Bug 1717156 - part 6: Get rid of nsIEditor::eEditorDontEchoPassword r=m_kato

It's used only by password field, i.e., only by `TextEditor`, and used
temporarily.  Additionally, there is some space in `TextEditor`.  So, we
can get rid of it, and make `TextEditor` store it directly.

Note that this allows to skip expensive `nsIEditor::SetFlags()` calls by
`AutoRestoreEditorState`.  This may improve setting `<input>.value` performance.

Differential Revision: https://phabricator.services.mozilla.com/D118266

editor/libeditor/TextEditor.cpp

@@ -75,8 +75,9 @@ TextEditor::TextEditor()
     : mMaxTextLength(-1),
       mUnmaskedStart(UINT32_MAX),
       mUnmaskedLength(0),
-      mIsMaskingPassword(true) {
-  // printf("Size of TextEditor: %zu\n", sizeof(TextEditor));
+      mIsMaskingPassword(true),
+      mEchoingPasswordPrevented(false) {
+  printf("Size of TextEditor: %zu\n", sizeof(TextEditor));
   static_assert(
       sizeof(TextEditor) <= 512,
       "TextEditor instance should be allocatable in the quantum class bins");