Revert of [Sync] Refactoring polling to be reliable.

sync/engine/sync_scheduler.h

 // Copyright 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 //
 // A class to schedule syncer tasks intelligently.
 #ifndef SYNC_ENGINE_SYNC_SCHEDULER_H_
 #define SYNC_ENGINE_SYNC_SCHEDULER_H_
 
 #include <string>
 
@@ skipping 50 matching lines @@
   };
 
   // All methods of SyncScheduler must be called on the same thread
   // (except for RequestEarlyExit()).
 
   SyncScheduler();
   ~SyncScheduler() override;
 
   // Start the scheduler with the given mode.  If the scheduler is
   // already started, switch to the given mode, although some
-  // scheduled tasks from the old mode may still run. |last_poll_time| will
-  // be used to decide what the poll timer should be initialized with.
-  virtual void Start(Mode mode, base::Time last_poll_time) = 0;
+  // scheduled tasks from the old mode may still run.
+  virtual void Start(Mode mode) = 0;
 
   // Schedules the configuration task specified by |params|. Returns true if
   // the configuration task executed immediately, false if it had to be
   // scheduled for a later attempt. |params.ready_task| is invoked whenever the
   // configuration task executes. |params.retry_task| is invoked once if the
   // configuration task could not execute. |params.ready_task| will still be
   // called when configuration finishes.
   // Note: must already be in CONFIGURATION mode.
   virtual void ScheduleConfiguration(const ConfigurationParams& params) = 0;
 
@@ skipping 47 matching lines @@
   // Called when credentials are updated by the user.
   virtual void OnCredentialsUpdated() = 0;
 
   // Called when the network layer detects a connection status change.
   virtual void OnConnectionStatusChange() = 0;
 };
 
 }  // namespace syncer
 
 #endif  // SYNC_ENGINE_SYNC_SCHEDULER_H_