See discussion here:

https://chromium-review.googlesource.com/c/chromium/src/+/1060560/1/chrome/android/java/src/org/chromium/chrome/browser/toolbar/ToolbarManager.java#665

"I would rather leave the code as is and have a TODO to refactor it properly.

We just need to pull out an IncognitoToolbarButtonController that owns the TabModelSelector and pokes the IncognitoToolbarButton with the various signals:

hasIncognitoTabs (used in tablet version only) and isIncognitoSelected (used only in the base class).

We should use any of these opportunities to clean up the existing code if you don't want to do it in this CL, file a bug assigned to you and do it in a followup."