Implement CachedMetadata handling on MojoAsyncResourceHandler

content/common/url_loader.mojom

Index: content/common/url_loader.mojom
diff --git a/content/common/url_loader.mojom b/content/common/url_loader.mojom
index c0e63c873419c25b33fd0d8f0279e59503ee43e2..b801e0f6cee20f91d626f4bb24bf3a4bb18eef8c 100644
--- a/content/common/url_loader.mojom
+++ b/content/common/url_loader.mojom
@@ -48,6 +48,9 @@ interface URLLoaderClient {
   // instead.
   OnDataDownloaded(int64 data_length, int64 encoded_length);
 
+  // Called when cached metadata from a resource request is ready.
+  OnReceiveCachedMetadata(array<uint8> data);
+
   // Called when the transfer size is updated. This is only called if
   // |report_raw_headers| is set and |download_to_file| is unset in the request.
   // The transfer size is the length of the response (including both headers