Mark protected IndexPager properties also as protected in subclasses

Mark protected IndexPager properties also as protected in subclasses

I'm intentionally only touching these protected properties and nothing
else, because I believe these are uncontroversial. They should be protected
according to modern SOLID standards, and actually are declared as
protected in the base class. What this patch effectively does is documenting
this fact, but it does not change anything.

Change-Id: I625307b58bd419c4a72e9842b2b46c08ed9b4f8e