Import a scoped_ptr based smart pointer into TestRunner library.

This lets us replace auto_ptr with something not deprecated on newer
STL implementations. However, unique_ptr is not present everywhere, so
we need to roll our own solution.

We also don't want to include base/memory/scoped_ptr.h directly to avoid
unnecesary cross depo dependencies.

BUG=324299
R=mkwst@chromium.org, abarth@chromium.org

Review URL: https://codereview.chromium.org/96653003

git-svn-id: svn://svn.chromium.org/blink/trunk@162908 bbb929c8-8fbe-4397-9dbb-9b2b20218538