Implement mediaGalleriesPrivate api to notify extensions about gallery changed events.

chrome/browser/extensions/api/media_galleries_private/media_galleries_private_api_factory.cc

Index: chrome/browser/extensions/api/media_galleries_private/media_galleries_private_api_factory.cc
diff --git a/chrome/browser/extensions/api/media_galleries_private/media_galleries_private_api_factory.cc b/chrome/browser/extensions/api/media_galleries_private/media_galleries_private_api_factory.cc
index 4d4effc61c6fc7b55b88e70e0a62400a318450a5..065a3b4487f768c8b4c44f9319c2ce77c7918274 100644
--- a/chrome/browser/extensions/api/media_galleries_private/media_galleries_private_api_factory.cc
+++ b/chrome/browser/extensions/api/media_galleries_private/media_galleries_private_api_factory.cc
@@ -6,14 +6,29 @@
 
 #include "chrome/browser/extensions/api/media_galleries_private/media_galleries_private_api.h"
 #include "chrome/browser/extensions/extension_system_factory.h"
+#include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/profiles/profile_dependency_manager.h"
 
 namespace extensions {
 
+namespace {
+
+base::LazyInstance<MediaGalleriesPrivateAPIFactory>
+    g_media_galleries_private_api_factory = LAZY_INSTANCE_INITIALIZER;
+
+}  // namespace
+
 // static
 MediaGalleriesPrivateAPIFactory*
     MediaGalleriesPrivateAPIFactory::GetInstance() {
-  return Singleton<MediaGalleriesPrivateAPIFactory>::get();
+  return g_media_galleries_private_api_factory.Pointer();
+}
+
+// static
+MediaGalleriesPrivateAPI* MediaGalleriesPrivateAPIFactory::GetForProfile(
+    Profile* profile) {
+  return static_cast<MediaGalleriesPrivateAPI*>(
+      GetInstance()->GetServiceForProfile(profile, true));
 }
 
 MediaGalleriesPrivateAPIFactory::MediaGalleriesPrivateAPIFactory()