Implement AImageDecoder_resultToString

Bug: 160984428
Test: I118eaa99cd65b70dbfb2c8a7731c714564911a34
Change-Id: Iac444b04521056ae6f08cf7bbf12a79a80698c4c
diff --git a/native/graphics/jni/libjnigraphics.map.txt b/native/graphics/jni/libjnigraphics.map.txt
index c8f1151..d8c3cef 100644
--- a/native/graphics/jni/libjnigraphics.map.txt
+++ b/native/graphics/jni/libjnigraphics.map.txt
@@ -1,5 +1,6 @@
 LIBJNIGRAPHICS {
   global:
+    AImageDecoder_resultToString; # introduced=31
     AImageDecoder_createFromAAsset; # introduced=30
     AImageDecoder_createFromFd; # introduced=30
     AImageDecoder_createFromBuffer; # introduced=30