Use mime type for image extension

components/image_fetcher/image_fetcher_impl.cc

Index: components/image_fetcher/image_fetcher_impl.cc
diff --git a/components/image_fetcher/image_fetcher_impl.cc b/components/image_fetcher/image_fetcher_impl.cc
index d260b2cdd2a09436a2f2c840416dc3c60d05b4b0..e417e3c79f79ba637860762267887d4bb0c8a729 100644
--- a/components/image_fetcher/image_fetcher_impl.cc
+++ b/components/image_fetcher/image_fetcher_impl.cc
@@ -63,7 +63,8 @@ void ImageFetcherImpl::StartOrQueueNetworkRequest(
 }
 
 void ImageFetcherImpl::OnImageURLFetched(const GURL& image_url,
-                                         const std::string& image_data) {
+                                         const std::string& image_data,
+                                         const RequestMetadata& metadata) {
   // Inform the ImageFetcherDelegate.
   if (delegate_) {
     auto it = pending_net_requests_.find(image_url);