Bug 1842027 - Remove nsTextControlFrame::TextEquals. r=masayuki

It is always called from TextControlState, and always ends up in
TextControlState::ValueEquals, so we can avoid some indirection and just
use that.

Depends on D183282

Differential Revision: https://phabricator.services.mozilla.com/D183283

dom/html/HTMLInputElement.cpp

@@ -6774,11 +6774,6 @@ void HTMLInputElement::GetTextEditorValue(nsAString& aValue) const {
   }
 }
 
-bool HTMLInputElement::TextEditorValueEquals(const nsAString& aValue) const {
-  TextControlState* state = GetEditorState();
-  return state ? state->ValueEquals(aValue) : aValue.IsEmpty();
-}
-
 void HTMLInputElement::InitializeKeyboardEventListeners() {
   TextControlState* state = GetEditorState();
   if (state) {