Don't allow protected content for edge-extension

While this should be logically ok, in practice, edge-extension
currently operates by taking a screenshot and operating on the
bitmap. This isn't supported for protected content so, for now,
just skip it.

Bug: 291881865
Test: open settings via 3-dot menu while google-tv video is
      playing.
Change-Id: Iaa800e19508c5801c2b75c8fb636d8784b2ea0b6