Move scoped_refptr to its own file

Blink will start using scoped_refptr, but will not use base::RefCounted
directly ATM. This CL moves scoped_refptr to its own file, so that
Blink can check ref_counted.h inclusion by DEPS rule. And avoid using
base::RefCounted accidentally.

Bug: 763844
Change-Id: I6f7f076b4f5c0a5ab4b49ef72310cf37faac3bf5
Reviewed-on: https://chromium-review.googlesource.com/711818
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Commit-Queue: Taiju Tsuiki <tzik@chromium.org>
Cr-Commit-Position: refs/heads/master@{#508579}
3 files changed