C-ify DataSource

Add a C API for DataSource/Base, and a helper so extractors
can continue using a C++ API.

Bug: 111407253
Test: build, boot, play some files

Change-Id: I1c8b2990e17d18eee53c9abf7ebef2ced0e8b7fd
diff --git a/media/extractors/mp3/XINGSeeker.cpp b/media/extractors/mp3/XINGSeeker.cpp
index 01e06ca..9f1fd7a 100644
--- a/media/extractors/mp3/XINGSeeker.cpp
+++ b/media/extractors/mp3/XINGSeeker.cpp
@@ -21,7 +21,9 @@
 #include <media/stagefright/foundation/avc_utils.h>
 
 #include <media/stagefright/foundation/ByteUtils.h>
-#include <media/DataSourceBase.h>
+
+#include <media/MediaExtractorPluginApi.h>
+#include <media/MediaExtractorPluginHelper.h>
 
 namespace android {
 
@@ -79,7 +81,7 @@
 
 // static
 XINGSeeker *XINGSeeker::CreateFromSource(
-        DataSourceBase *source, off64_t first_frame_pos) {
+        DataSourceHelper *source, off64_t first_frame_pos) {
 
     uint8_t buffer[4];
     int offset = first_frame_pos;