Add an extension bubble explaining which extensions are in dev mode.

chrome/browser/extensions/extension_prefs.cc

 // 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.
 
 #include "chrome/browser/extensions/extension_prefs.h"
 
 #include <iterator>
 
 #include "base/command_line.h"
 #include "base/prefs/pref_notifier.h"
@@ skipping 655 matching lines @@
 
 bool ExtensionPrefs::HasWipeoutBeenAcknowledged(
     const std::string& extension_id) {
   return ReadPrefAsBooleanAndReturn(extension_id, kPrefWipeoutAcknowledged);
 }
 
 void ExtensionPrefs::SetWipeoutAcknowledged(
     const std::string& extension_id,
     bool value) {
   UpdateExtensionPref(extension_id, kPrefWipeoutAcknowledged,
-                      Value::CreateBooleanValue(value));
+                      value ? Value::CreateBooleanValue(value) : NULL);
 }
 
 bool ExtensionPrefs::SetAlertSystemFirstRun() {
   if (prefs_->GetBoolean(prefs::kExtensionAlertsInitializedPref)) {
     return true;
   }
   prefs_->SetBoolean(prefs::kExtensionAlertsInitializedPref, true);
   return false;
 }
 
@@ skipping 1190 matching lines @@
     is_enabled = initial_state == Extension::ENABLED;
   }
 
   extension_pref_value_map_->RegisterExtension(extension_id, install_time,
                                                is_enabled);
   content_settings_store_->RegisterExtension(extension_id, install_time,
                                              is_enabled);
 }
 
 }  // namespace extensions