diff --git a/editor/libeditor/EditorBase.cpp b/editor/libeditor/EditorBase.cpp
index fb2f2f4c2d01..f4d84cb28e53 100644
--- a/editor/libeditor/EditorBase.cpp
+++ b/editor/libeditor/EditorBase.cpp
@@ -94,6 +94,7 @@
 #include "nsGkAtoms.h"                 // for nsGkAtoms, nsGkAtoms::dir
 #include "nsIClipboard.h"              // for nsIClipboard
 #include "nsIContent.h"                // for nsIContent
+#include "nsIDocumentEncoder.h"        // for nsIDocumentEncoder
 #include "nsIDocumentStateListener.h"  // for nsIDocumentStateListener
 #include "nsIEditActionListener.h"     // for nsIEditActionListener
 #include "nsIEditorObserver.h"         // for nsIEditorObserver
@@ -214,6 +215,7 @@ NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(EditorBase)
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mDocStateListeners)
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mEventTarget)
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mPlaceholderTransaction)
+  NS_IMPL_CYCLE_COLLECTION_UNLINK(mCachedDocumentEncoder)
   NS_IMPL_CYCLE_COLLECTION_UNLINK_WEAK_REFERENCE
 NS_IMPL_CYCLE_COLLECTION_UNLINK_END
 
@@ -239,6 +241,7 @@ NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(EditorBase)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mEventTarget)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mEventListener)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mPlaceholderTransaction)
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mCachedDocumentEncoder)
 NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
 
 NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(EditorBase)
@@ -1408,6 +1411,77 @@ NS_IMETHODIMP EditorBase::SetDocumentCharacterSet(
   return NS_ERROR_NOT_AVAILABLE;
 }
 
+already_AddRefed<nsIDocumentEncoder> EditorBase::GetAndInitDocEncoder(
+    const nsAString& aFormatType, uint32_t aDocumentEncoderFlags,
+    const nsACString& aCharset) const {
+  MOZ_ASSERT(IsEditActionDataAvailable());
+
+  nsCOMPtr<nsIDocumentEncoder> docEncoder;
+  if (!mCachedDocumentEncoder ||
+      !mCachedDocumentEncoderType.Equals(aFormatType)) {
+    nsAutoCString formatType;
+    LossyAppendUTF16toASCII(aFormatType, formatType);
+    docEncoder = do_createDocumentEncoder(PromiseFlatCString(formatType).get());
+    if (NS_WARN_IF(!docEncoder)) {
+      return nullptr;
+    }
+    mCachedDocumentEncoder = docEncoder;
+    mCachedDocumentEncoderType = aFormatType;
+  } else {
+    docEncoder = mCachedDocumentEncoder;
+  }
+
+  RefPtr<Document> doc = GetDocument();
+  NS_ASSERTION(doc, "Need a document");
+
+  nsresult rv = docEncoder->NativeInit(
+      doc, aFormatType,
+      aDocumentEncoderFlags | nsIDocumentEncoder::RequiresReinitAfterOutput);
+  if (NS_FAILED(rv)) {
+    NS_WARNING("nsIDocumentEncoder::NativeInit() failed");
+    return nullptr;
+  }
+
+  if (!aCharset.IsEmpty() && !aCharset.EqualsLiteral("null")) {
+    DebugOnly<nsresult> rvIgnored = docEncoder->SetCharset(aCharset);
+    NS_WARNING_ASSERTION(
+        NS_SUCCEEDED(rvIgnored),
+        "nsIDocumentEncoder::SetCharset() failed, but ignored");
+  }
+
+  const int32_t wrapWidth = std::max(WrapWidth(), 0);
+  DebugOnly<nsresult> rvIgnored = docEncoder->SetWrapColumn(wrapWidth);
+  NS_WARNING_ASSERTION(
+      NS_SUCCEEDED(rvIgnored),
+      "nsIDocumentEncoder::SetWrapColumn() failed, but ignored");
+
+  // Set the selection, if appropriate.
+  // We do this either if the OutputSelectionOnly flag is set,
+  // in which case we use our existing selection ...
+  if (aDocumentEncoderFlags & nsIDocumentEncoder::OutputSelectionOnly) {
+    if (NS_FAILED(docEncoder->SetSelection(&SelectionRef()))) {
+      NS_WARNING("nsIDocumentEncoder::SetSelection() failed");
+      return nullptr;
+    }
+  }
+  // ... or if the root element is not a body,
+  // in which case we set the selection to encompass the root.
+  else {
+    Element* rootElement = GetRoot();
+    if (NS_WARN_IF(!rootElement)) {
+      return nullptr;
+    }
+    if (!rootElement->IsHTMLElement(nsGkAtoms::body)) {
+      if (NS_FAILED(docEncoder->SetContainerNode(rootElement))) {
+        NS_WARNING("nsIDocumentEncoder::SetContainerNode() failed");
+        return nullptr;
+      }
+    }
+  }
+
+  return docEncoder.forget();
+}
+
 bool EditorBase::AreClipboardCommandsUnconditionallyEnabled() const {
   Document* document = GetDocument();
   return document && document->AreClipboardCommandsUnconditionallyEnabled();
diff --git a/editor/libeditor/EditorBase.h b/editor/libeditor/EditorBase.h
index 63fd260ca0ed..4afe22db01e5 100644
--- a/editor/libeditor/EditorBase.h
+++ b/editor/libeditor/EditorBase.h
@@ -44,6 +44,7 @@ class mozInlineSpellChecker;
 class nsAtom;
 class nsCaret;
 class nsIContent;
+class nsIDocumentEncoder;
 class nsIDocumentStateListener;
 class nsIEditActionListener;
 class nsIEditorObserver;
@@ -2240,6 +2241,19 @@ class EditorBase : public nsIEditor,
    */
   nsresult GetDocumentCharsetInternal(nsACString& aCharset) const;
 
