Disable background linting using WebWorkers

Ace uses JavaScript Web Workers for linting code. Ace's attempt to load workers
in JS and JSON modes runs into the mismatch between its require()
implementation and ResourceLoader, resulting in a request for
/worker_<lang>.js, which 404s.

Change-Id: Ia60ef2122c015635ef0ad963a956b4f77cd6f7e8
Merge "Disable background linting using WebWorkers"