Skip notifying ControlleeRemoved if the client has already been removed

There's a bug that AddControllee and RemoveControllee don't match. This
is a workaround to avoid notifying the mismatching OnControlleeRemoved.

Bug: 1021718, 1015692, 1088353
Change-Id: I901de49164a650409275e43d51440ae58b5286be
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2493961
Auto-Submit: Makoto Shimazu <shimazu@chromium.org>
Commit-Queue: Kenichi Ishibashi <bashi@chromium.org>
Reviewed-by: Kenichi Ishibashi <bashi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#820158}

content/browser/service_worker/service_worker_version.cc

@@ -796,7 +796,11 @@ void ServiceWorkerVersion::AddControllee(
 
 void ServiceWorkerVersion::RemoveControllee(const std::string& client_uuid) {
   DCHECK_CURRENTLY_ON(ServiceWorkerContext::GetCoreThreadId());
-  DCHECK(base::Contains(controllee_map_, client_uuid));
+  // TODO(crbug.com/1015692): Remove this once RemoveControllee() matches with
+  // AddControllee().
+  if (!base::Contains(controllee_map_, client_uuid))
+    return;
+
   controllee_map_.erase(client_uuid);
 
   embedded_worker_->UpdateForegroundPriority();