[CUPS] Change manufacturer selection should clear model selection in the dropdown list.

chrome/browser/resources/settings/printing_page/cups_add_printer_dialog_util.html

 <link rel="import" href="chrome://resources/cr_elements/cr_dialog/cr_dialog.html">
 <link rel="import" href="chrome://resources/cr_elements/icons.html">
 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-dropdown/iron-dropdown.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-input/iron-input.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-button/paper-button.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-icon-button/paper-icon-button.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-input/paper-input-container.html">
 <link rel="import" href="cups_printers_browser_proxy.html">
 <link rel="import" href="../settings_shared_css.html">
@@ skipping 59 matching lines @@
       }
 
       iron-dropdown .dropdown-content {
         background-color: white;
         box-shadow: 0 2px 6px var(--paper-grey-500);
         min-width: 128px;
         padding: 8px 0;
       }
     </style>
     <paper-input-container no-label-float on-tap="onTap_">
-      <input is="iron-input" type="search"
+      <input is="iron-input" type="search" bind-value="{{selectedItem}}"
           on-search="onInputValueChanged_" on-change="onChange_" incremental>
       <paper-icon-button suffix id="searchIcon" icon="cr:search" hidden>
       </paper-icon-button>
       <paper-icon-button suffix id="dropdownIcon" icon="cr:arrow-drop-down">
       </paper-icon-button>
     </paper-input-container>
     <iron-dropdown horizontal-align="left" vertical-align="top"
         vertical-offset="47">
       <div class="dropdown-content">
         <template is="dom-repeat" items="[[items]]"
@@ skipping 28 matching lines @@
       <div class="body">
         <content select=".dialog-body"></content>
       </div>
       <div class="button-container">
         <content select=".dialog-buttons"></content>
       </div>
     </dialog>
   </template>
   <script src="cups_add_printer_dialog_util.js"></script>
 </dom-module>