Summary: Instead of dispatching calls to the JS thread in Java, do it in the C++ bridge. This moves us closer to the cxx bridge and will allow us to dispatch to the correct web worker in C++ instead of in Java
Reviewed By: mhorowitz
Differential Revision: D2954115
fb-gh-sync-id: 7e7d4eff2c72601b8b4416f1ccd8d2985aebd755
shipit-source-id: 7e7d4eff2c72601b8b4416f1ccd8d2985aebd755