Dynamic point lights generate shader compile errors on HTML5

The new ES2 movable point lights look promising. Unfortunately, there seems to be an issue with them in HTML5 builds. They work great in the ES2 preview mode in the editor, but when running in an actual browser they cause many shaders to fail to compile, which results in the scene looking completely black, or blank, or strangely corrupted. I've created a simple project that reproduces the issue in an HTML5 build on UE4.9 Preview 3:

https://github.com/Quadtree/UE4HTML5PointLightIssue

Simply launch into HTML5 and you should see some geometry missing, with shader compiler errors in the log.