Added --force-compositing-mode to guest mode switches. Reordered all other switches alphabetically. 
Added --force-compositing-mode to guest mode switches. Reordered all other switches alphabetically. 

BUG=chromium-os:25256
TEST=start guest session, go to about: page and make sure --force-compositing-mode shows there
Review URL: https://chromiumcodereview.appspot.com/9264024

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@118377 0039d316-1c4b-4281-b951-d872f2087c98

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