Add limit line to allow chrome to renice background tabs
Add limit line to allow chrome to renice background tabs

Change-Id: Ib9835ceb83f0309e82cb006bc2b45f85cdea69d2

BUG=9548
TEST=Login, create some tabs, click on some, examine priorities
     using top. Some should show as 25, indicating they've been
     reniced.

Review URL: http://codereview.chromium.org/5351002

joshfire/chromiumos-platform-init