Add a non-blocking "OneShotEvent" class

chrome/browser/extensions/extension_system.cc

Index: chrome/browser/extensions/extension_system.cc
diff --git a/chrome/browser/extensions/extension_system.cc b/chrome/browser/extensions/extension_system.cc
index 0a141447866847d3153f84ec583dde0392dae13f..37b4c857983cffecdf5391b4a08e958afc43aada 100644
--- a/chrome/browser/extensions/extension_system.cc
+++ b/chrome/browser/extensions/extension_system.cc
@@ -151,6 +151,8 @@ void ExtensionSystemImpl::Shared::Init(bool extensions_enabled) {
       blacklist_.get(),
       autoupdate_enabled,
       extensions_enabled));
+  extension_service_->ready().RunAfter(
+      FROM_HERE, base::Bind(&AsyncEvent::MarkHappened, ready_.AsWeakPtr()));

[Matt Perry, 2013/05/15 21:08:54]

I think it will get confusing to have 2 "ready" signals for extensions. All of
extensions should become ready at the same time. I don't have a strong opinion
which class should hold the |ready| object, but only one of them should.

[Jeffrey Yasskin, 2013/05/15 22:46:50]

Ok, I've moved them into ExtensionSystem. They need to be there instead of
ExtensionService because many users want to schedule something to happen after
'ready' when the ExtensionService might not have been created yet.

 
   // These services must be registered before the ExtensionService tries to
   // load any extensions.
@@ -436,6 +438,10 @@ Blacklist* ExtensionSystemImpl::blacklist() {
   return shared_->blacklist();
 }
 
+const AsyncEvent& ExtensionSystemImpl::ready() const {
+  return shared_->ready();
+}
+
 void ExtensionSystemImpl::RegisterExtensionWithRequestContexts(
     const Extension* extension) {
   base::Time install_time;