frameworks/base: Add rendering statistics to Stagefright

Rendering statistics can be enabled by setting the property setprop
persist.debug.sf.statistics to 1. To disable, set the property to 0.

This adds the following logs:
-Clip type and duration
-Number of frames read by parser
-Number of key frames read by parser
-Number of frames dropped
-Number of frames rendered
-First frame latency
-Seek position and latency after seek
-Pause position
-Expected frames per second
-Real time delta of video if it's ahead or behind
-Maximum time delta of video if it's ahead or behind
-Number of occurrences of A/V sync loss
-Maximum time of A/V sync loss

Change-Id: I3eb9abffb71d3325a88f4bdbbef3f78bd675b056