[sync] Componentize sync: Part 6: Add more SYNC_EXPORTs to files in src/sync/

sync/internal_api/public/sync_manager.h

Index: sync/internal_api/public/sync_manager.h
diff --git a/sync/internal_api/public/sync_manager.h b/sync/internal_api/public/sync_manager.h
index 97469285fa78d028000c2e7e3ba28f097b4a3154..9ae1940f18eca46c3d5921bd71580f4e9d70ba9a 100644
--- a/sync/internal_api/public/sync_manager.h
+++ b/sync/internal_api/public/sync_manager.h
@@ -131,7 +131,7 @@ class SYNC_EXPORT SyncManager {
   // Like ChangeDelegate, except called only on the sync thread and
   // not while a transaction is held.  For objects that want to know
   // when changes happen, but don't need to process them.
-  class ChangeObserver {
+  class SYNC_EXPORT_PRIVATE ChangeObserver {
    public:
     // Ids referred to in |changes| may or may not be in the write
     // transaction specified by |write_transaction_id|.  If they're