Disable TCP Keep Alive on mobile to reduce power usage.

TCP Keep Alives will periodically send TCP packets to keep the
connection alive. This may wake up the radio, which is expensive in
terms of power utilization. Disable it on mobile.

BUG=258361

Review URL: https://codereview.chromium.org/106003004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@243047 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 243047