Migrate more tests from blink repository.

test/webkit/fast/js/date-negative-setmonth.js

Index: test/webkit/fast/js/date-negative-setmonth.js
diff --git a/test/webkit/array-tostring-and-join.js b/test/webkit/fast/js/date-negative-setmonth.js
similarity index 85%
copy from test/webkit/array-tostring-and-join.js
copy to test/webkit/fast/js/date-negative-setmonth.js
index b4fdb51b47f0b450a53fc725a133c27a21c5375d..8fcd73d694378353e0f4178fb70e4c52ad22b1fb 100644
--- a/test/webkit/array-tostring-and-join.js
+++ b/test/webkit/fast/js/date-negative-setmonth.js
@@ -22,15 +22,9 @@
 // SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 description(
-
-"This test checks that toString and join share the same HashSet for visited elements."
-
+'This test checks for a regression against <a href="https://bugs.webkit.org/show_bug.cgi?id=5280">Date.setMonth fails with negative values</a>.'
 );
 
-var arr = [1, 2];
-var obj = {};
-obj.__proto__.toString = function() { return "*" + arr + "*"; }
-arr[2] = arr;
-arr[3] = obj;
-
-shouldBe("arr.join()", "'1,2,,**'");
+var d = new Date(2005, 6, 15);
+d.setMonth(-3);
+shouldBe("d.valueOf()", "new Date(2004, 9, 15).valueOf()");