAsDOMNode(newNode),
+                             rv);
+    }
   }
   // Note: result might be a success code, so we can't use Throw() to
   // set it on aResult.
   aResult = rv;
 
   return newNode;
 }
 
@@ -1517,34 +1535,40 @@ EditorBase::JoinNodes(nsINode& aLeftNode
                                nsIEditor::ePrevious);
 
   // Remember some values; later used for saved selection updating.
   // Find the offset between the nodes to be joined.
   int32_t offset = parent->IndexOf(&aRightNode);
   // Find the number of children of the lefthand node
   uint32_t oldLeftNodeLen = aLeftNode.Length();
 
-  for (auto& listener : mActionListeners) {
-    listener->WillJoinNodes(aLeftNode.AsDOMNode(), aRightNode.AsDOMNode(),
-                            parent->AsDOMNode());
+  {
+    AutoActionListenerArray listeners(mActionListeners);
+    for (auto& listener : listeners) {
+      listener->WillJoinNodes(aLeftNode.AsDOMNode(), aRightNode.AsDOMNode(),
+                              parent->AsDOMNode());
+    }
   }
 
   nsresult rv = NS_OK;
   RefPtr<JoinNodeTransaction> transaction =
     CreateTxnForJoinNode(aLeftNode, aRightNode);
   if (transaction)  {
     rv = DoTransaction(transaction);
   }
 
   mRangeUpdater.SelAdjJoinNodes(aLeftNode, aRightNode, *parent, offset,
                                 (int32_t)oldLeftNodeLen);
 
-  for (auto& listener : mActionListeners) {
-    listener->DidJoinNodes(aLeftNode.AsDOMNode(), aRightNode.AsDOMNode(),
-                           parent->AsDOMNode(), rv);
+  {
+    AutoActionListenerArray listeners(mActionListeners);
+    for (auto& listener : listeners) {
+      listener->DidJoinNodes(aLeftNode.AsDOMNode(), aRightNode.AsDOMNode(),
+                             parent->AsDOMNode(), rv);
+    }
   }
 
   return rv;
 }
 
 NS_IMETHODIMP
 EditorBase::DeleteNode(nsIDOMNode* aNode)
 {
@@ -1555,28 +1579,34 @@ EditorBase::DeleteNode(nsIDOMNode* aNode
 
 nsresult
 EditorBase::DeleteNode(nsINode* aNode)
 {
   AutoRules beginRulesSniffing(this, EditAction::createNode,
                                nsIEditor::ePrevious);
 
   // save node location for selection updating code.
-  for (auto& listener : mActionListeners) {
-    listener->WillDeleteNode(aNode->AsDOMNode());
+  {
+    AutoActionListenerArray listeners(mActionListeners);
+    for (auto& listener : listeners) {
+      listener->WillDeleteNode(aNode->AsDOMNode());
+    }
   }
 
   RefPtr<DeleteNodeTransaction> transaction;
   nsresult rv = CreateTxnForDeleteNode(aNode, getter_AddRefs(transaction));
   if (NS_SUCCEEDED(rv))  {
     rv = DoTransaction(transaction);
   }
 
-  for (auto& listener : mActionListeners) {
-    listener->DidDeleteNode(aNode->AsDOMNode(), rv);
+  {
+    AutoActionListenerArray listeners(mActionListeners);
+    for (auto& listener : listeners) {
+      listener->DidDeleteNode(aNode->AsDOMNode(), rv);
+    }
   }
 
   NS_ENSURE_SUCCESS(rv, rv);
   return NS_OK;
 }
 
 /**
  * ReplaceContainer() replaces inNode with a new node (outNode) which is
@@ -2503,33 +2533,39 @@ EditorBase::InsertTextIntoTextNodeImpl(c
     insertedTextNode = mIMETextNode;
     insertedOffset = mIMETextOffset;
     mIMETextLength = aStringToInsert.Length();
   } else {
     transaction = CreateTxnForInsertText(aStringToInsert, aTextNode, aOffset);
   }
 
