increase default protocol version from 42 to 43

[Sync] Server side update the protocol version, because server side adding a error type, which is partial_faulure. we already support this error type, so this change just need to update default version.

BUG=470736
Committed: https://crrev.com/5d75fb5a411a0f9cb18d893965c8e207f08a3918
Cr-Commit-Position: refs/heads/master@{#322329}

[Gang Wu, 2015-03-26 00:29:20]

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

[Gang Wu, 2015-03-26 00:29:33]

please take a look

[Nicolas Zea, 2015-03-26 01:31:21]

Could you update the commit message to start with [Sync]? This helps us identify
sync commits easily.

Also, it would be good to have a message explaining why we're updating from 42
to 43 (I believe it has to do with partial getupdate/commit failures)

LGTM otherwise.

[Gang Wu, 2015-03-26 05:48:13]

The CQ bit was checked by gangwu@chromium.org

[commit-bot: I haz the power, 2015-03-26 05:48:29]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1030293002/1

[commit-bot: I haz the power, 2015-03-26 05:52:18]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-03-26 05:53:13]

Patchset 1 (id:??) landed as
https://crrev.com/5d75fb5a411a0f9cb18d893965c8e207f08a3918
Cr-Commit-Position: refs/heads/master@{#322329}