libchrome: add support for synchronous PropertySet::Set to dbus

libchrome: add support for synchronous PropertySet::Set to dbus

The existing PropertySet::Set function is asynchronous.
This CL adds the synchronous version of PropertySet::Set.
It is defined as PropertySet::SetAndBlock.

BUG=https://b.corp.google.com/u/0/issues/24131409
TEST=manually tested

Committed: https://crrev.com/8dbb26ec72f34075d951cbfd576fe2165e2f2e69
Cr-Commit-Position: refs/heads/master@{#350268}

[nywang, 2015-09-21 21:26:56]

nywang@chromium.org changed reviewers:
+ pstew@chromium.org, satorux@chromium.org, zqiu@chromium.org

[nywang, 2015-09-22 21:19:26]

nywang@chromium.org changed reviewers:
+ keybuk@chromium.org

[keybuk, 2015-09-22 22:41:18]

lgtm

[nywang, 2015-09-22 22:41:58]

The CQ bit was checked by nywang@chromium.org

[commit-bot: I haz the power, 2015-09-22 22:42:31]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1361503003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1361503003/1

[commit-bot: I haz the power, 2015-09-22 23:25:46]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-09-22 23:25:47]

Try jobs failed on following builders:
  chromeos_amd64-generic_chromium_compile_only_ng on tryserver.chromium.linux
(JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/chromeos_amd64-...)

[nywang, 2015-09-22 23:35:11]

The CQ bit was checked by nywang@chromium.org

[commit-bot: I haz the power, 2015-09-22 23:36:49]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1361503003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1361503003/1

[commit-bot: I haz the power, 2015-09-23 00:06:47]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-09-23 00:08:58]

Patchset 1 (id:??) landed as
https://crrev.com/8dbb26ec72f34075d951cbfd576fe2165e2f2e69
Cr-Commit-Position: refs/heads/master@{#350268}