Add back test for user rejected value

Not sure how this got lost. Asserts that https://github.com/Polymer/NodeBind/blob/master/src/NodeBind.js#L186 is required (otherwise the element wouldn't find out that the value was put back to its initial value, because from it's observable's POV the value would not have changed).

R=arv
BUG=

Review URL: https://codereview.appspot.com/73240044

Author: rafaelw

tests/tests.js

@@ -323,7 +323,7 @@ suite('Form Element Bindings', function() {
     inputTextAreaPathUnreachable('textarea');
   });
 
-  test('Input.value - user value rejected', function(done) {
+  test('Input.value - detailed', function(done) {
     var model = {val: 'ping'};
 
     var el = testDiv.appendChild(document.createElement('input'));
@@ -379,6 +379,32 @@ suite('Form Element Bindings', function() {
     });
   });
 
+  test('Input.value - user value rejected', function(done) {
+    var model = {val: 'ping'};
+
+    var rejector = new PathObserver(model, 'val');
+    rejector.open(function() {
+      model.val = 'ping';
+    });
+
+    var el = testDiv.appendChild(document.createElement('input'));
+    el.bind('value', new PathObserver(model, 'val'));
+
+    then(function() {
+      assert.strictEqual('ping', el.value);
+
+      el.value = 'pong';
+      dispatchEvent('input', el);
+
+    }).then(function() {
+      // rejector will have set the bound value back to 'ping'.
+      assert.strictEqual('ping', el.value);
+
+      rejector.close();
+      done();
+    });
+  });
+
   test('(Checkbox)Input.checked', function(done) {
     var input = testDiv.appendChild(document.createElement('input'));
     testDiv.appendChild(input);