Remove almost-all android::Singleton users

Bug: 25426213
Change-Id: I88e6206e8915cce95c3a8a8a82a4bb8fbf668141
diff --git a/libs/hwui/Extensions.cpp b/libs/hwui/Extensions.cpp
index 06c8a21..6dd29ad 100644
--- a/libs/hwui/Extensions.cpp
+++ b/libs/hwui/Extensions.cpp
@@ -20,6 +20,7 @@
 #include "Properties.h"
 #include "utils/StringUtils.h"
 
+#include <GLES2/gl2.h>
 #include <GLES2/gl2ext.h>
 #include <utils/Log.h>