Add onGetUsbPrinterInfoRequested event to printerProvider API.

extensions/common/api/printer_provider.idl

Index: extensions/common/api/printer_provider.idl
diff --git a/extensions/common/api/printer_provider.idl b/extensions/common/api/printer_provider.idl
index 40a07c5f5be874813d353c37288c2f70eb223c1d..aa1e31e17cf3e06ca4b9355c000af5eef0ce976d 100644
--- a/extensions/common/api/printer_provider.idl
+++ b/extensions/common/api/printer_provider.idl
@@ -34,6 +34,10 @@ namespace printerProvider {
 
     // Printer's human readable description.
     DOMString? description;
+
+    // USB device corresponding to this printer. This should be the
+    // opaque ID found in the $(ref:usb.Device) dictionary.
+    long? usbDevice;
   };
 
   // Printing request parameters. Passed to $(ref:onPrintRequested) event.
@@ -60,6 +64,8 @@ namespace printerProvider {
 
   callback PrintersCallback = void(PrinterInfo[] printerInfo);
 
+  callback PrinterInfoCallback = void(PrinterInfo printerInfo);
+
   // |capabilities|: Device capabilities in
   // <a href="https://developers.google.com/cloud-print/docs/cdd#cdd">CDD
   // format</a>.
@@ -73,6 +79,15 @@ namespace printerProvider {
     // call callback exactly once.
     static void onGetPrintersRequested(PrintersCallback resultCallback);
 
+    // Event fired when print manager grants access to a USB device.
+    // |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

[Vitaly Buka (NO REVIEWS), 2015/05/21 00:52:02]

Looks like this even should be in chrome.usb

Idea was to have printerProvider independent form printer implementation.

[Reilly Grant (use Gerrit), 2015/05/21 00:58:22]

I could add this event to chrome.usb but I would no longer want it to provide a
PrinterInfoCallback. Instead I would add a printerAdded function to
chrome.printerProvider so that providers could add printers to the print preview
dialog outside the context of an enumeration. This would also be useful for when
a printer is connected after the print dialog is opened. What do you think?

+    // device is not supported.
+    static void onUsbAccessGranted(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