Replace AllowCrossThreadAccess() + non-GCed pointers with crossThreadUnretained())

This CL adds CrossThreadCopier for crossThreadUnretained() in CrossThreadCopier.h.
Other changes are made by:
  sed -i 's/AllowCrossThreadAccess/crossThreadUnretained/g'

BUG=597856
CQ_INCLUDE_TRYBOTS=tryserver.chromium.win:win_optional_gpu_tests_rel;tryserver.chromium.mac:mac_optional_gpu_tests_rel

Review-Url: https://codereview.chromium.org/1925583003
Cr-Commit-Position: refs/heads/master@{#401578}
31 files changed