Teach EmbeddedWorkerInstance to create a process when it needs one.

content/browser/service_worker/service_worker_dispatcher_host.h

Index: content/browser/service_worker/service_worker_dispatcher_host.h
diff --git a/content/browser/service_worker/service_worker_dispatcher_host.h b/content/browser/service_worker/service_worker_dispatcher_host.h
index 473f239c9caacba90672709e3d87f04d10fc6f89..97b50bdc6f7066770209783a6292b0e85b005e84 100644
--- a/content/browser/service_worker/service_worker_dispatcher_host.h
+++ b/content/browser/service_worker/service_worker_dispatcher_host.h
@@ -31,11 +31,20 @@ class CONTENT_EXPORT ServiceWorkerDispatcherHost : public BrowserMessageFilter {
 
   void Init(ServiceWorkerContextWrapper* context_wrapper);
 
-  // BrowserIOMessageFilter implementation
+  // BrowserMessageFilter implementation
+  virtual void OnFilterAdded(IPC::Channel* channel) OVERRIDE;
   virtual void OnDestruct() const OVERRIDE;
   virtual bool OnMessageReceived(const IPC::Message& message,
                                  bool* message_was_ok) OVERRIDE;
 
+  // IPC::Sender implementation
+
+  // Send() queues the message until the underlying channel is ready.  This
+  // class assumes that Send() can only fail after that when the renderer
+  // process has terminated, at which point the whole instance will eventually
+  // be destroyed.
+  virtual bool Send(IPC::Message* message) OVERRIDE;
+
   void RegisterServiceWorkerHandle(scoped_ptr<ServiceWorkerHandle> handle);
 
  protected:
@@ -98,6 +107,9 @@ class CONTENT_EXPORT ServiceWorkerDispatcherHost : public BrowserMessageFilter {
 
   IDMap<ServiceWorkerHandle, IDMapOwnPointer> handles_;
 
+  bool channel_ready_;  // True after BrowserMessageFilter::channel_ != NULL.
+  ScopedVector<IPC::Message> pending_messages_;
+
   DISALLOW_COPY_AND_ASSIGN(ServiceWorkerDispatcherHost);
 };