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..de0d473353d2f9842860a9f060ccb25fd94e4219 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;
 }
@@ -41,6 +46,8 @@ class PWGRasterConverter;
 // extension API.
 class ExtensionPrinterHandler : public PrinterHandler {
  public:
+  using GetUsbPrintersCallback =
+      base::Callback<void(const base::ListValue& printers)>;
   using PrintJobCallback =
       base::Callback<void(scoped_ptr<extensions::PrinterProviderPrintJob>)>;
 
@@ -54,6 +61,7 @@ class ExtensionPrinterHandler : public PrinterHandler {
   void Reset() override;
   void StartGetPrinters(
       const PrinterHandler::GetPrintersCallback& callback) override;
+  void StartGetUsbPrinters(const GetUsbPrintersCallback& callback);
   void StartGetCapability(
       const std::string& destination_id,
       const PrinterHandler::GetCapabilityCallback& calback) override;
@@ -93,7 +101,7 @@ 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,
@@ -102,6 +110,9 @@ class ExtensionPrinterHandler : public PrinterHandler {
   void WrapPrintCallback(const PrinterHandler::PrintCallback& callback,
                          bool success,
                          const std::string& status);
+  void OnUsbDevicesEnumerated(
+      const GetUsbPrintersCallback& callback,
+      const std::vector<scoped_refptr<device::UsbDevice>>& devices);
 
   content::BrowserContext* browser_context_;