Bug 835015 - Enable png_set_keep_unknown_chunks on Gonk, r=glennrp

media/libpng/mozpngconf.h

@@ -46,6 +46,7 @@
 /* necessary for boot animation code */
 #ifdef MOZ_WIDGET_GONK
 #define PNG_EASY_ACCESS_SUPPORTED
+#define PNG_HANDLE_AS_UNKNOWN_SUPPORTED
 #define PNG_READ_BGR_SUPPORTED
 #define PNG_READ_EXPAND_SUPPORTED
 #define PNG_READ_FILLER_SUPPORTED