CSP: Generate violation report data only once.
CSP: Generate violation report data only once.

Currently, we're generating violation report data twice: once when firing a
securitypolicyviolation event, and once when POSTing a violation JSON string
to a reporting endpoint.

This patch combines the two, generating data once by creating a
SecurityPolicyViolationEventInit object, and using its data both to fire the
DOM event and to populate the JSON object for reporting.

This shouldn't change any web-visible behavior; as long as the CSP tests
continue to pass, then everything's good.

Review URL: https://chromiumcodereview.appspot.com/14235005

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@148340 bbb929c8-8fbe-4397-9dbb-9b2b20218538

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