MD WebUI: Use dom-if to control hidden elements in <cr-toolbar>

ui/webui/resources/cr_elements/cr_toolbar/cr_toolbar_search_field.js

 // Copyright 2016 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.
 
 // TODO(tsergeant): Add tests for cr-toolbar-search-field.
 Polymer({
   is: 'cr-toolbar-search-field',
 
   behaviors: [CrSearchFieldBehavior],
 
@@ skipping 11 matching lines @@
 
     // When true, show a loading spinner to indicate that the backend is
     // processing the search. Will only show if the search field is open.
     spinnerActive: {
       type: Boolean,
       reflectToAttribute: true
     },
 
     /** @private */
     hasSearchText_: Boolean,
+
+    isSpinnerShown_: {
+      type: Boolean,
+      computed: 'computeIsSpinnerShown_(spinnerActive, showingSearch)'
+    }
   },
 
   listeners: {
     'tap': 'showSearch_',
     'searchInput.bind-value-changed': 'onBindValueChanged_',
   },
 
   /** @return {!HTMLInputElement} */
   getSearchInput: function() {
     return this.$.searchInput;
   },
 
   /** @return {boolean} */
   isSearchFocused: function() {
     return this.$.searchTerm.focused;
   },
 
   /**
    * @param {boolean} narrow
    * @return {number}
    * @private
    */
   computeIconTabIndex_: function(narrow) {
     return narrow ? 0 : -1;
   },
 
   /**
-   * @param {boolean} spinnerActive
-   * @param {boolean} showingSearch
    * @return {boolean}
    * @private
    */
-  isSpinnerShown_: function(spinnerActive, showingSearch) {
-    return spinnerActive && showingSearch;
+  computeIsSpinnerShown_: function() {
+    return this.spinnerActive && this.showingSearch;
   },
 
   /** @private */
   onInputBlur_: function() {
     if (!this.hasSearchText_)
       this.showingSearch = false;
   },
 
   /**
    * Update the state of the search field whenever the underlying input value
@@ skipping 19 matching lines @@
 
   /**
    * @param {Event} e
    * @private
    */
   hideSearch_: function(e) {
     this.showingSearch = false;
     e.stopPropagation();
   }
 });