am 7ab900ed: Merge change Ic8093c11 into eclair

Merge commit '7ab900edd69324e5eeb2c6b01ef3ef5e836689a3' into eclair-mr2

* commit '7ab900edd69324e5eeb2c6b01ef3ef5e836689a3':
  Hold a lock while we access the preview heap.