Bug 867755 - Support OnDataAvailable and OnStopRequest off main thread for image loading r=seth
Bug 867755 - Make DiscardTracker thread-safe r=seth
Bug 867755 - Dispatch imgRequestProxy notifications r=seth
Bug 867755 - Detect if DiscardTracker has shutdown r=seth
Bug 867755 - Return already_AddRefed from GetStatusTracker instead of C++ ref r=seth
Bug 867755 - Add strong refcnting for derived classes of mozilla::image::Image r=seth