Remove implicit conversions from scoped_refptr to T* in FileWatcher.

Since set_message_loop() takes ownership of the MessageLoop
parameter anyway, just pass it a const scoped_refptr<T>&, rather
than converting from scoped_refptr to T* back to scoped_refptr.

BUG=110610
TBR=rvargas@chromioum.org

Review URL: https://codereview.chromium.org/588003002

Cr-Commit-Position: refs/heads/master@{#295875}
2 files changed