Revert of Disabled flaky sync test

Revert of Disabled flaky sync test (patchset #1 id:1 of https://codereview.chromium.org/2963933002/ )

Reason for revert:

Findit (https://goo.gl/kROfz5) identified CL at revision 483304 as the
culprit for failures in the build cycles as shown on:
https://findit-for-me.appspot.com/waterfall/culprit?key=ag9zfmZpbmRpdC1mb3ItbWVyRAsSDVdmU3VzcGVjdGVkQ0wiMWNocm9taXVtL2FmMWYyMDY5MGJlZDQ4ZWM5YTU2NzAwYTUyY2Q1YjY5NjJmZjcxOGEM

Original issue's description:
> Disabled flaky sync test
> 
> NOTRY=true
> TBR=yfriedman@chromium.org
> BUG=737862
> 
> Review-Url: https://codereview.chromium.org/2963933002
> Cr-Commit-Position: refs/heads/master@{#483304}
> Committed: https://chromium.googlesource.com/chromium/src/+/af1f20690bed48ec9a56700a52cd5b6962ff718a

TBR=yfriedman@chromium.org,benwells@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=737862

[findit-for-me, 2017-06-29 06:13:11]

Created Revert of Disabled flaky sync test

[findit-for-me, 2017-06-29 06:13:12]

findit-for-me@appspot.gserviceaccount.com changed reviewers:
+ benwells@google.com, engedy@google.com, msw@google.com, rouslan@google.com

[findit-for-me, 2017-06-29 06:13:13]

Sheriffs, CL owner or CL reviewers:

Please confirm and "Quick L-G-T-M & CQ" this revert if it is correct.
If it is a false positive, please close it.

Findit (https://goo.gl/kROfz5) identified the original CL as the culprit
for failures in the build cycles as shown on:
https://findit-for-me.appspot.com/waterfall/culprit?key=ag9zfmZpbmRpdC1mb3Itb...