diff --git a/editor/libeditor/HTMLEditRules.cpp b/editor/libeditor/HTMLEditRules.cpp
index 0045d856703e..72fa8a4f26c5 100644
--- a/editor/libeditor/HTMLEditRules.cpp
+++ b/editor/libeditor/HTMLEditRules.cpp
@@ -754,12 +754,6 @@ nsresult HTMLEditRules::WillDoAction(EditSubActionInfo& aInfo, bool* aCancel,
   *aCancel = false;
   *aHandled = false;
 
-  // Deal with actions for which we don't need to check whether the selection is
-  // editable.
-  if (aInfo.mEditSubAction == EditSubAction::eComputeTextToOutput) {
-    return TextEditRules::WillDoAction(aInfo, aCancel, aHandled);
-  }
-
   AutoSafeEditorData setData(*this, *mHTMLEditor);
 
   EditActionResult result = HTMLEditorRef().CanHandleHTMLEditSubAction();
@@ -786,6 +780,7 @@ nsresult HTMLEditRules::WillDoAction(EditSubActionInfo& aInfo, bool* aCancel,
       NS_WARNING_ASSERTION(NS_SUCCEEDED(rv), "WillInsert() failed");
       return NS_OK;
     }
+    case EditSubAction::eComputeTextToOutput:
     case EditSubAction::eCreateOrChangeDefinitionListItem:
     case EditSubAction::eCreateOrChangeList:
     case EditSubAction::eCreateOrRemoveBlock:
@@ -825,6 +820,7 @@ nsresult HTMLEditRules::DidDoAction(EditSubActionInfo& aInfo,
     case EditSubAction::eInsertElement:
     case EditSubAction::eInsertQuotedText:
       return NS_OK;
+    case EditSubAction::eComputeTextToOutput:
     case EditSubAction::eCreateOrChangeDefinitionListItem:
     case EditSubAction::eCreateOrChangeList:
     case EditSubAction::eCreateOrRemoveBlock:
diff --git a/editor/libeditor/TextEditRules.cpp b/editor/libeditor/TextEditRules.cpp
index 6bbae2fa4d19..913a8eab6bd5 100644
--- a/editor/libeditor/TextEditRules.cpp
+++ b/editor/libeditor/TextEditRules.cpp
@@ -205,9 +205,6 @@ nsresult TextEditRules::WillDoAction(EditSubActionInfo& aInfo, bool* aCancel,
     case EditSubAction::eSetText:
       TextEditorRef().UndefineCaretBidiLevel();
       return WillSetText(aCancel, aHandled, aInfo.inString, aInfo.maxLength);
-    case EditSubAction::eComputeTextToOutput:
-      return WillOutputText(aInfo.outputFormat, aInfo.outString, aInfo.flags,
-                            aCancel, aHandled);
     case EditSubAction::eInsertQuotedText: {
       CANCEL_OPERATION_IF_READONLY_OR_DISABLED
 
@@ -221,6 +218,7 @@ nsresult TextEditRules::WillDoAction(EditSubActionInfo& aInfo, bool* aCancel,
                            "Failed to remove padding <br> element");
       return rv;
     }
+    case EditSubAction::eComputeTextToOutput:
     case EditSubAction::eDeleteSelectedContent:
     case EditSubAction::eInsertElement:
     case EditSubAction::eInsertLineBreak:
@@ -242,6 +240,7 @@ nsresult TextEditRules::DidDoAction(EditSubActionInfo& aInfo,
   }
 
   switch (aInfo.mEditSubAction) {
+    case EditSubAction::eComputeTextToOutput:
     case EditSubAction::eDeleteSelectedContent:
     case EditSubAction::eInsertElement:
     case EditSubAction::eInsertLineBreak:
@@ -900,61 +899,35 @@ EditActionResult TextEditor::HandleDeleteSelectionInternal(
   return EditActionHandled(rv);
 }
 
