Remove some unused #define in Platform.h
Remove some unused #define in Platform.h

HAVE_COMPOSITOR_FILTER_OUTSETS was a left over from a rollout.
The other ones must have been used by other platforms and are
no longer required.

Review URL: https://chromiumcodereview.appspot.com/14786003

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@149553 bbb929c8-8fbe-4397-9dbb-9b2b20218538

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