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/ItemTable.h b/media/extractors/mp4/ItemTable.h
index 536dcb0..650b3f3 100644
--- a/media/extractors/mp4/ItemTable.h
+++ b/media/extractors/mp4/ItemTable.h
@@ -25,7 +25,7 @@
 
 namespace android {
 
-class DataSourceBase;
+class DataSourceHelper;
 class MetaData;
 
 namespace heif {
@@ -45,7 +45,7 @@
 
 class ItemTable : public RefBase {
 public:
-    explicit ItemTable(DataSourceBase *source);
+    explicit ItemTable(DataSourceHelper *source);
 
     status_t parse(uint32_t type, off64_t offset, size_t size);
 
@@ -62,7 +62,7 @@
     ~ItemTable();
 
 private:
-    DataSourceBase *mDataSource;
+    DataSourceHelper *mDataSource;
 
     KeyedVector<uint32_t, ItemLoc> mItemLocs;
     Vector<ItemInfo> mItemInfos;