Update CUPS settings UI to allow USB printers to be added via discovery.

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

 <link rel="import" href="chrome://resources/html/md_select_css.html">
 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="chrome://resources/html/web_ui_listener_behavior.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-input/paper-input.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-spinner/paper-spinner.html">
 <link rel="import" href="../i18n_setup.html">
 <link rel="import" href="cups_add_printer_dialog_util.html">
 <link rel="import" href="cups_printers_browser_proxy.html">
 <link rel="import" href="../settings_shared_css.html">
@@ skipping 57 matching lines @@
             $i18n{manuallyAddPrinterButtonText}
           </paper-button>
         </div>
         <div>  <!-- Right group -->
           <paper-button class="cancel-button secondary-button"
               on-tap="onCancelTap_">
             $i18n{cancelButtonText}
           </paper-button>
           <paper-button class="action-button" id="addPrinterButton"
               disabled="[[!selectedPrinter]]"
-              on-tap="switchToConfiguringDialog_">
+              on-tap="switchToManufacturerDialog_">
             $i18n{addPrinterButtonText}
           </paper-button>
         </div>
       </div>
     </add-printer-dialog>
   </template>
 </dom-module>
 
 <dom-module id="add-printer-manually-dialog">
   <template>
@@ skipping 221 matching lines @@
             </div>
           </div>
         </div>
         <div class="error-message" hidden="[[!setupFailed]]">
           Driver not found (exact error message TBD)
         </div>
       </div>
       <div class="dialog-buttons">
         <div>  <!-- Left group -->
           <paper-button id="manuallyAddPrinterButton" class="secondary-button"
-              on-tap="switchToManualAddDialog_">
-            $i18n{manuallyAddPrinterButtonText}
+              on-tap="switchToManualAddDialog_" hidden="[[!inManualFlow]]">

[xdai1, 2017/05/11 00:25:10]

Unrelated question: If we want to modify this button to be a back button, why
don't we have it for discovery flow as well? Clicking on the back button either
directs the user to the manual dialog or to the discovery dialog seems more
reasonable? (btw: was weifangsun@ aware of this button change?)

[Carlson, 2017/05/11 22:08:58]

Good point on both parts.

We discussed options offline.  I've pinged, but haven't heard back from Weifang,
but I'd really like to get the top level change in for M60, so for now I've
implemented this as 'back' in both the discovery and manual case, which is sort
of the minimal change that makes things orthogonal.  I recognize that we may
change this ui decision later, but I think it's not worth holding up the change?

+            $i18n{back}
           </paper-button>
         </div>
         <div>  <!-- Right group -->
           <paper-button class="cancel-button secondary-button"
               on-tap="onCancelTap_">
             $i18n{cancelButtonText}
           </paper-button>
           <paper-button class="action-button" id="addPrinterButton"
               on-tap="switchToConfiguringDialog_">
             $i18n{addPrinterButtonText}
@@ skipping 48 matching lines @@
     <template is="dom-if" if="[[showConfiguringDialog_]]" restamp>
       <add-printer-configuring-dialog
           printer-name="[[getConfiguringPrinterName_()]]"
           dialog-title="[[configuringDialogTitle]]">
       </add-printer-configuring-dialog>
     </template>
 
     <!-- Manufacturer and Model Dialog -->
     <template is="dom-if" if="[[showManufacturerDialog_]]" restamp>
       <add-printer-manufacturer-model-dialog new-printer="{{newPrinter}}"
-          setup-failed="[[setupFailed]]">
+          selected-printer="{{selectedPrinter}}" setup-failed="[[setupFailed]]"
+          in-manual-flow="[[inManualFlow]]">
       </add-printer-manufacturer-model-dialog>
     </template>
 
   </template>
   <script src="cups_add_printer_dialog.js"></script>
 </dom-module>