base

Share chunks between all ByteArrayBuilders.

If a single ByteArrayBuilder accumulates many chunks, it is possible that many
of those chunks will not be reused and will just take up memory in the pool. If
the pool is shared across all instances, fewer chunks need to be allocated. This
allows a site like http://www.606studios.com/bendisboard/showthread.php?t=170286
to load without crashing due to OOM.

The shared pool contains SoftReferences to each chunk. If the vm feels memory
pressure, it is allowed to mark these references for collection. Before
accessing the pool of chunks, I remove any queued references from the pool.

Cleanup ByteArrayBuilder a little by removing unused methods and fields.
Document some synchronization spots in LoadListener and add a lock when
downloading a certificate.

Bug: 1637965