sync: Remove unused private fields

sync: Remove unused private fields

To avoid having a lot of -Wunused-private-field warnings when using "=delete" to implement DISALLOW_COPY_AND_ASSIGN.

BUG=447445
Committed: https://crrev.com/07b9104f3a7abdf9e5646fe8af8feb4f99afe665
Cr-Commit-Position: refs/heads/master@{#310766}

[hashimoto, 2015-01-09 10:16:00]

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

[Andrew T Wilson (Slow), 2015-01-09 11:11:09]

lgtm

[hashimoto, 2015-01-09 13:09:19]

The CQ bit was checked by hashimoto@chromium.org

[commit-bot: I haz the power, 2015-01-09 13:10:33]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/824893004/1

[commit-bot: I haz the power, 2015-01-09 13:53:55]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-01-09 13:54:50]

Patchset 1 (id:??) landed as
https://crrev.com/07b9104f3a7abdf9e5646fe8af8feb4f99afe665
Cr-Commit-Position: refs/heads/master@{#310766}