Propagate defaultRequestProperties + make getDefaultRequestProperties final

library/src/main/java/com/google/android/exoplayer2/upstream/DefaultHttpDataSourceFactory.java

@@ -79,7 +79,7 @@ public final class DefaultHttpDataSourceFactory extends BaseFactory {
   protected DefaultHttpDataSource createDataSourceInternal(
       HttpDataSource.RequestProperties defaultRequestProperties) {
     return new DefaultHttpDataSource(userAgent, null, listener, connectTimeoutMillis,
-        readTimeoutMillis, allowCrossProtocolRedirects, getDefaultRequestProperties());
+        readTimeoutMillis, allowCrossProtocolRedirects, defaultRequestProperties);
   }
 
 }

library/src/main/java/com/google/android/exoplayer2/upstream/HttpDataSource.java

@@ -177,7 +177,7 @@ public interface HttpDataSource extends DataSource {
     }
 
     @Override
-    public RequestProperties getDefaultRequestProperties() {
+    public final RequestProperties getDefaultRequestProperties() {
       return defaultRequestProperties;
     }