Teach EmbeddedWorkerInstance to create a process when it needs one.

content/browser/service_worker/service_worker_dispatcher_host.cc

Index: content/browser/service_worker/service_worker_dispatcher_host.cc
diff --git a/content/browser/service_worker/service_worker_dispatcher_host.cc b/content/browser/service_worker/service_worker_dispatcher_host.cc
index 562fc9571cafa89b4f368e976f77d64af40dc6fe..ec6a8396914b9b9dfc235d4c2973855458566018 100644
--- a/content/browser/service_worker/service_worker_dispatcher_host.cc
+++ b/content/browser/service_worker/service_worker_dispatcher_host.cc
@@ -44,7 +44,9 @@ ServiceWorkerDispatcherHost::ServiceWorkerDispatcherHost(
     : BrowserMessageFilter(kFilteredMessageClasses,
                            arraysize(kFilteredMessageClasses)),
       render_process_id_(render_process_id),
-      message_port_message_filter_(message_port_message_filter) {}
+      message_port_message_filter_(message_port_message_filter),
+      channel_ready_(false) {
+}
 
 ServiceWorkerDispatcherHost::~ServiceWorkerDispatcherHost() {
   if (context_) {
@@ -68,6 +70,16 @@ void ServiceWorkerDispatcherHost::Init(
       render_process_id_, this);
 }
 
+void ServiceWorkerDispatcherHost::OnFilterAdded(IPC::Channel* channel) {
+  BrowserMessageFilter::OnFilterAdded(channel);
+  channel_ready_ = true;
+  std::vector<IPC::Message*> messages;
+  pending_messages_.release(&messages);
+  for (size_t i = 0; i < messages.size(); ++i) {
+    BrowserMessageFilter::Send(messages[i]);
+  }

[kinuko, 2014/04/25 13:46:35]

Thanks for fixing this part... (should all message filters that inherit from
BrowserMessageFilter do something like this?)

[Jeffrey Yasskin, 2014/04/26 03:52:19]

According to jam@, "historically, message filters have been used to respond to
IPCs from the renderer", and after an IPC is received, the channel is guaranteed
to be ready. I think this should be documented better, and perhaps
BrowserMessageFilter should DCHECK its Send() result instead of passing it
through, but it's not clear that "all message filters" are going to run into
this problem.

+}
+
 void ServiceWorkerDispatcherHost::OnDestruct() const {
   BrowserThread::DeleteOnIOThread::Destruct(this);
 }
@@ -116,6 +128,17 @@ bool ServiceWorkerDispatcherHost::OnMessageReceived(
   return handled;
 }
 
+bool ServiceWorkerDispatcherHost::Send(IPC::Message* message) {
+  if (channel_ready_) {
+    BrowserMessageFilter::Send(message);
+    // Don't bother passing through Send()'s result: it's not reliable.
+    return true;
+  }
+
+  pending_messages_.push_back(message);
+  return true;
+}
+
 void ServiceWorkerDispatcherHost::RegisterServiceWorkerHandle(
     scoped_ptr<ServiceWorkerHandle> handle) {
   int handle_id = handle->handle_id();