Bug 1940377 - part 4: Make HTMLEditor normalize white-spaces before inserting HTML fragment if the new normalizer is enabled r=m_kato

Unfortunately, this change does not make
`white-spaces-after-insert-image.tentative.html?paste-image` pass because we
paste the `<div>` at pasting the `<img>`, but Chrome pastes only the `<img>`.

Differential Revision: https://phabricator.services.mozilla.com/D239466

editor/libeditor/HTMLEditSubActionHandler.cpp

@@ -561,11 +561,10 @@ nsresult HTMLEditor::OnEndHandlingTopLevelEditSubActionInternal() {
         case EditSubAction::eInsertTextComingFromIME:
         case EditSubAction::eInsertLineBreak:
         case EditSubAction::eInsertParagraphSeparator:
-          return !StaticPrefs::
-              editor_white_space_normalization_blink_compatible();
         case EditSubAction::ePasteHTMLContent:
         case EditSubAction::eInsertHTMLSource:
-          return true;
+          return !StaticPrefs::
+              editor_white_space_normalization_blink_compatible();
         default:
           return false;
       }