-nsresult TextEditRules::WillOutputText(const nsAString* aOutputFormat,
-                                       nsAString* aOutString, uint32_t aFlags,
-                                       bool* aCancel, bool* aHandled) {
-  MOZ_ASSERT(IsEditorDataAvailable());
-
-  // null selection ok
-  if (NS_WARN_IF(!aOutString) || NS_WARN_IF(!aOutputFormat) ||
-      NS_WARN_IF(!aCancel) || NS_WARN_IF(!aHandled)) {
-    return NS_ERROR_NULL_POINTER;
-  }
-
-  // initialize out param
-  *aCancel = false;
-  *aHandled = false;
-
-  if (!aOutputFormat->LowerCaseEqualsLiteral("text/plain")) {
-    return NS_OK;
-  }
+EditActionResult TextEditor::ComputeValueFromTextNodeAndPaddingBRElement(
+    nsAString& aValue) const {
+  MOZ_ASSERT(IsEditActionDataAvailable());
 
   // If there is a padding <br> element, there's no content.  So output empty
   // string.
-  if (TextEditorRef().HasPaddingBRElementForEmptyEditor()) {
-    aOutString->Truncate();
-    *aHandled = true;
-    return NS_OK;
-  }
-
-  // If it's necessary to check selection range or the editor wraps hard,
-  // we need some complicated handling.  In such case, we need to use the
-  // expensive path.
-  // XXX Anything else what we cannot return plain text simply?
-  if (aFlags & nsIDocumentEncoder::OutputSelectionOnly ||
-      aFlags & nsIDocumentEncoder::OutputWrap) {
-    return NS_OK;
+  if (HasPaddingBRElementForEmptyEditor()) {
+    aValue.Truncate();
+    return EditActionHandled();
   }
 
   // If it's neither <input type="text"> nor <textarea>, e.g., an HTML editor
   // which is in plaintext mode (e.g., plaintext email composer on Thunderbird),
   // it should be handled by the expensive path.
-  if (TextEditorRef().AsHTMLEditor()) {
-    return NS_OK;
+  if (AsHTMLEditor()) {
+    return EditActionIgnored();
   }
 
-  Element* root = TextEditorRef().GetRoot();
-  if (!root) {  // Don't warn it, this is possible, e.g., 997805.html
-    aOutString->Truncate();
-    *aHandled = true;
-    return NS_OK;
+  Element* anonymousDivElement = GetRoot();
+  if (!anonymousDivElement) {
+    // Don't warn this case, this is possible, e.g., 997805.html
+    aValue.Truncate();
+    return EditActionHandled();
   }
 
-  nsIContent* firstChild = root->GetFirstChild();
-  if (!firstChild) {
-    aOutString->Truncate();
-    *aHandled = true;
-    return NS_OK;
+  nsIContent* textNodeOrPaddingBRElement = anonymousDivElement->GetFirstChild();
+  if (!textNodeOrPaddingBRElement) {
+    aValue.Truncate();
+    return EditActionHandled();
   }
 
   // If it's an <input type="text"> element, the DOM tree should be:
@@ -970,9 +943,17 @@ nsresult TextEditRules::WillOutputText(const nsAString* aOutputFormat,
   //   ...
   // </div>
 
-  Text* text = firstChild->GetAsText();
+  Text* textNode = textNodeOrPaddingBRElement->GetAsText();
+  if (!textNode) {
+    // If there is no text node in the expected DOM tree, we can say that it's
+    // just empty.
+    aValue.Truncate();
+    return EditActionHandled();
+  }
+
   nsIContent* firstChildExceptText =
-      text ? firstChild->GetNextSibling() : firstChild;
+      textNode ? textNodeOrPaddingBRElement->GetNextSibling()
+               : textNodeOrPaddingBRElement;
   // If the DOM tree is unexpected, fall back to the expensive path.
   bool isInput = IsSingleLineEditor();
   bool isTextarea = !isInput;
@@ -982,22 +963,12 @@ nsresult TextEditRules::WillOutputText(const nsAString* aOutputFormat,
                  !EditorBase::IsPaddingBRElementForEmptyLastLine(
                      *firstChildExceptText) &&
                  !firstChildExceptText->IsXULElement(nsGkAtoms::scrollbar))) {
-    return NS_OK;
+    return EditActionIgnored();
   }
 
