Bug 844323 - Part 3: ProcessPriorityManager tests.
Bug 847592 - Part 1: Add an additional lowCPUPriority argument to hal::SetProcessPriority.
Bug 847592 - Part 2: When a process has priority FOREGROUND_HIGH, renice all other processes.
Bug 847592 - Tests for renicing all other processes when one process gets priority FOREGROUND_HIGH