Fix thread priorities.

Graphics ran a display priority.  Compute should run at a lower
priority.

Change-Id: I72055eeb2b62813d3b1d17f2d8e863b178019c8f
diff --git a/rsInternalDefines.h b/rsInternalDefines.h
index 678e6c8..81c13b5 100644
--- a/rsInternalDefines.h
+++ b/rsInternalDefines.h
@@ -198,6 +198,13 @@
 } RsFileIndexEntry;
 
 
+enum RsThreadPriorities {
+    RS_THREAD_PRIORITY_LOW = 15,
+    RS_THREAD_PRIORITY_NORMAL_GRAPHICS = -8,
+    RS_THREAD_PRIORITY_NORMAL = -1,
+    RS_THREAD_PRIORITY_LOW_LATENCY = -4
+};
+
 
 // Structure for rs.spec functions