GUI testing is important for examining the end-to-end workflows and usability of GUI-based software. To reduce the manual effort of writing GUI tests, recent research has explored the potential of automatically reusing GUI tests by transferring them across similar applications. However, what is missing from the prior work is that such transfer may be required for apps available on different platforms. In particular, both web and Android are dominant platforms on which many organizations provide their software services. At the state-of-the-practice, even if the web and Android versions of an app provisioned by an organization substantially share the functionality, the developers have to manually write separate sets of tests for each version. This paper proposes TransDroid, an automated tool that transfers GUI tests from a web app to its Android counterpart. Evaluation of TransDroid on real-world web and Android apps corroborates its effectiveness by achieving 77% success rate among the attempted transfers, along with 82% precision and 99% recall in the mapping of the GUI events and oracles.