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 3236e3ecda46426e5261994ef313b501b8fbc0f7..a1205902794f789af8fb4e92848b7a6329bce9c8 100644
--- a/chrome/browser/ui/webui/print_preview/extension_printer_handler.cc
+++ b/chrome/browser/ui/webui/print_preview/extension_printer_handler.cc
@@ -150,6 +150,19 @@ 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();
@@ -208,3 +221,9 @@ void ExtensionPrinterHandler::WrapPrintCallback(
     const std::string& status) {
   callback.Run(success, status);
 }
+
+void ExtensionPrinterHandler::WrapGrantUsbPrinterAccessCallback(
+    const GrantUsbPrinterAccessCallback& callback,
+    const base::DictionaryValue& printer_info) {
+  callback.Run(printer_info);
+}