Sync Request Messages Must Be Deduped

[wixbot]

Background thread's main message loop must make an attempt to de-dupe BACKGROUND_THREAD_SYNC_FROM_MONITOR requests coming in. Otherwise we can sometimes do more work than needed, and in some extreme cases (such as an app that often modifies its files and yet keeps them in use when we want to sync them such as SpaceChem) can cause such a flood of retrying sync requests that it blows up the thread's message queue.

Originally opened by mike-gc

[wixbot]

Originally changed by mike-gc
Resolution set to Fixed
Status changed from Open to Resolved