More tests added to cctest/tests/test-migrations.cc.
More tests added to cctest/tests/test-migrations.cc.

This also includes a regression test for crbug/459512.

BUG=chromium:459512
LOG=N

Review URL: https://codereview.chromium.org/947103002

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#26795}

UniversalFuture/moosh,UniversalFuture/moosh,UniversalFuture/moosh,UniversalFuture/moosh