Explicit GC of strings to avoid test timeout.

LayoutTests/fast/css/visited-link-hang.html

 <p>If this test runs without hanging, then it has passed. The visited link hash algorithm was N^2 at one point and would hang.</p>
 <p id="test1"></p>
 <p id="test2"></p>
 <p id="test3"></p>
 <p id="result">TEST DID NOT RUN YET</p>
 
 <script>
 
 if (window.testRunner)
     testRunner.dumpAsText();
 
 var oneMillionSlashes = "";
 for (i = 0; i < 1000000; ++i)
     oneMillionSlashes += "/";
 
 var oneMillionSlashesAndDots = "";
 for (i = 0; i < 333334; ++i)
     oneMillionSlashesAndDots += "/./";
 
 var oneMillionSlashesAndDoubleDots = "";
 for (i = 0; i < 250000; ++i)
     oneMillionSlashesAndDoubleDots += "/../";
 
 document.getElementById("test1").innerHTML = '<a href="about:test?slashes' + oneMillionSlashes + '">Link with tons of slashes</a>';
 document.getElementById("test2").innerHTML = '<a href="about:test?slashes' + oneMillionSlashesAndDots + '">Link with tons of slashes with dots</a>';
 document.getElementById("test3").innerHTML = '<a href="about:test?slashes' + oneMillionSlashesAndDoubleDots + '">Link with tons of slashes with double dots</a>';
 
+// GC these large strings so that they don't cause the next test to timeout.
+if (window.GCController) {
+    oneMillionSlashes = null;
+    oneMillionSlashesAndDots = null;
+    oneMillionSlashesAndDoubleDots = null;
+    GCController.collect();
+}
+
 document.getElementById("result").firstChild.data = "TEST PASSED";
-
 </script>