Add onGetUsbPrinterInfoRequested event to printerProvider API.

extensions/browser/api/printer_provider_internal/printer_provider_internal_api_observer.h

Index: extensions/browser/api/printer_provider_internal/printer_provider_internal_api_observer.h
diff --git a/extensions/browser/api/printer_provider_internal/printer_provider_internal_api_observer.h b/extensions/browser/api/printer_provider_internal/printer_provider_internal_api_observer.h
index 02cbacd8a620bd4bbec0b3cd4bd42b40526845d8..27b8ee71ab1b92f268356df97d25fe5839d1b2a4 100644
--- a/extensions/browser/api/printer_provider_internal/printer_provider_internal_api_observer.h
+++ b/extensions/browser/api/printer_provider_internal/printer_provider_internal_api_observer.h
@@ -53,6 +53,16 @@ class PrinterProviderInternalAPIObserver {
       int request_id,
       core_api::printer_provider_internal::PrintError error) = 0;
 
+  // Used by chrome.printerProviderInternal API to report
+  // chrome.printerProvider.onGetUsbPrinterInfoRequested result returned by the
+  // extension |extension|.
+  // |request_id| is the request id passed to the original
+  // chrome.printerProvider.onGetUsbPrinterInfoRequested event.
+  virtual void OnGetUsbPrinterInfoResult(
+      const Extension* extension,
+      int request_id,
+      const core_api::printer_provider::PrinterInfo* printer_info) = 0;
+
  protected:
   virtual ~PrinterProviderInternalAPIObserver() {}
 };