Use mime type for image extension

components/image_fetcher/image_fetcher_impl.h

Index: components/image_fetcher/image_fetcher_impl.h
diff --git a/components/image_fetcher/image_fetcher_impl.h b/components/image_fetcher/image_fetcher_impl.h
index 05856e8b8fd01335667a85ecc11839ac64af8f13..fc60098ab90af661ec80614d48d3fbe40c6f40ef 100644
--- a/components/image_fetcher/image_fetcher_impl.h
+++ b/components/image_fetcher/image_fetcher_impl.h
@@ -76,7 +76,9 @@ class ImageFetcherImpl : public image_fetcher::ImageFetcher {
 
   // Processes image URL fetched events. This is the continuation method used
   // for creating callbacks that are passed to the ImageDataFetcher.
-  void OnImageURLFetched(const GURL& image_url, const std::string& image_data);
+  void OnImageURLFetched(const GURL& image_url,
+                         const std::string& image_data,
+                         const std::string& mime_type);
 
   // Processes image decoded events. This is the continuation method used for
   // creating callbacks that are passed to the ImageDecoder.