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.h b/media/extractors/mp4/SampleTable.h
index dd68860..d4b5dc8 100644
--- a/media/extractors/mp4/SampleTable.h
+++ b/media/extractors/mp4/SampleTable.h
@@ -21,18 +21,19 @@
 #include <sys/types.h>
 #include <stdint.h>
 
+#include <media/MediaExtractorPluginHelper.h>
 #include <media/stagefright/MediaErrors.h>
 #include <utils/RefBase.h>
 #include <utils/threads.h>
 
 namespace android {
 
-class DataSourceBase;
+class DataSourceHelper;
 struct SampleIterator;
 
 class SampleTable : public RefBase {
 public:
-    explicit SampleTable(DataSourceBase *source);
+    explicit SampleTable(DataSourceHelper *source);
 
     bool isValid() const;
 
@@ -102,7 +103,7 @@
     // Limit the total size of all internal tables to 200MiB.
     static const size_t kMaxTotalSize = 200 * (1 << 20);
 
-    DataSourceBase *mDataSource;
+    DataSourceHelper *mDataSource;
     Mutex mLock;
 
     off64_t mChunkOffsetOffset;