fix undefined function check_starting_element

A typo I guess, but now the test runs again.
first checkin of tests and supporting files
Added positive test, updated checkReport to handle JSON-formatted HTTP errors from wptserve
Fixed headers with incorrect cookie names, undeleted addInlineTests...
better error handling for empty stash
fixed typo wihtout->without
add distinct tests for eval blocking and reporting
clarify reporting test description
use assert_unreached for tests which should not run according to policy
start async tests and use step(assert_unreachable) so test count is same whether browser passes or fails
cleanup handling of asserts in checking for report existence and contents
remove dead, unreachable code not relevant to test case
use assert_unreached
removed trailing whitespace
removed console.log statements
whitespace
insignificant code style issue repeating an built-in identifier 2x in one-liner
whitespace
whitespace
restructured xhr event handler to user step_func