Adds remaining missing overrides and nullptr usages, missed due to
an extreme failure in tool usage.
Change-Id: I56abd72975a3999ad13330003c348db40f59aebf
Bug #9316260
The GL specification indicates that deleting a bound texture has
the side effect of binding the default texture (name=0). This change
replaces all calls to glDeleteTextures() by Caches::deleteTexture()
to properly keep track of texture bindings.
Change-Id: Ifbc60ef433e0f9776a668dd5bd5f0adbc65a77a0
