Collect stats on MIME types seen for Flash plug-in loads. This will help us

      to make a decision about whether we can tighten anything up for sites which
don't use X-Content-Type-Options: nosniff.
Also make the MIME type match a substring match just in case there are any:
application/x-shockwave-flash; charset=binary


BUG=75070
Review URL: http://codereview.chromium.org/7397001

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@92760 0039d316-1c4b-4281-b951-d872f2087c98