Name TreeFilter and MergeFilter implementations

Naming these inner classes ensures that stack traces which contain
them will give us useful information about which filter is involved in
the trace, rather than the generated names $1, $2, etc.  This makes it
much easier to understand a stack trace at a glance.

Change-Id: Ia6a75fdb382ff6461e02054d94baf011bdeee5aa
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
2 files changed