Prints one histogram of all data in recent history

A call to dumpsys media.log causes the program to read
timestamp data from the circular buffer stored in local memory
to a local data structure which stores this data in a
compressed format.

The current code is a temporary step towards the ultimate
goal (described below). The timestamp data is turned into
historgrams of a small, fixed size, and added to a vector
of histograms. When the vector reaches a given number of
histograms, the oldest one is popped. When dump() is called,
all the short histograms are combined into one large one and
printed. The advantage of this approach is to not delete
data from memory until it is overwritten. Ultimately, this
data structure should be a circular buffer. A second data
structure should be added which keeps a more long-term analysis
of the data.

Test: dumpsys media.log

Change-Id: I39c4818e7d1221d5023a4355b8b57fadd9451de5