Include USB printers in printer list as "provisional" devices.

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 9995184afd6a0b8c6d794aa1721b2c9b3fa96feb..5f3d1bb2efa8e3850f7a671551fce147987c02b4 100644
--- a/chrome/browser/ui/webui/print_preview/extension_printer_handler.h
+++ b/chrome/browser/ui/webui/print_preview/extension_printer_handler.h
@@ -6,6 +6,7 @@
 #define CHROME_BROWSER_UI_WEBUI_PRINT_PREVIEW_EXTENSION_PRINTER_HANDLER_H_
 
 #include <string>
+#include <vector>
 
 #include "base/macros.h"
 #include "base/memory/scoped_ptr.h"
@@ -29,6 +30,10 @@ namespace cloud_devices {
 class CloudDeviceDescription;
 }
 
+namespace device {
+class UsbDevice;
+}
+
 namespace gfx {
 class Size;
 }
@@ -93,7 +98,7 @@ class ExtensionPrinterHandler : public PrinterHandler {
   // They just propagate results to callbacks passed to them.
   void WrapGetPrintersCallback(
       const PrinterHandler::GetPrintersCallback& callback,
-      const base::ListValue& pritners,
+      const base::ListValue& printers,
       bool done);
   void WrapGetCapabilityCallback(
       const PrinterHandler::GetCapabilityCallback& callback,
@@ -102,10 +107,14 @@ class ExtensionPrinterHandler : public PrinterHandler {
   void WrapPrintCallback(const PrinterHandler::PrintCallback& callback,
                          bool success,
                          const std::string& status);
+  void OnUsbDevicesEnumerated(
+      const PrinterHandler::GetPrintersCallback& callback,
+      const std::vector<scoped_refptr<device::UsbDevice>>& devices);
 
   content::BrowserContext* browser_context_;
 
   scoped_ptr<local_discovery::PWGRasterConverter> pwg_raster_converter_;
+  int pending_enumeration_count_ = 0;
 
   scoped_refptr<base::TaskRunner> slow_task_runner_;