Fix crash in HTMLInputElement::setupDateTimeChooserParameters

LayoutTests/fast/forms/datepicker-crash-after-keydown.html

Index: LayoutTests/fast/forms/datepicker-crash-after-keydown.html
diff --git a/LayoutTests/fast/forms/datepicker-crash-after-keydown.html b/LayoutTests/fast/forms/datepicker-crash-after-keydown.html
new file mode 100644
index 0000000000000000000000000000000000000000..a00b88710015e8c170ece125d7ee57e533ce3461
--- /dev/null
+++ b/LayoutTests/fast/forms/datepicker-crash-after-keydown.html
@@ -0,0 +1,19 @@
+  <input id="month" type="month"</div>

[tkent, 2014/07/30 23:19:57]

- The top level indentation is not helpful.
- Please move this to fast/forms/calendar-picker/.

+  <script>
+    if (window.testRunner) {
+      testRunner.dumpAsText();
+    }
+    function openPicker(input) {
+      sendKey(input, "Down", false, true);
+      finishTest();
+    }
+    function sendKey(input, keyName, ctrlKey, altKey) {
+      var event = document.createEvent('KeyboardEvent');
+      event.initKeyboardEvent('keydown', true, true, document.defaultView, keyName, 0, ctrlKey, altKey);
+      input.dispatchEvent(event);
+    }
+    openPicker(document.getElementById('month'), finishTest);
+    function finishTest() {
+      document.body.innerText = 'PASS (not crashed)';
+    }
+  </script>