Install and launch kiosk app from cached crx file at start up.

chrome/browser/chromeos/extensions/external_cache.cc

 // Copyright (c) 2013 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/chromeos/extensions/external_cache.h"
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/callback.h"
 #include "base/file_util.h"
@@ skipping 135 matching lines @@
     const std::string& id,
     extensions::ExtensionDownloaderDelegate::Error error,
     const extensions::ExtensionDownloaderDelegate::PingResult& ping_result,
     const std::set<int>& request_ids) {
   if (error == NO_UPDATE_AVAILABLE) {
     if (!cached_extensions_->HasKey(id)) {
       LOG(ERROR) << "ExternalCache extension " << id
                  << " not found on update server";
       delegate_->OnExtensionDownloadFailed(id, error);
     } else {
+      // No version update for an already cached extension.
       delegate_->OnExtensionLoadedInCache(id);
     }
   } else {
     LOG(ERROR) << "ExternalCache failed to download extension " << id
                << ", error " << error;
     delegate_->OnExtensionDownloadFailed(id, error);
   }
 }
 
 void ExternalCache::OnExtensionDownloadFinished(
@@ skipping 153 matching lines @@
     delegate_->OnExtensionLoadedInCache(id);
   UpdateExtensionLoader();
 }
 
 std::string ExternalCache::Delegate::GetInstalledExtensionVersion(
     const std::string& id) {
   return std::string();
 }
 
 }  // namespace chromeos