Remove NOTIFICATION_EXTENSION_ENABLED.

extensions/browser/events/lazy_event_dispatch_util.h

+// Copyright 2017 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 EXTENSIONS_BROWSER_EVENTS_LAZY_EVENT_DISPATCH_UTIL_H_
+#define EXTENSIONS_BROWSER_EVENTS_LAZY_EVENT_DISPATCH_UTIL_H_
+
+#include "base/observer_list.h"
+#include "base/scoped_observer.h"
+#include "extensions/browser/extension_registry_observer.h"
+#include "extensions/browser/uninstall_reason.h"
+
+namespace base {
+class Version;
+}
+
+namespace extensions {
+
+class LazyEventDispatchUtil : public ExtensionRegistryObserver {

[Devlin, 2017/06/05 15:38:38]

class comments.  In particular, it might be nice to note how this tracks
updates/installs/etc (with pref entries)

[lazyboy, 2017/06/05 21:54:01]

Done.

+ public:
+  // Helps observer with events for lazy event dispatching.
+  class Observer {
+   public:
+    // Called when an extension is loaded after installation, for one of the
+    // following scenarios:
+    //   1. New extension is installed.
+    //   2. An extension is updated and loaded.
+    //   3. An extension is enabled after it was disabled during an update.
+    virtual void OnExtensionInstalledAndLoaded(
+        content::BrowserContext* browser_context,
+        const Extension* extension,
+        const base::Version& old_version) {}
+  };
+
+  explicit LazyEventDispatchUtil(content::BrowserContext* browser_context);
+  ~LazyEventDispatchUtil() override;
+
+  void AddObserver(Observer* observer);
+  void RemoveObserver(Observer* observer);
+
+  // ExtensionRegistryObserver:
+  void OnExtensionLoaded(content::BrowserContext* browser_context,
+                         const Extension* extension) override;
+  void OnExtensionWillBeInstalled(content::BrowserContext* browser_context,
+                                  const Extension* extension,
+                                  bool is_update,
+                                  const std::string& old_name) override;
+  void OnExtensionUninstalled(content::BrowserContext* browser_context,
+                              const Extension* extension,
+                              UninstallReason reason) override;
+
+ private:
+  bool ReadPendingOnInstallInfoFromPref(const ExtensionId& extension_id,
+                                        base::Version* previous_version);
+  void RemovePendingOnInstallInfoFromPref(const ExtensionId& extension_id);
+  void StorePendingOnInstallInfoToPref(const Extension* extension);
+
+  content::BrowserContext* browser_context_;
+  base::ObserverList<Observer> observers_;
+  ScopedObserver<ExtensionRegistry, ExtensionRegistryObserver>
+      extension_registry_observer_;
+
+  DISALLOW_COPY_AND_ASSIGN(LazyEventDispatchUtil);
+};
+
+}  // namespace extensions
+
+#endif  // EXTENSIONS_BROWSER_EVENTS_LAZY_EVENT_DISPATCH_UTIL_H_