Invoke callback from WebstoreInstaller when installation is fully complete

extensions/browser/extension_registry_observer.h

 // Copyright 2014 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_EXTENSION_REGISTRY_OBSERVER_H_
 #define EXTENSIONS_BROWSER_EXTENSION_REGISTRY_OBSERVER_H_
 
 #include "extensions/common/extension.h"
 
 namespace content {
@@ skipping 41 matching lines @@
   // TODO(tmdiep): We should stash the state of the previous extension version
   // somewhere and have observers retrieve it. |is_update|, |from_ephemeral|
   // and |old_name| can be removed when this is done.
   virtual void OnExtensionWillBeInstalled(
       content::BrowserContext* browser_context,
       const Extension* extension,
       bool is_update,
       bool from_ephemeral,
       const std::string& old_name) {}
 
-  // Called after an extension is uninstalled. The extension no longer exsit in
+  // Called when the installation of |extension| is complete. At this point the
+  // extension is tracked in one of the ExtensionRegistry sets, but is not
+  // necessarily enabled.

[asargent_no_longer_on_chrome, 2014/06/11 18:27:54]

Would it be helpful to pass the enabled/disabled state as an additional
parameter?

[tmdiep, 2014/06/11 22:56:18]

I think maybe not for this notification - it's for observers who want to know
when the entire installation process is complete. Observers that do things when
an extension is enabled listen for OnLoaded.

+  virtual void OnExtensionInstalled(content::BrowserContext* browser_context,
+                                    const Extension* extension) {}
+
+  // Called after an extension is uninstalled. The extension no longer exists in
   // any of the ExtensionRegistry sets (enabled, disabled, etc.).
   virtual void OnExtensionUninstalled(content::BrowserContext* browser_context,
                                       const Extension* extension) {}
 
   // Notifies observers that the observed object is going away.
   virtual void OnShutdown(ExtensionRegistry* registry) {}
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_BROWSER_EXTENSION_REGISTRY_OBSERVER_H_