buffet: Add property update signals to ExportedPropertSet

BUG=chromium:356368
TEST=unit tests pass, added more

Change-Id: I4c4beabce9bf6d3daf444066b2ce26cf13d50d10
Reviewed-on: https://chromium-review.googlesource.com/192725
Tested-by: Christopher Wiley <wiley@chromium.org>
Reviewed-by: Alex Vakulenko <avakulenko@chromium.org>
Commit-Queue: Christopher Wiley <wiley@chromium.org>
3 files changed
tree: 30bd706be784cb426d7f9fccd66f1b056b5a5fa3
  1. buffet/