Fix iOS autofill JavaScript compiler warnings.

ios/web/web_state/js/resources/common.js

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // This file provides common methods that can be shared by other JavaScripts.
 
 goog.provide('__crWeb.common');
 
 goog.require('__crWeb.base');
 
 
+/** @typedef {HTMLInputElement|HTMLTextAreaElement|HTMLSelectElement} */
+var FormControlElement;
+
 /**
  * Namespace for this file. It depends on |__gCrWeb| having already been
  * injected. String 'common' is used in |__gCrWeb['common']| as it needs to be
  * accessed in Objective-C code.
  */
 __gCrWeb['common'] = {};
 
 /* Beginning of anonymous object. */
 (function() {
   /**
@@ skipping 60 matching lines @@
    * Returns an array of control elements in a form.
    *
    * This method is based on the logic in method
    *     void WebFormElement::getFormControlElements(
    *         WebVector<WebFormControlElement>&) const
    * in chromium/src/third_party/WebKit/Source/WebKit/chromium/src/
    * WebFormElement.cpp.
    *
    * @param {Element} form A form element for which the control elements are
    *   returned.
-   * @return {Array<Element>}
+   * @return {Array<FormControlElement>}
    */
   __gCrWeb.common.getFormControlElements = function(form) {
     if (!form) {
       return [];
     }
     var results = [];
     // Get input and select elements from form.elements.
     // TODO(chenyu): according to
     // http://www.w3.org/TR/2011/WD-html5-20110525/forms.html, form.elements are
     // the "listed elements whose form owner is the form element, with the
     // exception of input elements whose type attribute is in the Image Button
     // state, which must, for historical reasons, be excluded from this
     // particular collection." In WebFormElement.cpp, this method is implemented
     // by returning elements in form's associated elements that have tag 'INPUT'
     // or 'SELECT'. Check if input Image Buttons are excluded in that
     // implementation. Note for Autofill, as input Image Button is not
     // considered as autofillable elements, there is no impact on Autofill
     // feature.
     var elements = form.elements;
     for (var i = 0; i < elements.length; i++) {
       if (__gCrWeb.common.isFormControlElement(elements[i])) {
-        results.push(elements[i]);
+        results.push(/** @type {FormControlElement} */ (elements[i]));
       }
     }
     return results;
   };
 
   /**
    * Returns true if an element can be autocompleted.
    *
    * This method aims to provide the same logic as method
    *     bool autoComplete() const
@@ skipping 550 matching lines @@
     var plugins = findPluginNodesWithoutFallback_();
     if (plugins.length > 0) {
       // Store the list of plugins in a known place for the replacement script
       // to use, then trigger it.
       __gCrWeb['placeholderTargetPlugins'] = plugins;
       return true;
     }
     return false;
   };
 }());  // End of anonymous object