Add onGetUsbPrinterInfoRequested event to printerProvider API.

extensions/common/api/printer_provider.idl

 // Copyright 2014 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.
 
 // The <code>chrome.printerProvider</code> API exposes events used by print
 // manager to query printers controlled by extensions, to query their
 // capabilities and to submit print jobs to these printers.
 namespace printerProvider {
   // Error codes returned in response to $(ref:onPrintRequested) event.
   enum PrintError {
@@ skipping 42 matching lines @@
     // <code>"application/pdf"</code> and <code>"image/pwg-raster"</code>.
     DOMString contentType;
 
     // Blob containing the document data to print. Format must match
     // |contentType|.
     [instanceOf=Blob] object document;
   };
 
   callback PrintersCallback = void(PrinterInfo[] printerInfo);
 
+  callback PrinterInfoCallback = void(optional PrinterInfo printerInfo);
+
   // |capabilities|: Device capabilities in
   // <a href="https://developers.google.com/cloud-print/docs/cdd#cdd">CDD
   // format</a>.
   callback CapabilitiesCallback = void(object capabilities);
 
   callback PrintCallback = void(PrintError result);
 
   interface Events {
     // Event fired when print manager requests printers provided by extensions.
     // |resultCallback|: Callback to return printer list. Every listener must
     // call callback exactly once.
     static void onGetPrintersRequested(PrintersCallback resultCallback);
 
+    // Event fired when print manager requests information about a USB device
+    // that may be a printer.
+    // <p><em>Note:</em> An application should not rely on this event being
+    // fired more than once per device. If a connected device is supported it
+    // should be returned in the $(ref:onGetPrintersRequested) event.</p>
+    // |device|: The USB device.
+    // |resultCallback|: Callback to return printer info. The receiving listener
+    // must call callback exactly once. If the parameter to this callback is
+    // undefined that indicates that the application has determined that the
+    // device is not supported.
+    static void onGetUsbPrinterInfoRequested(
+        usb.Device device,
+        PrinterInfoCallback resultCallback);
+
     // Event fired when print manager requests printer capabilities.
     // |printerId|: Unique ID of the printer whose capabilities are requested.
     // |resultCallback|: Callback to return device capabilities in
     // <a href="https://developers.google.com/cloud-print/docs/cdd#cdd">CDD
     // format</a>.
     // The receiving listener must call callback exectly once.
     static void onGetCapabilityRequested(DOMString printerId,
                                          CapabilitiesCallback resultCallback);
 
     // Event fired when print manager requests printing.
     // |printJob|: The printing request parameters.
     // |resultCallback|: Callback that should be called when the printing
     // request is completed.
     static void onPrintRequested(PrintJob printJob,
                                  PrintCallback resultCallback);
   };
 };