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/mp4/SampleTable.cpp b/media/extractors/mp4/SampleTable.cpp
index 28fe717..d242798 100644
--- a/media/extractors/mp4/SampleTable.cpp
+++ b/media/extractors/mp4/SampleTable.cpp
@@ -25,7 +25,7 @@
 
 #include <arpa/inet.h>
 
-#include <media/DataSourceBase.h>
+#include <media/MediaExtractorPluginApi.h>
 #include <media/stagefright/foundation/ADebug.h>
 #include <media/stagefright/foundation/ByteUtils.h>
 
@@ -114,7 +114,7 @@
 
 ////////////////////////////////////////////////////////////////////////////////
 
-SampleTable::SampleTable(DataSourceBase *source)
+SampleTable::SampleTable(DataSourceHelper *source)
     : mDataSource(source),
       mChunkOffsetOffset(-1),
       mChunkOffsetType(0),