Add NOTIFICATION_EXTENSION_REMOVED for Extensions removed from ExtensionService.

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 15645875447357ba74104449b8a584ce725fe9b2..d12903b25a0214a8dd61a441f76b7b53d1918cf0 100644
--- a/chrome/browser/extensions/extension_service.h
+++ b/chrome/browser/extensions/extension_service.h
@@ -15,6 +15,7 @@
 #include "base/gtest_prod_util.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/weak_ptr.h"
+#include "base/observer_list.h"
 #include "base/prefs/pref_change_registrar.h"
 #include "base/strings/string16.h"
 #include "chrome/browser/extensions/app_sync_bundle.h"
@@ -135,6 +136,16 @@ class ExtensionService
       public content::NotificationObserver,
       public extensions::Blacklist::Observer {
  public:
+  class DisabledExtensionObserver {
+   public:
+    // Called when an extension is removed from the disabled extensions list.
+    // |was_enabled| is true if it was enabled, false if it was blacklisted
+    // or uninstalled.
+    virtual void OnDisabledExtensionRemoved(

[Matt Perry, 2013/08/01 00:37:33]

This seems oddly specific. I think it should be split into 2 notifications:
- EXTENSION_ENABLED (or _LOADED would work, too)
- EXTENSION_DELETED
(or Observer methods if you prefer that. But then I would add the methods to
InstallObserver
https://code.google.com/p/chromium/codesearch#chromium/src/chrome/browser/ext...
)

[Yoyo Zhou, 2013/08/01 00:46:40]

To be clear, there are paths which result in an Extension being destroyed
without it being enabled or uninstalled (I think upgrade might be one of them).
We're actually interested in knowing whenever it's not disabled anymore. For
that we could bring back the EXTENSION_UNLOADED_DISABLED notification, but in
general I thought we were moving away from notifications.

So would you prefer this to be two methods, OnDisabledExtensionEnabled and
OnDisabledExtensionDeleted?

InstallObserver doesn't really look like a good fit. Too many pure virtual
methods we don't care about.

+        const extensions::Extension* extension,
+        bool was_enabled) = 0;
+  };
+
   // If auto-updates are turned on, default to running every 5 hours.
   static const int kDefaultUpdateFrequencySeconds = 60 * 60 * 5;
 
@@ -685,6 +696,10 @@ class ExtensionService
     install_updates_when_idle_ = value;
   }
 
+  // Adds/Removes disabled extension observers.
+  void AddDisabledExtensionObserver(DisabledExtensionObserver* observer);
+  void RemoveDisabledExtensionObserver(DisabledExtensionObserver* observer);
+
   // Adds/Removes update observers.
   void AddUpdateObserver(extensions::UpdateObserver* observer);
   void RemoveUpdateObserver(extensions::UpdateObserver* observer);
@@ -949,6 +964,7 @@ class ExtensionService
       extension_action_storage_manager_;
 #endif
 
+  ObserverList<DisabledExtensionObserver, true> disabled_extension_observers_;
   ObserverList<extensions::UpdateObserver, true> update_observers_;
 
   // Run()ning tells sync to try and start soon, because syncable changes