Add a non-blocking "OneShotEvent" class

chrome/browser/extensions/extension_service.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_EXTENSIONS_EXTENSION_SERVICE_H_
 #define CHROME_BROWSER_EXTENSIONS_EXTENSION_SERVICE_H_
 
 #include <list>
 #include <map>
 #include <set>
@@ skipping 20 matching lines @@
 #include "chrome/browser/extensions/menu_manager.h"
 #include "chrome/browser/extensions/pending_extension_manager.h"
 #include "chrome/browser/extensions/process_map.h"
 #include "chrome/browser/extensions/update_observer.h"
 #include "chrome/common/extensions/extension.h"
 #include "chrome/common/extensions/extension_constants.h"
 #include "chrome/common/extensions/extension_set.h"
 #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"
 
 class CommandLine;
 class ExtensionErrorUI;
 class ExtensionSyncData;
 class ExtensionToolbarModel;
 class GURL;
 class Profile;
@@ skipping 73 matching lines @@
   virtual void AddComponentExtension(
       const extensions::Extension* extension) = 0;
 
   virtual void UnloadExtension(
       const std::string& extension_id,
       extension_misc::UnloadedExtensionReason reason) = 0;
 
   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.
 class ExtensionService
     : public ExtensionServiceInterface,
       public extensions::ExternalProviderInterface::VisitorInterface,
       public content::NotificationObserver,
       public extensions::Blacklist::Observer {
  public:
   // The name of the directory inside the profile where extensions are
@@ skipping 366 matching lines @@
   Profile* profile();
 
   // TODO(skerner): Change to const ExtensionPrefs& extension_prefs() const,
   // ExtensionPrefs* mutable_extension_prefs().
   extensions::ExtensionPrefs* extension_prefs();
 
   extensions::SettingsFrontend* settings_frontend();
 
   extensions::ContentSettingsStore* GetContentSettingsStore();
 
-  // Whether the extension service is ready.
-  virtual bool is_ready() OVERRIDE;
-
   virtual base::SequencedTaskRunner* GetFileTaskRunner() OVERRIDE;
 
   extensions::ComponentLoader* component_loader() {
     return component_loader_.get();
   }
 
   // Note that this may return NULL if autoupdate is not turned on.
   extensions::ExtensionUpdater* updater();
 
   ExtensionToolbarModel* toolbar_model() { return &toolbar_model_; }
@@ skipping 359 matching lines @@
   // Whether to notify users when they attempt to install an extension.
   bool show_extensions_prompts_;
 
   // Whether to delay installing of extension updates until the extension is
   // idle.
   bool install_updates_when_idle_;
 
   // 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_;
 
   // The model that tracks extensions with BrowserAction buttons.
   ExtensionToolbarModel toolbar_model_;
 
   // Map unloaded extensions' ids to their paths. When a temporarily loaded
   // extension is unloaded, we lose the information about it and don't have
   // any in the extension preferences file.
   typedef std::map<std::string, base::FilePath> UnloadedExtensionPathMap;
@@ skipping 81 matching lines @@
   ObserverList<extensions::UpdateObserver, true> update_observers_;
 
   FRIEND_TEST_ALL_PREFIXES(ExtensionServiceTest,
                            InstallAppsWithUnlimtedStorage);
   FRIEND_TEST_ALL_PREFIXES(ExtensionServiceTest,
                            InstallAppsAndCheckStorageProtection);
   DISALLOW_COPY_AND_ASSIGN(ExtensionService);
 };
 
 #endif  // CHROME_BROWSER_EXTENSIONS_EXTENSION_SERVICE_H_