Remove InstallTracker's extension installed, uninstalled observers.

chrome/browser/extensions/install_tracker.h

Index: chrome/browser/extensions/install_tracker.h
diff --git a/chrome/browser/extensions/install_tracker.h b/chrome/browser/extensions/install_tracker.h
index 637dd985d52e1e37114a9aed059ebab60f01bb72..9624000f2fe7523fbb402fcfaf7b7db257e1c57d 100644
--- a/chrome/browser/extensions/install_tracker.h
+++ b/chrome/browser/extensions/install_tracker.h
@@ -7,12 +7,10 @@
 
 #include "base/observer_list.h"
 #include "base/prefs/pref_change_registrar.h"
-#include "base/scoped_observer.h"
 #include "chrome/browser/extensions/install_observer.h"
 #include "components/keyed_service/core/keyed_service.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
-#include "extensions/browser/extension_registry_observer.h"
 
 class Profile;
 
@@ -23,11 +21,9 @@ class BrowserContext;
 namespace extensions {
 
 class ExtensionPrefs;
-class ExtensionRegistry;
 
 class InstallTracker : public KeyedService,
-                       public content::NotificationObserver,
-                       public ExtensionRegistryObserver {
+                       public content::NotificationObserver {
  public:
   InstallTracker(Profile* profile,
                  extensions::ExtensionPrefs* prefs);
@@ -47,6 +43,9 @@ class InstallTracker : public KeyedService,
   void OnFinishCrxInstall(const std::string& extension_id, bool success);
   void OnInstallFailure(const std::string& extension_id);
 
+  // NOTE(limasdf): For extension [un]load and [un]installed, use
+  //                ExtensionRegistryObserver.
+
   // Overriddes for KeyedService.
   virtual void Shutdown() OVERRIDE;
 
@@ -58,21 +57,10 @@ class InstallTracker : public KeyedService,
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) OVERRIDE;
 
-  // ExtensionRegistryObserver implementation.
-  virtual void OnExtensionWillBeInstalled(
-      content::BrowserContext* browser_context,
-      const Extension* extension,
-      bool is_update,
-      bool from_ephemeral,
-      const std::string& old_name) OVERRIDE;
-
   ObserverList<InstallObserver> observers_;
   content::NotificationRegistrar registrar_;
   PrefChangeRegistrar pref_change_registrar_;
 
-  ScopedObserver<ExtensionRegistry, ExtensionRegistryObserver>
-      extension_registry_observer_;
-
   DISALLOW_COPY_AND_ASSIGN(InstallTracker);
 };