Delete callback for CallMethod always on the origin thread.

The callback may have bound arguments, which could be thread unsafe.
So, the callback needs to be destroyed on the origin thread
always.
If PostTask from D-Bus thread to the origin thread fails,
let the callback leak intentionally.

BUG=778329
TEST=Build. Ran trybot.

Change-Id: Ib9c1d82e71f5f199a2cea087f8265326fc1f3da2
Reviewed-on: https://chromium-review.googlesource.com/772034
Reviewed-by: Ryo Hashimoto <hashimoto@chromium.org>
Commit-Queue: Hidehiko Abe <hidehiko@chromium.org>
Cr-Commit-Position: refs/heads/master@{#518145}

CrOS-Libchrome-Original-Commit: 7f05f78dd4bf63066dfd2c9c5a99b4c2fb20e268
3 files changed
tree: d1e596f98d0a2053aea1334da20f44f98f037f7a
  1. base/
  2. build/
  3. components/
  4. dbus/
  5. device/
  6. ipc/
  7. mojo/
  8. testing/
  9. third_party/
  10. ui/