[Sync] Componentize synced_tab_delegate

components/sync_driver/sync_client.h

Index: components/sync_driver/sync_client.h
diff --git a/components/sync_driver/sync_client.h b/components/sync_driver/sync_client.h
index 5039456d005a61ce66efea73782b7029caeffc49..7bc10f3b033368dd184cb1f85153a3710594ad2e 100644
--- a/components/sync_driver/sync_client.h
+++ b/components/sync_driver/sync_client.h
@@ -42,6 +42,10 @@ namespace syncer {
 class SyncableService;
 }  // namespace syncer
 
+namespace sync_sessions {
+class SyncSessionsClient;
+}  // namespace sync_sessions
+
 namespace sync_driver {
 
 class SyncApiComponentFactory;
@@ -84,6 +88,7 @@ class SyncClient {
   GetWebDataService() = 0;
   virtual BookmarkUndoService* GetBookmarkUndoServiceIfExists() = 0;
   virtual scoped_refptr<syncer::ExtensionsActivity> GetExtensionsActivity() = 0;
+  virtual sync_sessions::SyncSessionsClient* GetSyncSessionsClient() = 0;
 
   // Returns a weak pointer to the syncable service specified by |type|.
   // Weak pointer may be unset if service is already destroyed.