Map::CopyGeneralizeAllRepresentations() left incorrect layout descriptor in a new map.

BUG=chromium:436820
LOG=N

Review URL: https://codereview.chromium.org/759823004

Cr-Commit-Position: refs/heads/master@{#25530}
Move linked list for RPO order into BasicBlock itself.

R=titzer@chromium.org

Review URL: https://codereview.chromium.org/762723004

Cr-Commit-Position: refs/heads/master@{#25531}