Lazy call to custom stack trace formatting using Error.prepareStackTrace.

test/mjsunit/stack-traces-custom-lazy.js

Index: test/mjsunit/stack-traces-custom-lazy.js
diff --git a/test/intl/date-format/format-test.js b/test/mjsunit/stack-traces-custom-lazy.js
similarity index 76%
copy from test/intl/date-format/format-test.js
copy to test/mjsunit/stack-traces-custom-lazy.js
index 9817c97ed975283f2313e7b1ece8a0b110365e84..91d97f3739dc746434731352a0ec7ade0d839484 100644
--- a/test/intl/date-format/format-test.js
+++ b/test/mjsunit/stack-traces-custom-lazy.js
@@ -25,22 +25,25 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-// Test formatting method with specified date, invalid input.
-
-var dtf = new Intl.DateTimeFormat('en-US', {timeZone: 'UTC'});
-
-var someDate = dtf.format(144313200000);
-assertEquals('7/29/1974', someDate);
-
-var invalidValues = [NaN, Infinity, -Infinity];
-invalidValues.forEach(function(value) {
-  var error;
+function testPrepareStackTrace(closure) {
+  var error = undefined;
   try {
-    dtf.format(value);
+    closure();
+    assertUnreachable();
   } catch (e) {
     error = e;
   }
 
-  assertTrue(error !== undefined);
-  assertEquals('RangeError', error.name);
-});
+  // We expect custom formatting to be lazy. Setting the custom
+  // function right before calling error.stack should be fine.
+  Error.prepareStackTrace = function(e, frames) {
+    return "bar";
+  }
+
+  assertEquals("bar", error.stack);
+  Error.prepareStackTrace = undefined;
+}
+
+testPrepareStackTrace(function() { throw new Error("foo"); });
+testPrepareStackTrace(function f() { f(); });
+