ninja/mac: Add iOS fields to ExtraPlistItems for ninja builds.

Add CFBundleSupportedPlatforms and UIDeviceFamily for ninja builds.
Required changing ExtraPlistItems from list of strings to json.

R=thakis@chromium.org

Review URL: https://codereview.chromium.org/27035003/



git-svn-id: http://gyp.googlecode.com/svn/trunk@1754 78cadc50-ecff-11dd-a971-7dbc132099af