Add end to end test for Media galleries scan API.

chrome/browser/extensions/api/media_galleries/media_galleries_api.h

Index: chrome/browser/extensions/api/media_galleries/media_galleries_api.h
diff --git a/chrome/browser/extensions/api/media_galleries/media_galleries_api.h b/chrome/browser/extensions/api/media_galleries/media_galleries_api.h
index eff3e0c6a5774c180982a387d15e06fc78b152c7..4d7a15296841de2b038733bf5fcac1dfc440aa46 100644
--- a/chrome/browser/extensions/api/media_galleries/media_galleries_api.h
+++ b/chrome/browser/extensions/api/media_galleries/media_galleries_api.h
@@ -11,6 +11,7 @@
 #include <string>
 #include <vector>
 
+#include "base/callback_forward.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
 #include "chrome/browser/extensions/api/profile_keyed_api_factory.h"
@@ -22,8 +23,16 @@
 
 namespace MediaGalleries = extensions::api::media_galleries;
 
+class MediaGalleriesScanResultDialogController;
+
+namespace content {
+class WebContents;
+}
+
 namespace extensions {
 
+class Extension;
+
 // The profile-keyed service that manages the media galleries extension API.
 // Created at the same time as the Profile. This is also the event router.
 class MediaGalleriesEventRouter : public ProfileKeyedAPI,
@@ -205,6 +214,12 @@ class MediaGalleriesAddScanResultsFunction
   virtual ~MediaGalleriesAddScanResultsFunction();
   virtual bool RunImpl() OVERRIDE;
 
+  // Pulled out for testing.
+  virtual MediaGalleriesScanResultDialogController* MakeDialog(
+      content::WebContents* web_contents,
+      const extensions::Extension& extension,
+      const base::Closure& on_finish);
+
  private:
   // Bottom half for RunImpl, invoked after the preferences is initialized.
   void OnPreferencesInit();