dbus: Add TryRegisterFallback

The TryRegisterFallback works just like TryRegisterObjectPath,
with addition that the registered callbacks also apply to the specified
object path and its sub paths. This is useful to implement a "catch-all"
handler.

Currently this is needed by Bluetooth dispatcher which needs to catch
all method calls to all objects and forward them to another D-Bus
service.

Bug: 862849
Change-Id: I77b1cd924690a673c872b69a35120ee5bf223b0d
Reviewed-on: https://chromium-review.googlesource.com/1134605
Commit-Queue: Sonny Sasaka <sonnysasaka@chromium.org>
Reviewed-by: Ryo Hashimoto <hashimoto@chromium.org>
Cr-Commit-Position: refs/heads/master@{#576565}
3 files changed