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/VBRISeeker.cpp b/media/extractors/mp3/VBRISeeker.cpp
index 523f14c..9eb72a7 100644
--- a/media/extractors/mp3/VBRISeeker.cpp
+++ b/media/extractors/mp3/VBRISeeker.cpp
@@ -27,7 +27,9 @@
 
 #include <media/stagefright/foundation/ADebug.h>
 #include <media/stagefright/foundation/ByteUtils.h>
-#include <media/DataSourceBase.h>
+
+#include <media/MediaExtractorPluginApi.h>
+#include <media/MediaExtractorPluginHelper.h>
 
 namespace android {
 
@@ -37,7 +39,7 @@
 
 // static
 VBRISeeker *VBRISeeker::CreateFromSource(
-        DataSourceBase *source, off64_t post_id3_pos) {
+        DataSourceHelper *source, off64_t post_id3_pos) {
     off64_t pos = post_id3_pos;
 
     uint8_t header[4];