Use the media galleries controller interface for the scan result dialog.

chrome/browser/ui/cocoa/extensions/media_galleries_dialog_cocoa.mm

Index: chrome/browser/ui/cocoa/extensions/media_galleries_dialog_cocoa.mm
diff --git a/chrome/browser/ui/cocoa/extensions/media_galleries_dialog_cocoa.mm b/chrome/browser/ui/cocoa/extensions/media_galleries_dialog_cocoa.mm
index e52c6829699190a8303ee9aa0c27b0181416e54d..dda6c98f6d44212e78df4d6aa5b3277ae254e764 100644
--- a/chrome/browser/ui/cocoa/extensions/media_galleries_dialog_cocoa.mm
+++ b/chrome/browser/ui/cocoa/extensions/media_galleries_dialog_cocoa.mm
@@ -109,6 +109,10 @@ MediaGalleriesDialogCocoa::MediaGalleriesDialogCocoa(
 MediaGalleriesDialogCocoa::~MediaGalleriesDialogCocoa() {
 }
 
+void MediaGalleriesDialogCocoa::AcceptDialogForTesting() {
+  OnAcceptClicked();
+}
+
 void MediaGalleriesDialogCocoa::InitDialogControls() {
   main_container_.reset([[NSBox alloc] init]);
   [main_container_ setBoxType:NSBoxCustom];