[Sync] Refactor sync configuration logic.

sync/engine/sync_scheduler.h

Index: sync/engine/sync_scheduler.h
diff --git a/sync/engine/sync_scheduler.h b/sync/engine/sync_scheduler.h
index dfd63e4a0b4306f79cf10154156e689f73c8a9b8..3019e0fc8eb45f46bfe2fb43b840890bd610411c 100644
--- a/sync/engine/sync_scheduler.h
+++ b/sync/engine/sync_scheduler.h
@@ -50,6 +50,31 @@ class SyncScheduler : public sessions::SyncSession::Delegate {
     NORMAL_MODE,
   };
 
+  struct ConfigureParams {
+    ConfigureParams();
+    ConfigureParams(
+        const sync_pb::GetUpdatesCallerInfo::GetUpdatesSource& source,
+        const syncable::ModelTypeSet& types_to_config,
+        const browser_sync::ModelSafeRoutingInfo& routing_info,
+        bool need_cleanup,
+        bool need_encryption_key,
+        const base::Closure& ready_task);
+    ~ConfigureParams();
+
+    // Source for the configuration.
+    sync_pb::GetUpdatesCallerInfo::GetUpdatesSource source;
+    // The types that should be downloaded.
+    syncable::ModelTypeSet types_to_config;
+    // The new routing info (superset of types to be downloaded).
+    ModelSafeRoutingInfo routing_info;
+    // Whether we need to perform a CleanupDisabledTypes command.
+    bool need_cleanup;
+    // Whether we need to perform a GetKey command.
+    bool need_encryption_key;
+    // Callback to invoke on configuration completion.
+    base::Closure ready_task;
+  };
+
   // All methods of SyncScheduler must be called on the same thread
   // (except for RequestEarlyExit()).
 
@@ -63,10 +88,12 @@ class SyncScheduler : public sessions::SyncSession::Delegate {
 
   // 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, const base::Closure& callback);
+  // scheduled tasks from the old mode may still run.
+  void Start(Mode mode);
+
+  // Performs the configuration tasks specified by |params|.
+  // Note: must already be in CONFIGURATION mode.
+  bool Configure(const ConfigureParams& params);
 
   // Request that any running syncer task stop as soon as possible and
   // cancel all scheduled tasks. This function can be called from any thread,
@@ -85,18 +112,8 @@ class SyncScheduler : public sessions::SyncSession::Delegate {
       const syncable::ModelTypePayloadMap& types_with_payloads,
       const tracked_objects::Location& nudge_location);
 
-  // Note: The source argument of this function must come from the subset of
-  // GetUpdatesCallerInfo values related to configurations.
-  void ScheduleConfig(
-      syncable::ModelTypeSet types,
-      sync_pb::GetUpdatesCallerInfo::GetUpdatesSource source);
 
   void ScheduleClearUserData();
-  // If this is called before Start(), the cleanup is guaranteed to
-  // happen before the Start finishes.
-  //
-  // TODO(akalin): Figure out how to test this.
-  void ScheduleCleanupDisabledTypes();
 
   // Change status of notifications in the SyncSessionContext.
   void set_notifications_enabled(bool notifications_enabled);
@@ -171,6 +188,7 @@ class SyncScheduler : public sessions::SyncSession::Delegate {
     base::TimeTicks scheduled_start;
     linked_ptr<sessions::SyncSession> session;
     bool is_canary_job;
+    ConfigureParams config_params;
 
     // This is the location the job came from.  Used for debugging.
     // In case of multiple nudges getting coalesced this stores the
@@ -310,7 +328,7 @@ class SyncScheduler : public sessions::SyncSession::Delegate {
 
   // 'Impl' here refers to real implementation of public functions, running on
   // |thread_|.
-  void StartImpl(Mode mode, const base::Closure& callback);
+  void StartImpl(Mode mode);
   void StopImpl(const base::Closure& callback);
   void ScheduleNudgeImpl(
       const base::TimeDelta& delay,