Fix memory leak in Sync FakeServerEntity

Fix memory leak in Sync FakeServerEntity

SyncEntity protos in fake_server.cc are now populated by passing a
pointer to FakeServerEntity.SerializeAsProto. Previously,
SerializeAsProto returned a newly-created proto that was never deleted.

BUG=NONE

Committed: https://crrev.com/f89c3a34a93ae0bccf69046febe03c61b14f932f
Cr-Commit-Position: refs/heads/master@{#296733}

[pval...(no longer on Chromium), 2014-09-24 23:14:51]

pvalenzuela@chromium.org changed reviewers:
+ zea@chromium.org

[Nicolas Zea, 2014-09-24 23:16:34]

LGTM. I'm kind of surprised this didn't trigger memory leaks on the memory bots

[pval...(no longer on Chromium), 2014-09-24 23:29:07]

The CQ bit was checked by pvalenzuela@chromium.org

[commit-bot: I haz the power, 2014-09-24 23:30:59]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/600083003/1

[commit-bot: I haz the power, 2014-09-24 23:45:21]

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

[commit-bot: I haz the power, 2014-09-24 23:45:25]

Try jobs failed on following builders:
  linux_chromium_gn_rel on tryserver.chromium.linux
(http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_...)

[pval...(no longer on Chromium), 2014-09-25 17:15:37]

The CQ bit was checked by pvalenzuela@chromium.org

[commit-bot: I haz the power, 2014-09-25 17:16:24]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/600083003/1

[commit-bot: I haz the power, 2014-09-25 17:34:12]

Committed patchset #1 (id:1) as a762732abde64eb6dfd1985692c4523451b082a0

[commit-bot: I haz the power, 2014-09-25 17:34:49]

Patchset 1 (id:??) landed as
https://crrev.com/f89c3a34a93ae0bccf69046febe03c61b14f932f
Cr-Commit-Position: refs/heads/master@{#296733}