Add onGetUsbPrinterInfoRequested event to printerProvider API.

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

Index: chrome/browser/ui/webui/print_preview/extension_printer_handler.h
diff --git a/chrome/browser/ui/webui/print_preview/extension_printer_handler.h b/chrome/browser/ui/webui/print_preview/extension_printer_handler.h
index de0d473353d2f9842860a9f060ccb25fd94e4219..c9b3a2bb5b93671fb5482b320039d63c8480ab8d 100644
--- a/chrome/browser/ui/webui/print_preview/extension_printer_handler.h
+++ b/chrome/browser/ui/webui/print_preview/extension_printer_handler.h
@@ -50,6 +50,8 @@ class ExtensionPrinterHandler : public PrinterHandler {
       base::Callback<void(const base::ListValue& printers)>;
   using PrintJobCallback =
       base::Callback<void(scoped_ptr<extensions::PrinterProviderPrintJob>)>;
+  using GrantUsbPrinterAccessCallback =
+      base::Callback<void(const base::DictionaryValue& printer_info)>;
 
   ExtensionPrinterHandler(
       content::BrowserContext* browser_context,
@@ -73,6 +75,10 @@ class ExtensionPrinterHandler : public PrinterHandler {
                   const gfx::Size& page_size,
                   const scoped_refptr<base::RefCountedMemory>& print_data,
                   const PrinterHandler::PrintCallback& callback) override;
+  void StartGrantUsbPrinterAccess(
+      const std::string& extension_id,
+      int device_id,
+      const GrantUsbPrinterAccessCallback& callback);
 
  private:
   friend class ExtensionPrinterHandlerTest;
@@ -110,6 +116,10 @@ class ExtensionPrinterHandler : public PrinterHandler {
   void WrapPrintCallback(const PrinterHandler::PrintCallback& callback,
                          bool success,
                          const std::string& status);
+  void WrapGrantUsbPrinterAccessCallback(
+      const GrantUsbPrinterAccessCallback& callback,
+      const base::DictionaryValue& printer_info);
+
   void OnUsbDevicesEnumerated(
       const GetUsbPrintersCallback& callback,
       const std::vector<scoped_refptr<device::UsbDevice>>& devices);