Use String8/16 c_str [media]

Bug: 295394788
Test: make checkbuild
Change-Id: I4ba5400f39c769bec59508525844f1daefe1d15c
diff --git a/media/libdatasource/DataSourceFactory.cpp b/media/libdatasource/DataSourceFactory.cpp
index f91e3ea..81a6cd0 100644
--- a/media/libdatasource/DataSourceFactory.cpp
+++ b/media/libdatasource/DataSourceFactory.cpp
@@ -92,7 +92,7 @@
 
         source = NuCachedSource2::Create(
                 mediaHTTP,
-                cacheConfig.isEmpty() ? NULL : cacheConfig.string(),
+                cacheConfig.isEmpty() ? NULL : cacheConfig.c_str(),
                 disconnectAtHighwatermark);
     } else if (!strncasecmp("data:", uri, 5)) {
         source = DataURISource::Create(uri);