Eliminate globalFlag usage from http security layout tests.

LayoutTests/http/tests/security/aboutBlank/xss-DENIED-set-opener-expected.txt

 CONSOLE ERROR: line 1: Uncaught SecurityError: Blocked a frame with origin "http://127.0.0.1:8000" from accessing a frame with origin "http://localhost:8000". Protocols, domains, and ports must match.
 This page opens a window to "", injects malicious code, and then uses window.open.call to set its opener to the victim. The opened window then tries to scripts its opener.
 Code injected into window:
 <script>function write(target, message) { target.document.body.innerHTML = message; }
 setTimeout(function() {write(window.opener.top.frames[0], 'FAIL: XSS was allowed.');}, 100);
 setTimeout(function() {write(window.opener.top.frames[1], 'SUCCESS: Window remained in original SecurityOrigin.');}, 200);
-setTimeout(function() { if (window.testRunner) testRunner.globalFlag = true; }, 300);</script>
+setTimeout(function() { window.opener.top.postMessage('done', '*'); }, 300);</script>
 PASS: 'window.open' called on another frame threw: SecurityError: Failed to execute 'open' on 'Window': Blocked a frame with origin "http://127.0.0.1:8000" from accessing a cross-origin frame.
  
 
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 Frame: '<!--framePath //<!--frame0-->-->'
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 This page doesn't do anything special.
 
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 Frame: '<!--framePath //<!--frame1-->-->'
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 SUCCESS: Window remained in original SecurityOrigin.