Add missing dependency of sync_driver on policy_component.

Add missing dependency of sync_driver on policy_component.

SyncPolicyHandler depends on policy::TypeCheckingPolicyHandler which is
included in policy_component target.
GYP missed the dependency while BUILD.gn has it correctly.

BUG=

Committed: https://crrev.com/ce5511be71acd80416e51da237e6e258b1579288
Cr-Commit-Position: refs/heads/master@{#351108}

[byungchul, 2015-09-25 22:05:35]

byungchul@chromium.org changed reviewers:
+ pavely@chromium.org, stanisc@chromium.org, zea@chromium.org

[pavely, 2015-09-28 17:21:58]

lgtm

[byungchul, 2015-09-28 18:13:21]

The CQ bit was checked by byungchul@chromium.org

[commit-bot: I haz the power, 2015-09-28 18:17:17]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1371743003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1371743003/1

[commit-bot: I haz the power, 2015-09-28 19:26:14]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-09-28 19:27:07]

Patchset 1 (id:??) landed as
https://crrev.com/ce5511be71acd80416e51da237e6e258b1579288
Cr-Commit-Position: refs/heads/master@{#351108}