Revert of [Sync] Refactoring polling to be reliable. (patchset #5 id:80001 of https://codereview.chromium.org/1132013004/)

Reason for revert:
Failing on valgrind bots

Original issue's description:
> [Sync] Refactoring polling to be reliable.
>
> Polling is now an important component of sync health, as it can sometimes be
> the only time we'll query for certain datatypes. As such, the following
> has changed:
> - Polls that fail will be retried (with backoff).
> - As such, the logic to force a poll after an auth error isn't needed anymore
> - The last successful poll time will be persisted in the sync prefs.
> - On startup, schedule the first poll for last_poll_time + poll_interval
>   (or Now(), whichever is latest).
> - Receiving a new poll interval from the server will update the poll timer
> - The poll timer is now a one shot timer, and only restarts on success
> - Some code cleanup to make the above more straightforward
>
> BUG=482154
>
> Committed: https://crrev.com/3777d8727d7b4caedfb72bfdcbe2fea1f1d1d594
> Cr-Commit-Position: refs/heads/master@{#329669}

TBR=pavely@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=482154

Review URL: https://codereview.chromium.org/1144443004

Cr-Commit-Position: refs/heads/master@{#329683}

1 files changed, 0 insertions, 3 deletions

diff --git a/components/sync_driver/pref_names.cc b/components/sync_driver/pref_names.cc
index 1a5727a..b167a0b 100644
--- a/components/sync_driver/pref_names.cc
+++ b/components/sync_driver/pref_names.cc
@@ -11,9 +11,6 @@ namespace prefs {
 // 64-bit integer serialization of the base::Time when the last sync occurred.
 const char kSyncLastSyncedTime[] = "sync.last_synced_time";
 
-// 64-bit integer serialization of the base::Time of the last sync poll.
-const char kSyncLastPollTime[] = "sync.last_poll_time";
-
 // Boolean specifying whether the user finished setting up sync.
 const char kSyncHasSetupCompleted[] = "sync.has_setup_completed";