buffet: Add DBusCommandDispacher and hook it up to CommandQueue

Added DBusCommandDispacher class that maintains DBusCommandProxy object
for each instance of CommandInstance class added to the CommandQueue.

As soon as a command instance is removed from the queue, D-Bus command
dispatcher removes the corresponding command proxy object from D-Bus.

BUG=chromium:374864
TEST=FEATURES=test emerge-link buffet

Change-Id: Ib7ce7370bd3ee471e22f02b8546675021ff063d7
Reviewed-on: https://chromium-review.googlesource.com/211642
Tested-by: Alex Vakulenko <avakulenko@chromium.org>
Reviewed-by: Christopher Wiley <wiley@chromium.org>
Commit-Queue: Alex Vakulenko <avakulenko@chromium.org>
7 files changed
tree: 415b1ffa655e6a1f2095966d0f9b9da837e052f8
  1. buffet/