   // Let listeners know what's up
-  for (auto& listener : mActionListeners) {
-    listener->WillInsertText(
-      static_cast<nsIDOMCharacterData*>(insertedTextNode->AsDOMNode()),
-      insertedOffset, aStringToInsert);
+  {
+    AutoActionListenerArray listeners(mActionListeners);
+    for (auto& listener : listeners) {
+      listener->WillInsertText(
+        static_cast<nsIDOMCharacterData*>(insertedTextNode->AsDOMNode()),
+        insertedOffset, aStringToInsert);
+    }
   }
 
   // XXX We may not need these view batches anymore.  This is handled at a
   // higher level now I believe.
   BeginUpdateViewBatch();
   nsresult rv = DoTransaction(transaction);
   EndUpdateViewBatch();
 
   // let listeners know what happened
-  for (auto& listener : mActionListeners) {
-    listener->DidInsertText(
-      static_cast<nsIDOMCharacterData*>(insertedTextNode->AsDOMNode()),
-      insertedOffset, aStringToInsert, rv);
+  {
+    AutoActionListenerArray listeners(mActionListeners);
+    for (auto& listener : listeners) {
+      listener->DidInsertText(
+        static_cast<nsIDOMCharacterData*>(insertedTextNode->AsDOMNode()),
+        insertedOffset, aStringToInsert, rv);
+    }
   }
 
   // Added some cruft here for bug 43366.  Layout was crashing because we left
   // an empty text node lying around in the document.  So I delete empty text
   // nodes caused by IME.  I have to mark the IME transaction as "fixed", which
   // means that furure IME txns won't merge with it.  This is because we don't
   // want future IME txns trying to put their text into a node that is no
   // longer in the document.  This does not break undo/redo, because all these
@@ -2654,29 +2690,35 @@ EditorBase::DeleteText(nsGenericDOMDataN
   RefPtr<DeleteTextTransaction> transaction =
     CreateTxnForDeleteText(aCharData, aOffset, aLength);
   NS_ENSURE_STATE(transaction);
 
   AutoRules beginRulesSniffing(this, EditAction::deleteText,
                                nsIEditor::ePrevious);
 
   // Let listeners know what's up
-  for (auto& listener : mActionListeners) {
-    listener->WillDeleteText(
-        static_cast<nsIDOMCharacterData*>(GetAsDOMNode(&aCharData)), aOffset,
-        aLength);
+  {
+    AutoActionListenerArray listeners(mActionListeners);
+    for (auto& listener : listeners) {
+      listener->WillDeleteText(
+          static_cast<nsIDOMCharacterData*>(GetAsDOMNode(&aCharData)), aOffset,
+          aLength);
+    }
   }
 
   nsresult rv = DoTransaction(transaction);
 
   // Let listeners know what happened
-  for (auto& listener : mActionListeners) {
-    listener->DidDeleteText(
-        static_cast<nsIDOMCharacterData*>(GetAsDOMNode(&aCharData)), aOffset,
-        aLength, rv);
+  {
+    AutoActionListenerArray listeners(mActionListeners);
+    for (auto& listener : listeners) {
+      listener->DidDeleteText(
+          static_cast<nsIDOMCharacterData*>(GetAsDOMNode(&aCharData)), aOffset,
+          aLength, rv);
+    }
   }
 
   return rv;
 }
 
 already_AddRefed<DeleteTextTransaction>
 EditorBase::CreateTxnForDeleteText(nsGenericDOMDataNode& aCharData,
                                    uint32_t aOffset,
@@ -4030,45 +4072,51 @@ EditorBase::DeleteSelectionImpl(EDirecti
                                             getter_AddRefs(deleteNode),
                                             &deleteCharOffset,
                                             &deleteCharLength);
   nsCOMPtr<nsIDOMCharacterData> deleteCharData(do_QueryInterface(deleteNode));
 
