Stop supporting invalid CSP directives in meta tags

third_party/WebKit/LayoutTests/http/tests/navigation/pushstate-at-unique-origin-denied.html

-<meta http-equiv="Content-Security-Policy" content="sandbox allow-scripts">
-<script src="../resources/testharness.js"></script>
-<script src="../resources/testharnessreport.js"></script>
-<script>
-test(function () {
-    assert_throws('SecurityError', function () {
-        history.pushState(null, null, document.URL + "/path");
-    });
-}, 'pushState to a new path in unique origin should fail with SecurityError');
-test(function () {
-    try {
-        history.pushState(null, null, document.URL + "#hash");
-        done();
-    } catch (e) {
-        assert_unreached("pushState to a new hash should not fail.");
-    }
-}, 'pushState to new hash in unique origin should not fail with SecurityError');
-</script>