Respect context death on bitmap delivery as well.

Change-Id: Ia0b2ad8cc91ce631e73296b7956ae2df7d4e4445
Add MtpConstnats from AOSP
update the gallery sample to show video support.
fix videoloader npe
Loader: minor refactor.

Add SimpleLoader to do basic no-op implementation.
Pass in resizeWidth and resizeHeight to the loadBitmap method.
FileLoader now implements loadBitmap.
IonBitmapCache performance fixes.

Remove cruft WeakReference implementation (it was disabled/broken).
Put evicted items into SoftReferenceHashtable and use that as a failover source.
Fix exif decoding bug for streams.
IonBitmapCache: clean up some target w/h code dupe.
buffer the file input stream.
Construct Ion specific Bitmap executor service.
derp
Add io executor service. Fix breakage