Highlight in chains

This will prevent Elasticsearch from trying to highlight fields that we're
not going to use because a field "before" it was highlighted.

Doesn't do anything unless you have I0326baaf497a305348eb536461cd8d6404795d2c
deployed to the Elasticsearch cluster.

Change-Id: Ib2d9713e9b9feae04f332cc8ca618e063e9a64c4
Merge "Highlight in chains"