Failing prefetch on net error

Previously, this code assumed that OnComplete would only be called after
OnReceiveResponse, but it can be called before that as well in the case
of a network failure.

Change-Id: I86072c1bd0e05521f2688ad1270e5b7246875676
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2602708Reviewed-by: Tarun Bansal <tbansal@chromium.org>
Commit-Queue: Ryan Sturm <ryansturm@chromium.org>
Cr-Commit-Position: refs/heads/master@{#839475}

chrome/browser/prefetch/search_prefetch/streaming_search_prefetch_url_loader.cc

@@ -272,7 +272,12 @@ void StreamingSearchPrefetchURLLoader::OnComplete(
 
   if (!forwarding_client_) {
     DCHECK(streaming_prefetch_request_);
-    streaming_prefetch_request_->MarkPrefetchAsComplete();
+    if (status.error_code == net::OK) {
+      streaming_prefetch_request_->MarkPrefetchAsComplete();
+    } else {
+      streaming_prefetch_request_->ErrorEncountered();
+      return;
+    }
   }
 
   status_ = status;