onBatchComplete

To implement the transactional requirement mentioned in the class javadoc, we only commit UI changes to the actual view hierarchy once a batch of JS->Java calls have been completed. We know this is safe because all JS->Java calls that are triggered by a Java->JS call (e.g. the delivery of a touch event or execution of 'renderApplication') end up in a single JS->Java transaction.

A better way to do this would be to have JS explicitly signal to this module when a UI transaction is done. Right now, though, this is how iOS does it, and we should probably update the JS and native code and make this change at the same time.

TODO(5279396): Make JS UI library explicitly notify the native UI module of the end of a UI transaction using a standard native call