Fixes bug 2502132, and masks bug 2518313.

Change-Id: I5c5ecf1c10763f7b3f3d1e5c57dc5ce77cc344fd
diff --git a/media/libstagefright/AMRExtractor.cpp b/media/libstagefright/AMRExtractor.cpp
index 2a16d26..0fea72e 100644
--- a/media/libstagefright/AMRExtractor.cpp
+++ b/media/libstagefright/AMRExtractor.cpp
@@ -222,7 +222,7 @@
     ssize_t n = mDataSource->readAt(mOffset, &header, 1);
 
     if (n < 1) {
-        return ERROR_IO;
+        return ERROR_END_OF_STREAM;
     }
 
     if (header & 0x83) {