ServiceWorker: Add CHECK to EmbeddedWorkerRegistry for debug

content/browser/service_worker/embedded_worker_registry.cc

Index: content/browser/service_worker/embedded_worker_registry.cc
diff --git a/content/browser/service_worker/embedded_worker_registry.cc b/content/browser/service_worker/embedded_worker_registry.cc
index 51d3c2c5ca2d368f5c1dbb27e3277fdad58fe1cf..1b75f9407f63cec6135191da510dd9a6c5908fab 100644
--- a/content/browser/service_worker/embedded_worker_registry.cc
+++ b/content/browser/service_worker/embedded_worker_registry.cc
@@ -229,6 +229,10 @@ bool EmbeddedWorkerRegistry::CanHandle(int embedded_worker_id) const {
 
 MessagePortMessageFilter*
 EmbeddedWorkerRegistry::MessagePortMessageFilterForProcess(int process_id) {
+  // TODO(nhiroki): Change this to DCHECK after https://crbug.com/648477 is
+  // fixed.
+  CHECK(
+      base::ContainsKey(process_message_port_message_filter_map_, process_id));
   return process_message_port_message_filter_map_[process_id];
 }