Histogram-based noise estimation algorithm

Histogram-based noise estimation algorithm

Histogram-based noise estimation algorithm leveraged that low-noise sequences
tend to populate lower-valued histogram bins and high-noise sequences tend to
populate higher-valued histogram bins in a predictable/repeatable manner. The
algorithm compensates for histogram flattening and skewing toward zero as the
scene darkens.

Change-Id: Ia5acb611f0cc6d726280bd5ea5f45d42ff0dc2dd