Move dom_distiller_service_factory to //chrome.

Treat the concept of "how to get the DomDistillerService to use for the given
browsing context" as an embedder-level concept rather than a concept within the
dom_distiller component.

Review URL: https://codereview.chromium.org/100623006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@238958 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 238958