Migrated several tests from blink to V8 repository.

test/webkit/dfg-to-string-toString-becomes-bad-with-check-structure.js

Index: test/webkit/dfg-to-string-toString-becomes-bad-with-check-structure.js
diff --git a/test/webkit/concat-while-having-a-bad-time.js b/test/webkit/dfg-to-string-toString-becomes-bad-with-check-structure.js
similarity index 80%
copy from test/webkit/concat-while-having-a-bad-time.js
copy to test/webkit/dfg-to-string-toString-becomes-bad-with-check-structure.js
index dfda1e08a0b36194b787a44ee12a9693acd8aeaf..e37fa99b5a1be2a48109d7a071a0ad8d9b69ca28 100644
--- a/test/webkit/concat-while-having-a-bad-time.js
+++ b/test/webkit/dfg-to-string-toString-becomes-bad-with-check-structure.js
@@ -22,10 +22,16 @@
 // SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 description(
-"Tests the behavior of Array.prototype.concat while the array is having a bad time due to one of the elements we are concatenating."
+"Tests that the DFG checks that the toString method didn't become bad even if the StringObject already had a CheckStructure."
 );
 
-Object.defineProperty(Array.prototype, 0, { writable: false });
-shouldBe("[42].concat()", "[42]");
+function foo() {
+    return String(this);
+}
 
+for (var i = 0; i < 100; ++i) {
+    if (i == 99)
+        String.prototype.toString = function() { return 42; }
+    shouldBe("foo.call(new String(\"foo\"))", i >= 99 ? "\"42\"" : "\"foo\"");
+}