   if (NS_SUCCEEDED(rv)) {
     AutoRules beginRulesSniffing(this, EditAction::deleteSelection, aAction);
     // Notify nsIEditActionListener::WillDelete[Selection|Text|Node]
-    if (!deleteNode) {
-      for (auto& listener : mActionListeners) {
-        listener->WillDeleteSelection(selection);
-      }
-    } else if (deleteCharData) {
-      for (auto& listener : mActionListeners) {
-        listener->WillDeleteText(deleteCharData, deleteCharOffset, 1);
-      }
-    } else {
-      for (auto& listener : mActionListeners) {
-        listener->WillDeleteNode(deleteNode->AsDOMNode());
+    {
+      AutoActionListenerArray listeners(mActionListeners);
+      if (!deleteNode) {
+        for (auto& listener : listeners) {
+          listener->WillDeleteSelection(selection);
+        }
+      } else if (deleteCharData) {
+        for (auto& listener : listeners) {
+          listener->WillDeleteText(deleteCharData, deleteCharOffset, 1);
+        }
+      } else {
+        for (auto& listener : listeners) {
+          listener->WillDeleteNode(deleteNode->AsDOMNode());
+        }
       }
     }
 
     // Delete the specified amount
     rv = DoTransaction(transaction);
 
     // Notify nsIEditActionListener::DidDelete[Selection|Text|Node]
-    if (!deleteNode) {
-      for (auto& listener : mActionListeners) {
-        listener->DidDeleteSelection(selection);
-      }
-    } else if (deleteCharData) {
-      for (auto& listener : mActionListeners) {
-        listener->DidDeleteText(deleteCharData, deleteCharOffset, 1, rv);
-      }
-    } else {
-      for (auto& listener : mActionListeners) {
-        listener->DidDeleteNode(deleteNode->AsDOMNode(), rv);
+    {
+      AutoActionListenerArray listeners(mActionListeners);
+      if (!deleteNode) {
+        for (auto& listener : mActionListeners) {
+          listener->DidDeleteSelection(selection);
+        }
+      } else if (deleteCharData) {
+        for (auto& listener : mActionListeners) {
+          listener->DidDeleteText(deleteCharData, deleteCharOffset, 1, rv);
+        }
+      } else {
+        for (auto& listener : mActionListeners) {
+          listener->DidDeleteNode(deleteNode->AsDOMNode(), rv);
+        }
       }
     }
   }
 
   return rv;
 }
 
 already_AddRefed<Element>

--- a/editor/libeditor/EditorBase.h
+++ b/editor/libeditor/EditorBase.h
@@ -20,16 +20,17 @@
 #include "nsIObserver.h"                // for NS_DECL_NSIOBSERVER, etc.
 #include "nsIPhonetic.h"                // for NS_DECL_NSIPHONETIC, etc.
 #include "nsIPlaintextEditor.h"         // for nsIPlaintextEditor, etc.
 #include "nsISelectionController.h"     // for nsISelectionController constants
 #include "nsISupportsImpl.h"            // for EditorBase::Release, etc.
 #include "nsIWeakReferenceUtils.h"      // for nsWeakPtr
 #include "nsLiteralString.h"            // for NS_LITERAL_STRING
 #include "nsString.h"                   // for nsCString
+#include "nsTArray.h"                   // for nsTArray and nsAutoTArray
 #include "nsWeakReference.h"            // for nsSupportsWeakReference
 #include "nscore.h"                     // for nsresult, nsAString, etc.
 
 class nsIAtom;
 class nsIContent;
 class nsIDOMDocument;
 class nsIDOMEvent;
 class nsIDOMEventListener;
@@ -997,17 +998,19 @@ protected:
   // Saved selection state for placeholder transaction batching.
   SelectionState* mSelState;
   nsString* mPhonetic;
   // IME composition this is not null between compositionstart and
   // compositionend.
   RefPtr<TextComposition> mComposition;
 
   // Listens to all low level actions on the doc.
-  nsTArray<OwningNonNull<nsIEditActionListener>> mActionListeners;
+  typedef AutoTArray<OwningNonNull<nsIEditActionListener>, 5>
+            AutoActionListenerArray;
+  AutoActionListenerArray mActionListeners;
   // Just notify once per high level change.
   nsTArray<OwningNonNull<nsIEditorObserver>> mEditorObservers;
   // Listen to overall doc state (dirty or not, just created, etc.).
   nsTArray<OwningNonNull<nsIDocumentStateListener>> mDocStateListeners;
 
   // Cached selection for AutoSelectionRestorer.
   SelectionState mSavedSel;
   // Utility class object for maintaining preserved ranges.