Add |SetImageDownloadLimit| to ImageFetcher to limit downloaded bytes

components/image_fetcher/core/image_fetcher.h

Index: components/image_fetcher/core/image_fetcher.h
diff --git a/components/image_fetcher/core/image_fetcher.h b/components/image_fetcher/core/image_fetcher.h
index e1b121b3e338ca9045343a6e92103fe1c9db71e6..0284aee9f250d2869c11ff9032366fd81f8dafa1 100644
--- a/components/image_fetcher/core/image_fetcher.h
+++ b/components/image_fetcher/core/image_fetcher.h
@@ -9,6 +9,7 @@
 
 #include "base/callback.h"
 #include "base/macros.h"
+#include "base/optional.h"
 #include "components/data_use_measurement/core/data_use_user_data.h"
 #include "components/image_fetcher/core/image_fetcher_delegate.h"
 #include "url/gurl.h"
@@ -44,6 +45,12 @@ class ImageFetcher {
   virtual void SetDataUseServiceName(
       DataUseServiceName data_use_service_name) = 0;
 
+  // Sets an upper limit for image downloads that is by default disabled.
+  // Setting |max_download_bytes| to a negative value will disable the limit.
+  // Already running downloads are immediately affected.
+  virtual void SetImageDownloadLimit(
+      base::Optional<int64_t> max_download_bytes) = 0;
+
   // Sets the desired size for images with multiple frames (like .ico files).
   // By default, the image fetcher choses smaller images. Override to choose a
   // frame with a size as close as possible to |size| (trying to take one in