[BlobStorage] Better net error reporting for pre-broken blobs

storage/browser/blob/blob_url_request_job.cc

Index: storage/browser/blob/blob_url_request_job.cc
diff --git a/storage/browser/blob/blob_url_request_job.cc b/storage/browser/blob/blob_url_request_job.cc
index 64c17a9869497b5baca6a46c6b49829ac3283aec..8d7aaea7c2dae0f35deb53893f90d7013bda499b 100644
--- a/storage/browser/blob/blob_url_request_job.cc
+++ b/storage/browser/blob/blob_url_request_job.cc
@@ -162,6 +162,10 @@ void BlobURLRequestJob::DidStart() {
     NotifyFailure(net::ERR_FILE_NOT_FOUND);
     return;
   }
+  if (blob_reader_->net_error()) {
+    NotifyFailure(blob_reader_->net_error());
+    return;
+  }
 
   TRACE_EVENT_ASYNC_BEGIN1("Blob", "BlobRequest::CountSize", this, "uuid",
                            blob_handle_->uuid());