--- a/dom/html/HTMLInputElement.cpp
+++ b/dom/html/HTMLInputElement.cpp
@@ -7398,23 +7398,16 @@ HTMLInputElement::IsSingleLineTextContro
 
 NS_IMETHODIMP_(bool)
 HTMLInputElement::IsTextArea() const
 {
   return false;
 }
 
 NS_IMETHODIMP_(bool)
-HTMLInputElement::IsPlainTextControl() const
-{
-  // need to check our HTML attribute and/or CSS.
-  return true;
-}
-
-NS_IMETHODIMP_(bool)
 HTMLInputElement::IsPasswordTextControl() const
 {
   return mType == NS_FORM_INPUT_PASSWORD;
 }
 
 NS_IMETHODIMP_(int32_t)
 HTMLInputElement::GetCols()
 {

--- a/dom/html/HTMLInputElement.h
+++ b/dom/html/HTMLInputElement.h
@@ -228,17 +228,16 @@ private:
   virtual void RemoveStates(EventStates aStates) override;
 
 public:
 
   // nsITextControlElement
   NS_IMETHOD SetValueChanged(bool aValueChanged) override;
   NS_IMETHOD_(bool) IsSingleLineTextControl() const override;
   NS_IMETHOD_(bool) IsTextArea() const override;
-  NS_IMETHOD_(bool) IsPlainTextControl() const override;
   NS_IMETHOD_(bool) IsPasswordTextControl() const override;
   NS_IMETHOD_(int32_t) GetCols() override;
   NS_IMETHOD_(int32_t) GetWrapCols() override;
   NS_IMETHOD_(int32_t) GetRows() override;
   NS_IMETHOD_(void) GetDefaultValueFromContent(nsAString& aValue) override;
   NS_IMETHOD_(bool) ValueChanged() const override;
   NS_IMETHOD_(void) GetTextEditorValue(nsAString& aValue, bool aIgnoreWrap) const override;
   NS_IMETHOD_(mozilla::TextEditor*) GetTextEditor() override;

--- a/dom/html/HTMLTextAreaElement.cpp
+++ b/dom/html/HTMLTextAreaElement.cpp
@@ -1326,23 +1326,16 @@ HTMLTextAreaElement::IsSingleLineTextCon
 
 NS_IMETHODIMP_(bool)
 HTMLTextAreaElement::IsTextArea() const
 {
   return true;
 }
 
 NS_IMETHODIMP_(bool)
-HTMLTextAreaElement::IsPlainTextControl() const
-{
-  // need to check our HTML attribute and/or CSS.
-  return true;
-}
-
-NS_IMETHODIMP_(bool)
 HTMLTextAreaElement::IsPasswordTextControl() const
 {
   return false;
 }
 
 NS_IMETHODIMP_(int32_t)
 HTMLTextAreaElement::GetCols()
 {

--- a/dom/html/HTMLTextAreaElement.h
+++ b/dom/html/HTMLTextAreaElement.h
@@ -84,17 +84,16 @@ public:
   virtual void FieldSetDisabledChanged(bool aNotify) override;
 
   virtual EventStates IntrinsicState() const override;
 
   // nsITextControlElemet
   NS_IMETHOD SetValueChanged(bool aValueChanged) override;
   NS_IMETHOD_(bool) IsSingleLineTextControl() const override;
   NS_IMETHOD_(bool) IsTextArea() const override;
-  NS_IMETHOD_(bool) IsPlainTextControl() const override;
   NS_IMETHOD_(bool) IsPasswordTextControl() const override;
   NS_IMETHOD_(int32_t) GetCols() override;
   NS_IMETHOD_(int32_t) GetWrapCols() override;
   NS_IMETHOD_(int32_t) GetRows() override;
   NS_IMETHOD_(void) GetDefaultValueFromContent(nsAString& aValue) override;
   NS_IMETHOD_(bool) ValueChanged() const override;
   NS_IMETHOD_(void) GetTextEditorValue(nsAString& aValue, bool aIgnoreWrap) const override;
   NS_IMETHOD_(mozilla::TextEditor*) GetTextEditor() override;

--- a/dom/html/nsITextControlElement.h
+++ b/dom/html/nsITextControlElement.h
@@ -52,22 +52,16 @@ public:
 
   /**
    * Find out whether this control is a textarea.
    * @return whether this is a textarea text control
    */
   NS_IMETHOD_(bool) IsTextArea() const = 0;
 
   /**
-   * Find out whether this control edits plain text.  (Currently always true.)
-   * @return whether this is a plain text control
-   */
-  NS_IMETHOD_(bool) IsPlainTextControl() const = 0;
-
-  /**
    * Find out whether this is a password control (input type=password)
    * @return whether this is a password ontrol
    */
   NS_IMETHOD_(bool) IsPasswordTextControl() const = 0;
 
