Added TodoMVC startup benchmarks.

samples/third_party/todomvc_performance/js_todomvc/elements/td-input.html

+<link rel="import" href="../components/polymer/polymer.html">
+
+<polymer-element name="td-input" extends="input" on-keyup="{{keyupAction}}" on-keypress="{{keypressAction}}">
+        <script>
+                (function() {
+                        var ENTER_KEY = 13;
+                        var ESC_KEY = 27;
+                        Polymer('td-input', {
+                                keypressAction: function(e, detail, sender) {
+                                        // Listen for enter on keypress but esc on keyup, because
+                                        // IE doesn't fire keyup for enter.
+                                        if (e.keyCode === ENTER_KEY) {
+                                                this.fire('td-input-commit');
+                                        }
+                                },
+                                keyupAction: function(e, detail, sender) {
+                                        if (e.keyCode === ESC_KEY) {
+                                                this.fire('td-input-cancel');
+                                        }
+                                }
+                        });
+                })();
+        </script>
+</polymer-element>