floss: libhrome r939949 uprev

For CrOS floss.
* migrate base::TimeDelta::From* to base:* for libchrome r931007+
  The functions were migrated on upstream in r927512
  (crrev.com/c/3198824) and removed in r931007 (crrev.com/c/3219846).
  Change recreated by running sed.
* task-related files are moved from base/ to base/task/ in r930627
  (crrev.com/c/3216953).
Use BASE_VER guard for aosp which is using an older libchrome.

Bug: 211560276
Tag: #floss
Test: FEATURES=test emerge-hatch floss
Change-Id: I88799df149f38e8ad7ed9ac574f8a578326784cc