   /**
    * Get the cols attribute (if textarea) or a default
    * @return the number of columns to use

--- a/dom/html/nsTextEditorState.cpp
+++ b/dom/html/nsTextEditorState.cpp
@@ -1415,19 +1415,17 @@ nsTextEditorState::PrepareEditor(const n
   // Note that we don't check mTextEditor here, because we might already have
   // one around, in which case we don't create a new one, and we'll just tie
   // the required machinery to it.
 
   nsPresContext *presContext = mBoundFrame->PresContext();
   nsIPresShell *shell = presContext->GetPresShell();
 
   // Setup the editor flags
-  uint32_t editorFlags = 0;
-  if (IsPlainTextControl())
-    editorFlags |= nsIPlaintextEditor::eEditorPlaintextMask;
+  uint32_t editorFlags = nsIPlaintextEditor::eEditorPlaintextMask;
   if (IsSingleLineTextControl())
     editorFlags |= nsIPlaintextEditor::eEditorSingleLineMask;
   if (IsPasswordTextControl())
     editorFlags |= nsIPlaintextEditor::eEditorPasswordMask;
 
   // All nsTextControlFrames are widgets
   editorFlags |= nsIPlaintextEditor::eEditorWidgetMask;
 
@@ -2442,23 +2440,18 @@ nsTextEditorState::GetValue(nsAString& a
       aValue = mCachedValue;
       return;
     }
 
     aValue.Truncate(); // initialize out param
 
     uint32_t flags = (nsIDocumentEncoder::OutputLFLineBreak |
                       nsIDocumentEncoder::OutputPreformatted |
-                      nsIDocumentEncoder::OutputPersistNBSP);
-
-    if (IsPlainTextControl())
-    {
-      flags |= nsIDocumentEncoder::OutputBodyOnly;
-    }
-
+                      nsIDocumentEncoder::OutputPersistNBSP |
+                      nsIDocumentEncoder::OutputBodyOnly);
     if (!aIgnoreWrap) {
       nsITextControlElement::nsHTMLTextWrap wrapProp;
       nsCOMPtr<nsIContent> content = do_QueryInterface(mTextCtrlElement);
       if (content &&
           nsITextControlElement::GetWrapPropertyEnum(content, wrapProp) &&
           wrapProp == nsITextControlElement::eHTMLTextWrap_Hard) {
         flags |= nsIDocumentEncoder::OutputWrap;
       }

--- a/dom/html/nsTextEditorState.h
+++ b/dom/html/nsTextEditorState.h
@@ -215,19 +215,16 @@ public:
   }
 
   bool IsSingleLineTextControl() const {
     return mTextCtrlElement->IsSingleLineTextControl();
   }
   bool IsTextArea() const {
     return mTextCtrlElement->IsTextArea();
   }
-  bool IsPlainTextControl() const {
-    return mTextCtrlElement->IsPlainTextControl();
-  }
   bool IsPasswordTextControl() const {
     return mTextCtrlElement->IsPasswordTextControl();
   }
   int32_t GetCols() {
     return mTextCtrlElement->GetCols();
   }
   int32_t GetWrapCols() {
     return mTextCtrlElement->GetWrapCols();

--- a/layout/forms/nsTextControlFrame.h
+++ b/layout/forms/nsTextControlFrame.h
@@ -201,17 +201,16 @@ public: //for methods who access nsTextC
   type name() const {                                                          \
     nsCOMPtr<nsITextControlElement> txtCtrl = do_QueryInterface(GetContent()); \
     NS_ASSERTION(txtCtrl, "Content not a text control element");               \
     return txtCtrl->name();                                                    \
   }
 
   DEFINE_TEXTCTRL_CONST_FORWARDER(bool, IsSingleLineTextControl)
   DEFINE_TEXTCTRL_CONST_FORWARDER(bool, IsTextArea)
-  DEFINE_TEXTCTRL_CONST_FORWARDER(bool, IsPlainTextControl)
   DEFINE_TEXTCTRL_CONST_FORWARDER(bool, IsPasswordTextControl)
   DEFINE_TEXTCTRL_CONST_FORWARDER(int32_t, GetCols)
   DEFINE_TEXTCTRL_CONST_FORWARDER(int32_t, GetWrapCols)
   DEFINE_TEXTCTRL_CONST_FORWARDER(int32_t, GetRows)
 
 #undef DEFINE_TEXTCTRL_CONST_FORWARDER
 #undef DEFINE_TEXTCTRL_FORWARDER