[Sync] Add ClearServerData support to Sync Scheduler

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 28 matching lines @@
   // The types that should be downloaded.
   ModelTypeSet types_to_download;
   // The new routing info (superset of types to be downloaded).
   ModelSafeRoutingInfo routing_info;
   // Callback to invoke on configuration completion.
   base::Closure ready_task;
   // Callback to invoke on configuration failure.
   base::Closure retry_task;
 };
 
+struct SYNC_EXPORT_PRIVATE ClearParams {
+  ClearParams(const base::Closure& report_success_task);
+  ~ClearParams();
+
+  // Callback to invoke on successful completion.
+  base::Closure report_success_task;
+};
+
 class SYNC_EXPORT_PRIVATE SyncScheduler
     : public sessions::SyncSession::Delegate {
  public:
   enum Mode {
     // In this mode, the thread only performs configuration tasks.  This is
     // designed to make the case where we want to download updates for a
     // specific type only, and not continue syncing until we are moved into
     // normal mode.
     CONFIGURATION_MODE,
+    // This mode is used to issue a clear server data command.  The scheduler
+    // may only transition to this mode from the CONFIGURATION_MODE.  When in
+    // this mode, the only schedulable operation is |SchedulerClearServerData|.
+    CLEAR_SERVER_DATA_MODE,
     // Resumes polling and allows nudges, drops configuration tasks.  Runs
     // through entire sync cycle.
     NORMAL_MODE,
   };
 
   // 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;
 
   // 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;
 
+  // Schedules clear of server data in preparation for transitioning to
+  // passphrase encryption. The scheduler must be in CLEAR_SERVER_DATA_MODE
+  // before calling this method.
+  virtual void ScheduleClearServerData(const ClearParams& params) = 0;
+
   // Request that the syncer avoid starting any new tasks and prepare for
   // shutdown.
   virtual void Stop() = 0;
 
   // The meat and potatoes. All three of the following methods will post a
   // delayed task to attempt the actual nudge (see ScheduleNudgeImpl).
   //
   // NOTE: |desired_delay| is best-effort. If a nudge is already scheduled to
   // depart earlier than Now() + delay, the scheduler can and will prefer to
   // batch the two so that only one nudge is sent (at the earlier time). Also,
@@ skipping 37 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_