Add a non-blocking "OneShotEvent" class

chrome/browser/extensions/extension_service.h

Index: chrome/browser/extensions/extension_service.h
diff --git a/chrome/browser/extensions/extension_service.h b/chrome/browser/extensions/extension_service.h
index 70b1a5fd094598b098f793d915f266e226ea444b..11ea30890b01f581cea991a040844d7a440f2a92 100644
--- a/chrome/browser/extensions/extension_service.h
+++ b/chrome/browser/extensions/extension_service.h
@@ -38,6 +38,7 @@
 #include "chrome/common/extensions/manifest.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
+#include "extensions/common/async_event.h"
 #include "sync/api/string_ordinal.h"
 #include "sync/api/sync_change.h"
 #include "sync/api/syncable_service.h"
@@ -131,10 +132,17 @@ class ExtensionServiceInterface : public syncer::SyncableService {
   virtual void SyncExtensionChangeIfNeeded(
       const extensions::Extension& extension) = 0;
 
-  virtual bool is_ready() = 0;
+  // Whether the extension service is ready.
+  bool is_ready() const { return ready_.has_happened(); }

[Yoyo Zhou, 2013/05/15 22:38:41]

Arguably, the point of AsyncEvent is to not have to write different code paths
for ready/unready, so is it necessary to have an "is_ready" at all?

[Matt Perry, 2013/05/15 22:41:54]

I was actually leaning the other way - that maybe the fact that |ready| is an
AsyncEvent is an implementation detail, and we should really only expose IsReady
and RunWhenReady APIs.

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

We need is_ready for backward-compatibility with existing ExtensionService code,
and I suspect it'll keep being useful for other migrations. You're right that
any use of it in client code is likely unwise. I'll add a comment.

+  const extensions::AsyncEvent& ready() { return ready_; }

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

I can see why you did this, but as an interface, this class shouldn't have an
implemented methods.

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

Done.

 
   // Returns task runner for crx installation file I/O operations.
   virtual base::SequencedTaskRunner* GetFileTaskRunner() = 0;
+
+ protected:
+  // Record that Init() has been called, and chrome::EXTENSIONS_READY
+  // has fired.
+  extensions::AsyncEvent ready_;
 };
 
 // Manages installed and running Chromium extensions.
@@ -521,9 +529,6 @@ class ExtensionService
 
   extensions::ContentSettingsStore* GetContentSettingsStore();
 
-  // Whether the extension service is ready.
-  virtual bool is_ready() OVERRIDE;
-
   virtual base::SequencedTaskRunner* GetFileTaskRunner() OVERRIDE;
 
   extensions::ComponentLoader* component_loader() {
@@ -903,10 +908,6 @@ class ExtensionService
   // Used by dispatchers to limit API quota for individual extensions.
   ExtensionsQuotaService quota_service_;
 
-  // Record that Init() has been called, and chrome::EXTENSIONS_READY
-  // has fired.
-  bool ready_;
-
   // Our extension updater, if updates are turned on.
   scoped_ptr<extensions::ExtensionUpdater> updater_;