Change file watching back to polling.#8196

Merged

zhengbli merged 2 commits intomicrosoft:masterfrom zhengbli:fileWatcherBackToPolling

Apr 25, 2016

+130-113

Commits on Apr 19, 2016

So we are back to polling.
zhengbli
committed

Commits on Apr 22, 2016

Add env to allow switch to non-polling if really wants to
zhengbli
committed