Add onGetUsbPrinterInfoRequested event to printerProvider API.

extensions/browser/api/printer_provider/printer_provider_api.h

Index: extensions/browser/api/printer_provider/printer_provider_api.h
diff --git a/extensions/browser/api/printer_provider/printer_provider_api.h b/extensions/browser/api/printer_provider/printer_provider_api.h
index f499e5ecc88dbe0c75ec829c3d74ab2e118d1d91..33a078353a097e5c573fa7e80228b0f4744570e4 100644
--- a/extensions/browser/api/printer_provider/printer_provider_api.h
+++ b/extensions/browser/api/printer_provider/printer_provider_api.h
@@ -19,6 +19,10 @@ namespace content {
 class BrowserContext;
 }
 
+namespace device {
+class UsbDevice;
+}
+
 namespace extensions {
 class Extension;
 struct PrinterProviderPrintJob;
@@ -35,6 +39,8 @@ class PrinterProviderAPI : public KeyedService {
       base::Callback<void(const base::DictionaryValue& capability)>;
   using PrintCallback =
       base::Callback<void(bool success, const std::string& error)>;
+  using UsbAccessGrantedCallback =
+      base::Callback<void(const base::DictionaryValue& printer_info)>;
 
   static PrinterProviderAPI* Create(content::BrowserContext* context);
 
@@ -82,6 +88,12 @@ class PrinterProviderAPI : public KeyedService {
   // It should return NULL if the job for the request does not exist.
   virtual const PrinterProviderPrintJob* GetPrintJob(const Extension* extension,
                                                      int request_id) const = 0;
+
+  // Notifies the given extension that it has been granted access to the given
+  virtual void DispatchGrantUsbPrinterAccess(
+      const std::string& extension_id,
+      int device_id,
+      const PrinterProviderAPI::UsbAccessGrantedCallback& callback) = 0;
 };
 
 }  // namespace extensions