Separate enable/disable and show/hide logic in ButtonManager

Show/hide occurs during module init, and should not be overridden
during operation when buttons are enabled/disabled. Rather than
make all enabling code handle the complexity of button visibility,
this change just configures buttons to be visible once. Addresses
bug where flash button becomes visible on devices without flash
when toggling HDR, due to logic that enables/disables flash and
HDR together.

Bug: 18376973
Change-Id: I787858ccde1fed9833fd24ac51d3b0bd3cc90df7
2 files changed