Bug 1551086 - Do not finish edit action when unbinding the frame from the editing state. r=masayuki

The code here was introduced to fix bug 1053048, but the test there and the
test-case there no longer need this, and it's generally unsound to do stuff that
changes the state of the input from UnbindFromFrame().

I'll file a new bug for the bogus disabled styling in the test-case in a second.

I don't know how to add a test for this (no less because the testcase crashes on
debug builds regardless of this patch, see bug 1551192).

Differential Revision: https://phabricator.services.mozilla.com/D30914

--HG--
extra : moz-landing-system : lando

dom/html/nsTextEditorState.cpp

@@ -1930,14 +1930,6 @@ void nsTextEditorState::UnbindFromFrame(nsTextControlFrame* aFrame) {
   MOZ_ASSERT(aFrame == mBoundFrame, "Unbinding from the wrong frame");
   NS_ENSURE_TRUE_VOID(!aFrame || aFrame == mBoundFrame);
 
-  // If the editor is modified but nsIEditorObserver::EditAction() hasn't been
-  // called yet, we need to notify it here because editor may be destroyed
-  // before EditAction() is called if selection listener causes flushing layout.
-  if (mTextListener && mTextEditor && mEditorInitialized &&
-      mTextEditor->IsInEditSubAction()) {
-    mTextListener->OnEditActionHandled();
-  }
-
   // We need to start storing the value outside of the editor if we're not
   // going to use it anymore, so retrieve it for now.
   nsAutoString value;