[Sync] Make BackendMigrator not wait for full sync cycles

chrome/browser/sync/engine/sync_scheduler.h

Index: chrome/browser/sync/engine/sync_scheduler.h
diff --git a/chrome/browser/sync/engine/sync_scheduler.h b/chrome/browser/sync/engine/sync_scheduler.h
index 7a025fb0478b05d9f48d6417c6334e2cbc47e39d..d71eb87d4077180061f84a0a3c2e674db2170371 100644
--- a/chrome/browser/sync/engine/sync_scheduler.h
+++ b/chrome/browser/sync/engine/sync_scheduler.h
@@ -62,14 +62,12 @@ class SyncScheduler : public sessions::SyncSession::Delegate,
   // Calls Stop().
   virtual ~SyncScheduler();
 
-  typedef Callback0::Type ModeChangeCallback;
-
   // 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.  If non-NULL,
   // |callback| will be invoked when the mode has been changed to
   // |mode|.  Takes ownership of |callback|.
-  void Start(Mode mode, ModeChangeCallback* callback);
+  void Start(Mode mode, const base::Closure& callback);
 
   // Request that any running syncer task stop as soon as possible.
   // This function can be called from any thread.  Stop must still be
@@ -82,6 +80,11 @@ class SyncScheduler : public sessions::SyncSession::Delegate,
   // Cancel all scheduled tasks.  Can be called even if already stopped.
   void Stop();
 
+  // TODO(akalin): Add callback parameters to Schedule* functions as
+  // needed.  In particular, we'd like to know when a nudge completes
+  // (or fails) so that we can acknowledge any invalidations that
+  // triggered the nudge.

[tim (not reviewing), 2011/08/26 12:41:40]

So, one of the "future todos / open questions" in the doc for SyncerThread2 was
about connecting nudges back to the originating sites. But with coalescing, that
gets pretty tricky, and I'm not convinced it's worth the complexity.  There are
some cases it would help, e.g. with ClearUserData, but for straight nudges, I
don't know.

Instead of "TODO: add Foo as needed" can you be more specific with TODOs on the
individual functions and/or file a bug?

+
   // The meat and potatoes.
   void ScheduleNudge(const base::TimeDelta& delay, NudgeSource source,
                      const syncable::ModelTypeBitSet& types,
@@ -93,7 +96,7 @@ class SyncScheduler : public sessions::SyncSession::Delegate,
   void ScheduleConfig(const syncable::ModelTypeBitSet& types,
       sync_api::ConfigureReason reason);
   void ScheduleClearUserData();
-  void ScheduleCleanupDisabledTypes();
+  void ScheduleCleanupDisabledTypes(const base::Closure& callback);

[tim (not reviewing), 2011/08/26 12:41:40]

Please comment the new parameter.

 
   // Change status of notifications in the SyncSessionContext.
   void set_notifications_enabled(bool notifications_enabled);
@@ -156,8 +159,9 @@ class SyncScheduler : public sessions::SyncSession::Delegate,
     };
     SyncSessionJob();
     SyncSessionJob(SyncSessionJobPurpose purpose, base::TimeTicks start,
-        linked_ptr<sessions::SyncSession> session, bool is_canary_job,
-        const tracked_objects::Location& nudge_location);
+                   linked_ptr<sessions::SyncSession> session,
+                   bool is_canary_job, const base::Closure& on_success,
+                   const tracked_objects::Location& nudge_location);
     ~SyncSessionJob();
     static const char* GetPurposeString(SyncSessionJobPurpose purpose);
 
@@ -165,6 +169,7 @@ class SyncScheduler : public sessions::SyncSession::Delegate,
     base::TimeTicks scheduled_start;
     linked_ptr<sessions::SyncSession> session;
     bool is_canary_job;
+    base::Closure on_success;

[tim (not reviewing), 2011/08/26 12:41:40]

I like this.  I'm still wrapping my head around what the outcome is with all the
coalescing we do, but it seems valuable in general.

 
     // This is the location the job came from.  Used for debugging.
     // In case of multiple nudges getting coalesced this stores the
@@ -251,6 +256,7 @@ class SyncScheduler : public sessions::SyncSession::Delegate,
       const base::TimeDelta& delay,
       SyncSessionJob::SyncSessionJobPurpose purpose,
       sessions::SyncSession* session,
+      const base::Closure& on_success,
       const tracked_objects::Location& from_here);
 
   // Invoke the Syncer to perform a sync.
@@ -296,7 +302,7 @@ class SyncScheduler : public sessions::SyncSession::Delegate,
 
   // 'Impl' here refers to real implementation of public functions, running on
   // |thread_|.
-  void StartImpl(Mode mode, ModeChangeCallback* callback);
+  void StartImpl(Mode mode, const base::Closure& callback);
   void ScheduleNudgeImpl(
       const base::TimeDelta& delay,
       sync_pb::GetUpdatesCallerInfo::GetUpdatesSource source,
@@ -306,7 +312,7 @@ class SyncScheduler : public sessions::SyncSession::Delegate,
       const std::vector<ModelSafeWorker*>& workers,
       const sync_pb::GetUpdatesCallerInfo::GetUpdatesSource source);
   void ScheduleClearUserDataImpl();
-  void ScheduleCleanupDisabledTypesImpl();
+  void ScheduleCleanupDisabledTypesImpl(const base::Closure& callback);
 
   // Returns true if the client is currently in exponential backoff.
   bool IsBackingOff() const;