Add base/memory/ptr_util.h for https://codereview.chromium.org/1911823002/

Change-Id: I6314d2eb5e715d20a129e75d417d52e35e60edf2
Reviewed-on: https://chromium-review.googlesource.com/340458
Reviewed-by: Robert Sesek <rsesek@chromium.org>
1 file changed