Insert missing type cast in JSON.stringify.

test/mjsunit/regress/regress-2570.js

Index: test/mjsunit/regress/regress-2570.js
diff --git a/test/mjsunit/regress/regress-crbug-172345.js b/test/mjsunit/regress/regress-2570.js
similarity index 90%
copy from test/mjsunit/regress/regress-crbug-172345.js
copy to test/mjsunit/regress/regress-2570.js
index 711501caa791f2974635ac4dd894568a2e3fc982..e7d5c12a480af057d14e6ace4e3e9a399e3025ed 100644
--- a/test/mjsunit/regress/regress-crbug-172345.js
+++ b/test/mjsunit/regress/regress-2570.js
@@ -25,10 +25,7 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-function f(a,i) {
-  return a[i];
-}
+var o = ["\u56e7",   // Switch JSON stringifier to two-byte mode.
+         "\u00e6"];  // Latin-1 character.
 
-f([1,2,3], "length");
-f([1,2,3], "length");
-f([1,2,3], 2);
+assertEquals(JSON.stringify(o, null, 0), JSON.stringify(o));