Add ref count to service workers for extension API.

content/browser/service_worker/embedded_worker_instance.cc

Index: content/browser/service_worker/embedded_worker_instance.cc
diff --git a/content/browser/service_worker/embedded_worker_instance.cc b/content/browser/service_worker/embedded_worker_instance.cc
index a0c48cd25fcf2d7e7dcf2b6d0c9d7fa7a9a7c78b..d0db28120bb3ee108610b050756446478b8f6ace 100644
--- a/content/browser/service_worker/embedded_worker_instance.cc
+++ b/content/browser/service_worker/embedded_worker_instance.cc
@@ -7,6 +7,7 @@
 #include <utility>
 
 #include "base/bind_helpers.h"
+#include "base/logging.h"
 #include "base/macros.h"
 #include "base/memory/ptr_util.h"
 #include "base/metrics/histogram_macros.h"
@@ -482,6 +483,10 @@ void EmbeddedWorkerInstance::StopIfIdle() {
       devtools_proxy_->NotifyWorkerStopIgnored();
     return;
   }
+  if (external_ref_count_ > 0) {
+    LOG(WARNING) << "Skipped StopIfIdle due to external_ref_count_";
+    return;
+  }
   Stop();
 }
 
@@ -531,6 +536,7 @@ EmbeddedWorkerInstance::EmbeddedWorkerInstance(
       thread_id_(kInvalidEmbeddedWorkerThreadId),
       devtools_attached_(false),
       network_accessed_for_script_(false),
+      external_ref_count_(0),
       weak_factory_(this) {}
 
 void EmbeddedWorkerInstance::OnProcessAllocated(
@@ -726,6 +732,15 @@ void EmbeddedWorkerInstance::Detach() {
   OnDetached();
 }
 
+void EmbeddedWorkerInstance::IncrementRefCount() {
+  ++external_ref_count_;
+}
+
+void EmbeddedWorkerInstance::DecrementRefCount() {
+  DCHECK(external_ref_count_ > 0);
+  --external_ref_count_;
+}
+
 base::WeakPtr<EmbeddedWorkerInstance> EmbeddedWorkerInstance::AsWeakPtr() {
   return weak_factory_.GetWeakPtr();
 }