Added a policy writer for iOS Plists.

BUG=360508
R=pastarmovj@chromium.org

Review URL: https://codereview.chromium.org/227073006

git-svn-id: http://grit-i18n.googlecode.com/svn/trunk@159 7262f16d-afe8-6277-6482-052fa10e57b1
Added files missing from revision 159.

BUG=360508
TBR=pastarmovj@chromium.org

Review URL: https://codereview.chromium.org/227493005

git-svn-id: http://grit-i18n.googlecode.com/svn/trunk@160 7262f16d-afe8-6277-6482-052fa10e57b1