fix(input): don't perform HTML5 validation on updated model-value

Running html5-validation immediately after model-value is updated is incorrect, because the view
has not updated, and HTML5 constraint validation has not adjusted. This should be properly fixed
later on by performing html5 validation after the view value is updated, and a comment has been
left to address this in the future.

Closes angular#6796

src/ng/directive/input.js

@@ -874,7 +874,7 @@ function addNativeHtml5Validators(ctrl, validatorName, element) {
       return value;
     };
     ctrl.$parsers.push(validator);
-    ctrl.$formatters.push(validator);
+    // TODO: perform HTML5 validation after $formatters are run and $viewValue updated
   }
 }