SF: Reduce resync samples without present

Reduces the number of resync samples that DispSync will attempt to
collect without an intervening present from 12 to 4. The former value
was causing excessive power draw for some vendors' implementations, and
reducing it doesn't seem to harm anything.

Bug: 20724456
Change-Id: Ifd6e0490be67756ed001d509a38e8a36953b4618

services/surfaceflinger/DispSync.h

@@ -139,7 +139,7 @@ private:
     enum { MAX_RESYNC_SAMPLES = 32 };
     enum { MIN_RESYNC_SAMPLES_FOR_UPDATE = 3 };
     enum { NUM_PRESENT_SAMPLES = 8 };
-    enum { MAX_RESYNC_SAMPLES_WITHOUT_PRESENT = 12 };
+    enum { MAX_RESYNC_SAMPLES_WITHOUT_PRESENT = 4 };
 
     // mPeriod is the computed period of the modeled vsync events in
     // nanoseconds.