Add AttachmentMetadata to Sync's EntryKernel.

sync/syncable/entry.cc

Index: sync/syncable/entry.cc
diff --git a/sync/syncable/entry.cc b/sync/syncable/entry.cc
index 852c33e32edee914422dfbf8c4d1d6c5e138df13..2be2aad687fdf56dee9baf125420868446780be7 100644
--- a/sync/syncable/entry.cc
+++ b/sync/syncable/entry.cc
@@ -157,6 +157,13 @@ std::ostream& operator<<(std::ostream& os, const Entry& entry) {
        << kernel->ref(static_cast<UniquePositionField>(i)).ToDebugString()
        << ", ";
   }
+  for ( ; i < ATTACHMENT_METADATA_FIELDS_END; ++i) {
+    std::string escaped_str = base::EscapeBytesAsInvalidJSONString(
+        kernel->ref(static_cast<AttachmentMetadataField>(i))
+            .SerializeAsString(),
+        false);
+    os << g_metas_columns[i].name << ": " << escaped_str << ", ";
+  }
   os << "TempFlags: ";
   for ( ; i < BIT_TEMPS_END; ++i) {
     if (kernel->ref(static_cast<BitTemp>(i)))