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
diff --git a/services/surfaceflinger/LayerBase.h b/services/surfaceflinger/LayerBase.h
index 0c1b228..03d2cc6 100644
--- a/services/surfaceflinger/LayerBase.h
+++ b/services/surfaceflinger/LayerBase.h
@@ -211,6 +211,7 @@
     /** always call base class first */
     virtual void dump(String8& result, char* scratch, size_t size) const;
     virtual void shortDump(String8& result, char* scratch, size_t size) const;
+    virtual void dumpStats(String8& result, char* buffer, size_t SIZE) const;
 
 
     enum { // flags for doTransaction()