Return the correct bigram frequency

The "correct" bigram frequency is now returned by the reading
code. However, as the binary format represents the frequency
in a lossy manner, the frequency is not guaranteed to be the
exact same as the one in the source text format - only a close
enough value. It is however the exact same value seen by the
native code.

Bug: 7395653
Change-Id: I49199ef18901c671189912b3550623e9643baedd