[MOD] Use Cronet from Play Services, as default instead of using embedded one.…

[MOD] Use Cronet from Play Services, as default instead of using embedded one. It lets to reduce APK size ~8MB.

extensions/cronet/src/test/java/com/google/android/exoplayer2/ext/cronet/CronetDataSourceTest.java

@@ -156,7 +156,7 @@ public final class CronetDataSourceTest {
 
       @Override
       public List<String> getUrlChain() {
-        return null;
+        return Collections.singletonList(url);
       }
 
       @Override