fix(input): Firefox validation trigger

Do not trigger Firefox validation on form initialization.
- Do not set a value to an <input> field if the field already has the same value

Closes #12102

Author: lgalfaso

src/ng/directive/input.js

@@ -1128,7 +1128,11 @@ function baseInputType(scope, element, attr, ctrl, $sniffer, $browser) {
   element.on('change', listener);
 
   ctrl.$render = function() {
-    element.val(ctrl.$isEmpty(ctrl.$viewValue) ? '' : ctrl.$viewValue);
+    // Workaround for Firefox validation #12102.
+    var value = ctrl.$isEmpty(ctrl.$viewValue) ? '' : ctrl.$viewValue;
+    if (element.val() !== value) {
+      element.val(value);
+    }
   };
 }