Update sync API to support attachments.

sync/internal_api/public/base_node.h

Index: sync/internal_api/public/base_node.h
diff --git a/sync/internal_api/public/base_node.h b/sync/internal_api/public/base_node.h
index 425a81f944282395e6afcd92d910eadc19f6776f..93d2baf72eeddc7b4145c2d670e4c328c04acbcd 100644
--- a/sync/internal_api/public/base_node.h
+++ b/sync/internal_api/public/base_node.h
@@ -12,6 +12,7 @@
 #include "base/gtest_prod_util.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/time/time.h"
+#include "sync/api/attachments/attachment.h"
 #include "sync/base/sync_export.h"
 #include "sync/internal_api/public/base/model_type.h"
 #include "sync/protocol/sync.pb.h"
@@ -200,6 +201,9 @@ class SYNC_EXPORT BaseNode {
   // (ie. non-bookmarks).
   int GetPositionIndex() const;
 
+  // Returns this item's attachment ids.
+  const syncer::AttachmentIdList GetAttachmentIds() const;
+
   // These virtual accessors provide access to data members of derived classes.
   virtual const syncable::Entry* GetEntry() const = 0;
   virtual const BaseTransaction* GetTransaction() const = 0;