+  /**
+   * GetAndInitDocEncoder() returns a document encoder instance for aFormatType
+   * after initializing it.  The result may be cached for saving recreation
+   * cost.
+   *
+   * @param aFormatType             MIME type like "text/plain".
+   * @param aDocumentEncoderFlags   Flags of nsIDocumentEncoder.
+   * @param aCharset                Encoding of the document.
+   */
+  already_AddRefed<nsIDocumentEncoder> GetAndInitDocEncoder(
+      const nsAString& aFormatType, uint32_t aDocumentEncoderFlags,
+      const nsACString& aCharset) const;
+
   /**
    * SelectAllInternal() should be used instead of SelectAll() in editor
    * because SelectAll() creates AutoEditActionSetter but we should avoid
@@ -2726,6 +2740,12 @@ class EditorBase : public nsIEditor,
 
   RefPtr<IMEContentObserver> mIMEContentObserver;
 
+  // These members cache last encoder and its type for the performance in
+  // TextEditor::ComputeTextValue() which is the implementation of
+  // `<input>.value` and `<textarea>.value`.  See `GetAndInitDocEncoder()`.
+  mutable nsCOMPtr<nsIDocumentEncoder> mCachedDocumentEncoder;
+  mutable nsString mCachedDocumentEncoderType;
+
   // Listens to all low level actions on the doc.
   // Edit action listener is currently used by highlighter of the findbar and
   // the spellchecker.  So, we should reserve only 2 items.
diff --git a/editor/libeditor/TextEditor.cpp b/editor/libeditor/TextEditor.cpp
index b0dfeb037e5f..c8de3974b24b 100644
--- a/editor/libeditor/TextEditor.cpp
+++ b/editor/libeditor/TextEditor.cpp
@@ -95,12 +95,10 @@ NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN_INHERITED(TextEditor, EditorBase)
   if (tmp->mMaskTimer) {
     tmp->mMaskTimer->Cancel();
   }
-  NS_IMPL_CYCLE_COLLECTION_UNLINK(mCachedDocumentEncoder)
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mMaskTimer)
 NS_IMPL_CYCLE_COLLECTION_UNLINK_END
 
 NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN_INHERITED(TextEditor, EditorBase)
-  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mCachedDocumentEncoder)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mMaskTimer)
 NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
 
@@ -480,77 +478,6 @@ bool TextEditor::IsCopyToClipboardAllowedInternal() const {
   return mUnmaskedStart <= selectionStart && UnmaskedEnd() >= selectionEnd;
 }
 