-  // If there is no text node in the expected DOM tree, we can say that it's
-  // just empty.
-  if (!text) {
-    aOutString->Truncate();
-    *aHandled = true;
-    return NS_OK;
-  }
-
-  // Otherwise, the text is the value.
-  text->GetData(*aOutString);
-
-  *aHandled = true;
-  return NS_OK;
+  // Otherwise, the text data is the value.
+  textNode->GetData(aValue);
+  return EditActionHandled();
 }
 
 nsresult TextEditRules::CreateTrailingBRIfNeeded() {
diff --git a/editor/libeditor/TextEditRules.h b/editor/libeditor/TextEditRules.h
index 7ac0c3ed8d0f..94812d91dd76 100644
--- a/editor/libeditor/TextEditRules.h
+++ b/editor/libeditor/TextEditRules.h
@@ -122,17 +122,6 @@ class TextEditRules {
                                     const nsAString* inString,
                                     int32_t aMaxLength);
 
-  /**
-   * Called prior to nsIEditor::OutputToString.
-   *
-   * @param aInFormat  The format requested for the output, a MIME type.
-   * @param aOutText   The string to use for output, if aCancel is set to true.
-   * @param aOutCancel If set to true, the caller should cancel the operation
-   *                   and use aOutText as the result.
-   */
-  nsresult WillOutputText(const nsAString* aInFormat, nsAString* aOutText,
-                          uint32_t aFlags, bool* aOutCancel, bool* aHandled);
-
   /**
    * Creates a trailing break in the text doc if there is not one already.
    */
diff --git a/editor/libeditor/TextEditor.cpp b/editor/libeditor/TextEditor.cpp
index 260f91077fc1..aa681de32794 100644
--- a/editor/libeditor/TextEditor.cpp
+++ b/editor/libeditor/TextEditor.cpp
@@ -1851,12 +1851,10 @@ TextEditor::OutputToString(const nsAString& aFormatType,
 
   nsresult rv =
       ComputeValueInternal(aFormatType, aDocumentEncoderFlags, aOutputString);
-  if (NS_WARN_IF(NS_FAILED(rv))) {
-    // This is low level API for XUL applcation.  So, we should return raw
-    // error code here.
-    return rv;
-  }
-  return NS_OK;
+  NS_WARNING_ASSERTION(NS_SUCCEEDED(rv), "ComputeValueInternal() failed");
+  // This is low level API for XUL application.  So, we should return raw
+  // error code here.
+  return rv;
 }
 
 nsresult TextEditor::ComputeValueInternal(const nsAString& aFormatType,
@@ -1864,27 +1862,26 @@ nsresult TextEditor::ComputeValueInternal(const nsAString& aFormatType,
                                           nsAString& aOutputString) const {
   MOZ_ASSERT(IsEditActionDataAvailable());
 
-  // Protect the edit rules object from dying
-  RefPtr<TextEditRules> rules(mRules);
-
-  EditSubActionInfo subActionInfo(EditSubAction::eComputeTextToOutput);
-  subActionInfo.outString = &aOutputString;
-  subActionInfo.flags = aDocumentEncoderFlags;
-  subActionInfo.outputFormat = &aFormatType;
-
-  bool cancel{false};
-  bool handled{false};
-  nsresult rv = rules->WillDoAction(subActionInfo, &cancel, &handled);
-  if (NS_FAILED(rv) || cancel) {
-    return rv;
-  }
-  if (handled) {
-    // This case will get triggered by password fields or single text node only.
-    return rv;
+  // First, let's try to get the value simply only from text node if the
+  // caller wants plaintext value.
+  if (aFormatType.LowerCaseEqualsLiteral("text/plain")) {
+    // If it's necessary to check selection range or the editor wraps hard,
+    // we need some complicated handling.  In such case, we need to use the
+    // expensive path.
+    // XXX Anything else what we cannot return the text node data simply?
+    if (!(aDocumentEncoderFlags & (nsIDocumentEncoder::OutputSelectionOnly |
+                                   nsIDocumentEncoder::OutputWrap))) {
+      EditActionResult result =
+          ComputeValueFromTextNodeAndPaddingBRElement(aOutputString);
+      if (NS_WARN_IF(result.Failed()) || result.Canceled() ||
+          result.Handled()) {
+        return result.Rv();
+      }
+    }
   }
 
