[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 20194a1b079f5d526f9fafa50b644f97571a702c..2e9afa3bd01e64de70503029a7d58987a559f4c6 100644
--- a/sync/engine/sync_scheduler.h
+++ b/sync/engine/sync_scheduler.h
@@ -37,6 +37,28 @@ namespace browser_sync {
 
 struct ServerConnectionEvent;
 
+struct ConfigureParams {
+  ConfigureParams();
+  ConfigureParams(
+      const sync_pb::GetUpdatesCallerInfo::GetUpdatesSource& source,
+      const syncable::ModelTypeSet& types_to_config,
+      const browser_sync::ModelSafeRoutingInfo& routing_info,
+      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 GetKey command.
+  bool need_encryption_key;
+  // Callback to invoke on configuration completion.
+  base::Closure ready_task;
+};
+
 class SyncScheduler : public sessions::SyncSession::Delegate {
  public:
   enum Mode {
@@ -63,10 +85,15 @@ 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|. Returns true if
+  // the configuration task completes, false if a retry had to be scheduled
+  // for later completion. |params.ready_task| is invoked whenever the
+  // configuration task completes.
+  // 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,
@@ -85,12 +112,6 @@ 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 Configure(
-      syncable::ModelTypeSet types,
-      sync_pb::GetUpdatesCallerInfo::GetUpdatesSource source);
-
   void ClearUserData();
 
   void CleanupDisabledTypes();
@@ -160,6 +181,7 @@ class SyncScheduler : public sessions::SyncSession::Delegate {
     SyncSessionJob();
     SyncSessionJob(SyncSessionJobPurpose purpose, base::TimeTicks start,
         linked_ptr<sessions::SyncSession> session, bool is_canary_job,
+        ConfigureParams config_params,
         const tracked_objects::Location& nudge_location);
     ~SyncSessionJob();
     static const char* GetPurposeString(SyncSessionJobPurpose purpose);
@@ -168,6 +190,7 @@ 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