Mark syncer::InvalidationVersionLessThan with SYNC_EXPORT.

BUG=361616
R=tim@chromium.org

Review URL: https://codereview.chromium.org/231203002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@263126 0039d316-1c4b-4281-b951-d872f2087c98

sync/notifier/invalidation_util.h

@@ -40,7 +40,7 @@ struct SYNC_EXPORT ObjectIdLessThan {
                   const invalidation::ObjectId& rhs) const;
 };
 
-struct InvalidationVersionLessThan {
+struct SYNC_EXPORT InvalidationVersionLessThan {
   bool operator()(const syncer::Invalidation& a,
                   const syncer::Invalidation& b) const;
 };