Note that AnimationSurfaceProvider will override these methods to give a
proper implementation in a later patch in this series. For now, they are
mostly stubbed, using the default implementation from ISurfaceProvider.
They focus on the main operations we perform on an animation:
1) Progressing through the animation, e.g. advancing a frame. If we
don't decode the whole animation up front, we need to know at the
decoder level where we are in the display of the animation.
2) Restarting an animation from the beginning. This is a specialized
case of the above, where we want to skip explicitly advancing through
the remaining frames and instead restart at the beginning. The decoder
may have already discarded the earliest frames and must start redecoding
them.
3) Knowing whether or not the decoder is still active, e.g. can we be
missing frames.
The shared memory handle reporting has been generalized to be an
external handle reporting. This is used for both shared memory, and for
volatile memory (on Android.) This will allow us to have a better sense
of just how many handles are being used by images on Android.
Additionally we were not properly reporting forced heap allocated
memory, if we were putting animated frames on the heap. This is because
we used SourceSurfaceAlignedRawData without implementing
AddSizeOfExcludingThis.
Andrew Osmond
Kartikaya Gupta
Seth Fowler