Check remote connection in ServiceWorkerContainerHost::CountFeature()

This is a workaround to handle a situation where `container_` is
disconnected when CountFeature() is called. Ideally `container_`
should not be disconnected during the lifetime of
ServiceWorkerContainerHost. This CL is a mitigation until we figure
out the root cause.

Bug: 1136843
Change-Id: I666624b2142d538b60957dd594cb2c3557e42a91
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2522719Reviewed-by: Makoto Shimazu <shimazu@chromium.org>
Commit-Queue: Kenichi Ishibashi <bashi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#825245}

content/browser/service_worker/service_worker_container_host.cc

@@ -525,6 +525,12 @@ void ServiceWorkerContainerHost::CountFeature(
   if (!is_execution_ready())
     return;
 
+  // `container_` shouldn't be disconnected during the lifetime of `this` but
+  // there seems a situation where `container_` is disconnected.
+  // TODO(crbug.com/1136843): Figure out the cause and remove this check.
+  if (!container_.is_connected())
+    return;
+
   container_->CountFeature(feature);
 }