-already_AddRefed<nsIDocumentEncoder> TextEditor::GetAndInitDocEncoder(
-    const nsAString& aFormatType, uint32_t aDocumentEncoderFlags,
-    const nsACString& aCharset) const {
-  MOZ_ASSERT(IsEditActionDataAvailable());
-
-  nsCOMPtr<nsIDocumentEncoder> docEncoder;
-  if (!mCachedDocumentEncoder ||
-      !mCachedDocumentEncoderType.Equals(aFormatType)) {
-    nsAutoCString formatType;
-    LossyAppendUTF16toASCII(aFormatType, formatType);
-    docEncoder = do_createDocumentEncoder(PromiseFlatCString(formatType).get());
-    if (NS_WARN_IF(!docEncoder)) {
-      return nullptr;
-    }
-    mCachedDocumentEncoder = docEncoder;
-    mCachedDocumentEncoderType = aFormatType;
-  } else {
-    docEncoder = mCachedDocumentEncoder;
-  }
-
-  RefPtr<Document> doc = GetDocument();
-  NS_ASSERTION(doc, "Need a document");
-
-  nsresult rv = docEncoder->NativeInit(
-      doc, aFormatType,
-      aDocumentEncoderFlags | nsIDocumentEncoder::RequiresReinitAfterOutput);
-  if (NS_FAILED(rv)) {
-    NS_WARNING("nsIDocumentEncoder::NativeInit() failed");
-    return nullptr;
-  }
-
-  if (!aCharset.IsEmpty() && !aCharset.EqualsLiteral("null")) {
-    DebugOnly<nsresult> rvIgnored = docEncoder->SetCharset(aCharset);
-    NS_WARNING_ASSERTION(
-        NS_SUCCEEDED(rvIgnored),
-        "nsIDocumentEncoder::SetCharset() failed, but ignored");
-  }
-
-  const int32_t wrapWidth = std::max(WrapWidth(), 0);
-  DebugOnly<nsresult> rvIgnored = docEncoder->SetWrapColumn(wrapWidth);
-  NS_WARNING_ASSERTION(
-      NS_SUCCEEDED(rvIgnored),
-      "nsIDocumentEncoder::SetWrapColumn() failed, but ignored");
-
-  // Set the selection, if appropriate.
-  // We do this either if the OutputSelectionOnly flag is set,
-  // in which case we use our existing selection ...
-  if (aDocumentEncoderFlags & nsIDocumentEncoder::OutputSelectionOnly) {
-    if (NS_FAILED(docEncoder->SetSelection(&SelectionRef()))) {
-      NS_WARNING("nsIDocumentEncoder::SetSelection() failed");
-      return nullptr;
-    }
-  }
-  // ... or if the root element is not a body,
-  // in which case we set the selection to encompass the root.
-  else {
-    dom::Element* rootElement = GetRoot();
-    if (NS_WARN_IF(!rootElement)) {
-      return nullptr;
-    }
-    if (!rootElement->IsHTMLElement(nsGkAtoms::body)) {
-      if (NS_FAILED(docEncoder->SetContainerNode(rootElement))) {
-        NS_WARNING("nsIDocumentEncoder::SetContainerNode() failed");
-        return nullptr;
-      }
-    }
-  }
-
-  return docEncoder.forget();
-}
-
 NS_IMETHODIMP TextEditor::OutputToString(const nsAString& aFormatType,
                                          uint32_t aDocumentEncoderFlags,
                                          nsAString& aOutputString) {
@@ -602,7 +529,7 @@ nsresult TextEditor::ComputeValueInternal(const nsAString& aFormatType,
   nsCOMPtr<nsIDocumentEncoder> encoder =
       GetAndInitDocEncoder(aFormatType, aDocumentEncoderFlags, charset);
   if (!encoder) {
-    NS_WARNING("TextEditor::GetAndInitDocEncoder() failed");
+    NS_WARNING("EditorBase::GetAndInitDocEncoder() failed");
     return NS_ERROR_FAILURE;
   }
 
diff --git a/editor/libeditor/TextEditor.h b/editor/libeditor/TextEditor.h
index 7224194cd23b..8ac6b7b0caac 100644
--- a/editor/libeditor/TextEditor.h
+++ b/editor/libeditor/TextEditor.h
@@ -522,19 +522,6 @@ class TextEditor : public EditorBase, public nsITimerCallback, public nsINamed {
    */
   bool IsSafeToInsertData(const Document* aSourceDoc) const;
 
-  /**
-   * GetAndInitDocEncoder() returns a document encoder instance for aFormatType
-   * after initializing it.  The result may be cached for saving recreation
-   * cost.
-   *
-   * @param aFormatType             MIME type like "text/plain".
-   * @param aDocumentEncoderFlags   Flags of nsIDocumentEncoder.
-   * @param aCharset                Encoding of the document.
-   */
-  already_AddRefed<nsIDocumentEncoder> GetAndInitDocEncoder(
-      const nsAString& aFormatType, uint32_t aDocumentEncoderFlags,
-      const nsACString& aCharset) const;
-
   /**
    * ComputeValueInternal() computes string value of this editor for given
    * format.  This may be too expensive if it's in hot path.
@@ -573,14 +560,10 @@ class TextEditor : public EditorBase, public nsITimerCallback, public nsINamed {
                                                      bool aForceStartMasking);
 
  protected:
-  mutable nsCOMPtr<nsIDocumentEncoder> mCachedDocumentEncoder;
-
   // Timer to mask unmasked characters automatically.  Used only when it's
   // a password field.
   nsCOMPtr<nsITimer> mMaskTimer;
 
-  mutable nsString mCachedDocumentEncoderType;
-
   int32_t mMaxTextLength;
 
   // Unmasked character range.  Used only when it's a password field.