Migrate libmediandk to ndk_library.

Test: make native
Bug: http://b/30465923
Change-Id: Id62eac2d5cc518465445d87ce204fa918f0ddb68
diff --git a/include/ndk/NdkImageReader.h b/include/ndk/NdkImageReader.h
index 7c7ec6a..8d72c28 100644
--- a/include/ndk/NdkImageReader.h
+++ b/include/ndk/NdkImageReader.h
@@ -36,6 +36,8 @@
 #ifndef _NDK_IMAGE_READER_H
 #define _NDK_IMAGE_READER_H
 
+#include <sys/cdefs.h>
+
 #include <android/native_window.h>
 #include "NdkMediaError.h"
 #include "NdkImage.h"
@@ -44,6 +46,8 @@
 extern "C" {
 #endif
 
+#if __ANDROID_API__ >= 24
+
 /**
  * AImage is an opaque type that allows direct application access to image data rendered into a
  * {@link ANativeWindow}.
@@ -294,6 +298,8 @@
 media_status_t AImageReader_setImageListener(
         AImageReader* reader, AImageReader_ImageListener* listener);
 
+#endif /* __ANDROID_API__ >= 24 */
+
 #ifdef __cplusplus
 } // extern "C"
 #endif