Add onGetUsbPrinterInfoRequested event to printerProvider API.

chrome/browser/ui/webui/print_preview/extension_printer_handler.cc

Index: chrome/browser/ui/webui/print_preview/extension_printer_handler.cc
diff --git a/chrome/browser/ui/webui/print_preview/extension_printer_handler.cc b/chrome/browser/ui/webui/print_preview/extension_printer_handler.cc
index b5d2feb599b3dad353f8883f1fc3c6e4f3a5f7fb..0a5a362f4feb39843f942e37525bda820ddc595a 100644
--- a/chrome/browser/ui/webui/print_preview/extension_printer_handler.cc
+++ b/chrome/browser/ui/webui/print_preview/extension_printer_handler.cc
@@ -191,6 +191,19 @@ void ExtensionPrinterHandler::StartPrint(
                                 weak_ptr_factory_.GetWeakPtr(), callback));
 }
 
+void ExtensionPrinterHandler::StartGrantUsbPrinterAccess(
+    const std::string& extension_id,
+    int device_id,
+    const GrantUsbPrinterAccessCallback& callback) {
+  extensions::PrinterProviderAPIFactory::GetInstance()
+      ->GetForBrowserContext(browser_context_)
+      ->DispatchGrantUsbPrinterAccess(
+          extension_id, device_id,
+          base::Bind(
+              &ExtensionPrinterHandler::WrapGrantUsbPrinterAccessCallback,
+              weak_ptr_factory_.GetWeakPtr(), callback));
+}
+
 void ExtensionPrinterHandler::SetPwgRasterConverterForTesting(
     scoped_ptr<local_discovery::PWGRasterConverter> pwg_raster_converter) {
   pwg_raster_converter_ = pwg_raster_converter.Pass();
@@ -250,6 +263,12 @@ void ExtensionPrinterHandler::WrapPrintCallback(
   callback.Run(success, status);
 }
 
+void ExtensionPrinterHandler::WrapGrantUsbPrinterAccessCallback(
+    const GrantUsbPrinterAccessCallback& callback,
+    const base::DictionaryValue& printer_info) {
+  callback.Run(printer_info);
+}
+
 void ExtensionPrinterHandler::OnUsbDevicesEnumerated(
     const GetUsbPrintersCallback& callback,
     const std::vector<scoped_refptr<UsbDevice>>& devices) {