[Sync] Move sessions/ to engine/cycle/ and rename things to match.

components/sync/core_impl/sync_manager_impl.h

Index: components/sync/core_impl/sync_manager_impl.h
diff --git a/components/sync/core_impl/sync_manager_impl.h b/components/sync/core_impl/sync_manager_impl.h
index 0d7d7d34a0544ced427099700fa2620ced1f4a39..3483d9b95bb28d6acc97283942e0129dd39b5f73 100644
--- a/components/sync/core_impl/sync_manager_impl.h
+++ b/components/sync/core_impl/sync_manager_impl.h
@@ -38,14 +38,11 @@ namespace syncer {
 
 class ModelTypeRegistry;
 class SyncAPIServerConnectionManager;
+class SyncCycleContext;
 class TypeDebugInfoObserver;
 class WriteNode;
 class WriteTransaction;
 
-namespace sessions {
-class SyncSessionContext;
-}
-
 // SyncManager encapsulates syncable::Directory and serves as the parent of all
 // other objects in the sync API.  If multiple threads interact with the same
 // local sync repository (i.e. the same sqlite database), they should share a
@@ -289,8 +286,8 @@ class SyncManagerImpl
   std::unique_ptr<ModelTypeRegistry> model_type_registry_;
 
   // A container of various bits of information used by the SyncScheduler to
-  // create SyncSessions.  Must outlive the SyncScheduler.
-  std::unique_ptr<sessions::SyncSessionContext> session_context_;
+  // create SyncCycles.  Must outlive the SyncScheduler.
+  std::unique_ptr<SyncCycleContext> cycle_context_;
 
   // The scheduler that runs the Syncer. Needs to be explicitly
   // Start()ed.