[GRC] Process Coordination Unit support for Global Resource Controller

Quick design tl;dr:

* ProcessCoordinationUnitImpl
  Specific implementation of CoordinationUnitImpl for tracking
  processes within GRC of which it is derived from

* CoordinationUnitFactory
  Currently supports making ProcessCoordinationUnitImpl for
  CoordinationUnitType:kProcess and then a vanilla
  CoordinationUnitImpl for any ohter CoordinationUnitType

* CoordinationUnitImplBaseTest
  A base class for unit testing CoordinationUnitImpl and
  its derived classes

R=oysteine@chromium.org, rockot@chromium.org
BUG=724306

Review-Url: https://codereview.chromium.org/2892443002
Cr-Commit-Position: refs/heads/master@{#473620}
18 files changed