Clean up some uses of "auto".

Make actual types more explicit, either by replacing "auto"
with actual type or by assigning std::pair<> elements of
an "auto" variable to typed variables. Avoid binding const
references to temporaries. Avoid copying a container.

Test: m test-art-host-gtest
Change-Id: I1a59f9ba1ee15950cacfc5853bd010c1726de603