Recycle OffscreenBuffers

Change-Id: Ia2e219026f211a5308ecf8209c5f986bb888aadd
diff --git a/libs/hwui/utils/Macros.h b/libs/hwui/utils/Macros.h
index 5ca9083..ccf2287 100644
--- a/libs/hwui/utils/Macros.h
+++ b/libs/hwui/utils/Macros.h
@@ -35,4 +35,7 @@
         static_assert(std::is_standard_layout<Type>::value, \
         #Type " must have standard layout")
 
+#define WARN_UNUSED_RESULT \
+    __attribute__((warn_unused_result))
+
 #endif /* MACROS_H */