Add server_attachment_metadata field to EntryKernel and sync database.

sync/syncable/syncable_enum_conversions.cc

Index: sync/syncable/syncable_enum_conversions.cc
diff --git a/sync/syncable/syncable_enum_conversions.cc b/sync/syncable/syncable_enum_conversions.cc
index 0fc2147e13288e677f97c8c8ef967d9d2a33b2bb..7e0a8c984bee5fd61f946bed3a34146df9cf3413 100644
--- a/sync/syncable/syncable_enum_conversions.cc
+++ b/sync/syncable/syncable_enum_conversions.cc
@@ -163,11 +163,12 @@ const char* GetUniquePositionFieldString(UniquePositionField position_field) {
 const char* GetAttachmentMetadataFieldString(
     AttachmentMetadataField attachment_metadata_field) {
   ASSERT_ENUM_BOUNDS(ATTACHMENT_METADATA,
-                     ATTACHMENT_METADATA,
+                     SERVER_ATTACHMENT_METADATA,
                      ATTACHMENT_METADATA_FIELDS_BEGIN,
                      ATTACHMENT_METADATA_FIELDS_END - 1);
   switch(attachment_metadata_field) {
     ENUM_CASE(ATTACHMENT_METADATA);
+    ENUM_CASE(SERVER_ATTACHMENT_METADATA);
     case ATTACHMENT_METADATA_FIELDS_END: break;
   }
   NOTREACHED();