Remove obsolete and unused WebPreferences header.
Remove obsolete and unused WebPreferences header.

R=jorlow
BUG=none
TEST=none

Review URL: http://codereview.chromium.org/165305

git-svn-id: http://src.chromium.org/svn/trunk/src@23047 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: c7940de4913cbd07fff755c82884ffcde3670ce8
meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser