After crrev.com/1584893002 base/ can use directly allocator.
The grand plan is to dismantle all the indirection layer such that:
 - base is the only thing that knows about allocator-specific details.
 - non-base code uses only base abstractions and stops looking
   at USE_TCMALLOC build flags.

This CL, specifically, addresses the profiling-related methods moving
the tcmalloc-specific dependencies to base and base only.
Other parts of the codebase will be cleaned up in separate CLs.

Also this CL removes a stale base/debug/OWNERS. That file makes
no sense these days as tracing has been moved to base/trace_event/.

BUG=564618

Review URL: https://codereview.chromium.org/1607303002

Cr-Commit-Position: refs/heads/master@{#371335}