improve SurfaceFlinger dumpsys

It is now possible to say:

dumpsys SurfaceFlinger --latency

to print latency information about all windows

dumpsys SurfaceFlinger --latency window-name

to print the latency stats of the specified window

for instance: dumpsys SurfaceFlinger --latency SurfaceView

The data consists of one line containing global stats, followed by
128 lines of tab separated timestamps in nanosecond.

The first line currently contains the refresh period in nanosecond.
Each 128 following line contains 3 timestamps, of respectively
the app draw time, the vsync timestamp just prior the call to set and
the timestamp of the call to set.

Change-Id: Ib6b6da1d7e2e6ba49c282bdbc0b56a7dc203343a