Stop deleting ObjectProxy::OnPendingCallIsCompleteData manually

Stop deleting ObjectProxy::OnPendingCallIsCompleteData manually

Instead, let libdbus handle it.
This also makes it easier to implement method call cancellation.

BUG=471175
Committed: https://crrev.com/9aa653d4ac52f2c89bfa5164a5eddd8164bb9987
Cr-Commit-Position: refs/heads/master@{#322746}

[hashimoto, 2015-03-26 04:58:58]

hashimoto@chromium.org changed reviewers:
+ satorux@chromium.org

[satorux1, 2015-03-30 06:11:29]

good catch! LGTM

[hashimoto, 2015-03-30 06:12:12]

The CQ bit was checked by hashimoto@chromium.org

[commit-bot: I haz the power, 2015-03-30 06:12:24]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1032263002/1

[commit-bot: I haz the power, 2015-03-30 06:52:27]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-03-30 06:53:23]

Patchset 1 (id:??) landed as
https://crrev.com/9aa653d4ac52f2c89bfa5164a5eddd8164bb9987
Cr-Commit-Position: refs/heads/master@{#322746}