Don't check the visibility of the source in intersectsAnyInsets

The method and the calling methods are for deciding if a window can
control the appearance of the system bar. The window shouldn't lose
control just because the insets source is hidden.

Fix: 376821209
Flag: EXEMPT bugfix
Test: 1. Open a light theme app which can enter immersive mode
         (ex: Docs).
      2. Enter immersive mode (ex: by scrolling a doc in Docs).
      3. Make sure the system bar icon color remain the same.
         (check both status bar and 3-button navigation bar)
Change-Id: I109603e693da4022a578a4d21f6f28912c744a12