chrome: Cleanup class/struct forward declarations

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 e0927284cd04e4746bb5d29f700d486dad2c2fc4..ba623c552a01f8981abd3fb41bf607696a8c594d 100644
--- a/chrome/browser/extensions/api/media_galleries/media_galleries_api.h
+++ b/chrome/browser/extensions/api/media_galleries/media_galleries_api.h
@@ -31,17 +31,10 @@ namespace MediaGalleries = extensions::api::media_galleries;
 
 namespace content {
 class BlobHandle;
-class WebContents;
-}
-
-namespace metadata {
-class SafeMediaMetadataParser;
 }
 
 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 BrowserContextKeyedAPI,