Make NetworkList and NetworkMonitor APIs public

BUG=281781
R=nfullagar@chromium.org, thakis@chromium.org, yzshen@chromium.org
TBR=cevans@chromium.org

Review URL: https://codereview.chromium.org/23450012

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@224626 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 224626