Prettify display lists logging

This change makes it a lot easier to see the tree structure.

Change-Id: I4969abd1eb010f1d529671f8d86dc4c930be24f6
diff --git a/libs/hwui/DisplayList.h b/libs/hwui/DisplayList.h
index 86c9ec0..4d1fcb3 100644
--- a/libs/hwui/DisplayList.h
+++ b/libs/hwui/DisplayList.h
@@ -17,6 +17,10 @@
 #ifndef ANDROID_HWUI_DISPLAY_LIST_H
 #define ANDROID_HWUI_DISPLAY_LIST_H
 
+#ifndef LOG_TAG
+    #define LOG_TAG "OpenGLRenderer"
+#endif
+
 #include <SkCamera.h>
 #include <SkMatrix.h>