facebook/presto — pull request #1707 by electrum (2014-09-23 20:33:37+00:00)
Title: Always clear thread context class loader for plugins

The default context class loader for the main thread is the application
class loader, which is never correct for plugins. Ideally, plugins should
be loading code relative to their own classes rather than relying on the
context class loader, but many libraries prefer the context class loader.