Fix behavior of stencil clipping within clearLayerRegions

bug:16376960

The draw within clearLayerRegions should never be affected by the
current stencil clip, since it's just ensuring that the content of the
layer is cleared, and not doing real content drawing.

Also, add optional verbose GL event logging

Change-Id: I538b1bc631fc091340b76e12db6af0c219851b57
diff --git a/libs/hwui/Debug.h b/libs/hwui/Debug.h
index d6dc6ad..5808aac 100644
--- a/libs/hwui/Debug.h
+++ b/libs/hwui/Debug.h
@@ -82,6 +82,9 @@
 // Turn on to insert an event marker for each display list op
 #define DEBUG_DISPLAY_LIST_OPS_AS_EVENTS 0
 
+// Turn on to insert detailed event markers
+#define DEBUG_DETAILED_EVENTS 0
+
 // Turn on to highlight drawing batches and merged batches with different colors
 #define DEBUG_MERGE_BEHAVIOR 0