Don't draw fully transparent views/primitives.

Change-Id: Icd7d8ef1f57b51a24faf32f7004125e6300d4fdc
diff --git a/libs/hwui/ProgramCache.h b/libs/hwui/ProgramCache.h
index 964d842..ec9851e 100644
--- a/libs/hwui/ProgramCache.h
+++ b/libs/hwui/ProgramCache.h
@@ -45,7 +45,7 @@
 #endif
 
 // TODO: This should be set in properties
-#define PANEL_BIT_DEPTH 18
+#define PANEL_BIT_DEPTH 20
 #define COLOR_COMPONENT_THRESHOLD (1.0f - (0.5f / PANEL_BIT_DEPTH))
 #define COLOR_COMPONENT_INV_THRESHOLD (0.5f / PANEL_BIT_DEPTH)