Trim OpenGLRenderer's memory usage whenever possible

Change-Id: I9225077184f374b1a43300add15cc1d5b6869d1c
diff --git a/libs/hwui/Debug.h b/libs/hwui/Debug.h
index 2cdc8c3..5db73db 100644
--- a/libs/hwui/Debug.h
+++ b/libs/hwui/Debug.h
@@ -26,6 +26,9 @@
 // Turn on to enable memory usage summary on each frame
 #define DEBUG_MEMORY_USAGE 0
 
+// Turn on to enable debugging of cache flushes
+#define DEBUG_CACHE_FLUSH 1
+
 // Turn on to enable layers debugging when rendered as regions
 #define DEBUG_LAYERS_AS_REGIONS 0