   nsAutoCString charset;
-  rv = GetDocumentCharsetInternal(charset);
+  nsresult rv = GetDocumentCharsetInternal(charset);
   if (NS_FAILED(rv) || charset.IsEmpty()) {
     charset.AssignLiteral("windows-1252");
   }
@@ -1895,12 +1892,10 @@ nsresult TextEditor::ComputeValueInternal(const nsAString& aFormatType,
     return NS_ERROR_FAILURE;
   }
 
-  // XXX Why don't we call TextEditRules::DidDoAction() here?
   rv = encoder->EncodeToString(aOutputString);
-  if (NS_WARN_IF(NS_FAILED(rv))) {
-    return rv;
-  }
-  return NS_OK;
+  NS_WARNING_ASSERTION(NS_SUCCEEDED(rv),
+                       "nsIDocumentEncoder::EncodeToString() failed");
+  return rv;
 }
 
 nsresult TextEditor::PasteAsQuotationAsAction(int32_t aClipboardType,
@@ -2010,7 +2005,7 @@ nsresult TextEditor::InsertWithQuotationsAsSubAction(
 }
 
 nsresult TextEditor::SharedOutputString(uint32_t aFlags, bool* aIsCollapsed,
-                                        nsAString& aResult) {
+                                        nsAString& aResult) const {
   MOZ_ASSERT(IsEditActionDataAvailable());
 
   *aIsCollapsed = SelectionRefPtr()->IsCollapsed();
@@ -2019,7 +2014,10 @@ nsresult TextEditor::SharedOutputString(uint32_t aFlags, bool* aIsCollapsed,
     aFlags |= nsIDocumentEncoder::OutputSelectionOnly;
   }
   // If the selection isn't collapsed, we'll use the whole document.
-  return ComputeValueInternal(NS_LITERAL_STRING("text/plain"), aFlags, aResult);
+  nsresult rv =
+      ComputeValueInternal(NS_LITERAL_STRING("text/plain"), aFlags, aResult);
+  NS_WARNING_ASSERTION(NS_SUCCEEDED(rv), "ComputeValueInternal() failed");
+  return rv;
 }
 
 void TextEditor::OnStartToHandleTopLevelEditSubAction(
diff --git a/editor/libeditor/TextEditor.h b/editor/libeditor/TextEditor.h
index 51ad02815324..b042da07fb99 100644
--- a/editor/libeditor/TextEditor.h
+++ b/editor/libeditor/TextEditor.h
@@ -650,6 +650,16 @@ class TextEditor : public EditorBase,
   HandleDeleteSelection(nsIEditor::EDirection aDirectionAndAmount,
                         nsIEditor::EStripWrappers aStripWrappers);
 
+  /**
+   * ComputeValueFromTextNodeAndPaddingBRElement() tries to compute "value" of
+   * this editor content only with text node and padding `<br>` element.
+   * If this succeeds to compute the value, it's returned with aValue and
+   * the result is marked as "handled".  Otherwise, the caller needs to
+   * compute it with another way.
+   */
+  EditActionResult ComputeValueFromTextNodeAndPaddingBRElement(
+      nsAString& aValue) const;
+
  protected:  // Called by helper classes.
   virtual void OnStartToHandleTopLevelEditSubAction(
       EditSubAction aEditSubAction, nsIEditor::EDirection aDirection) override;
@@ -821,7 +831,7 @@ class TextEditor : public EditorBase,
    * string.
    */
   nsresult SharedOutputString(uint32_t aFlags, bool* aIsCollapsed,
-                              nsAString& aResult);
+                              nsAString& aResult) const;
 
   /**
    * See comment of IsCopyToClipboardAllowed() for the detail.