Turn on component updater on chromeos, only for the pnacl component.

chrome/browser/component_updater/pnacl/pnacl_profile_observer.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/component_updater/pnacl/pnacl_profile_observer.h"
+
+#include "base/logging.h"
+#include "chrome/browser/component_updater/pnacl/pnacl_component_installer.h"
+#include "chrome/common/chrome_notification_types.h"
+#include "content/public/browser/notification_service.h"
+
+PnaclProfileObserver::PnaclProfileObserver(
+    PnaclComponentInstaller* installer) : pnacl_installer_(installer) {
+  // We only need to observe NOTIFICATION_LOGIN_USER_CHANGED for ChromeOS
+  // (and it's only defined for ChromeOS).
+#if defined(OS_CHROMEOS)
+  registrar_.Add(this,
+                 chrome::NOTIFICATION_LOGIN_USER_CHANGED,
+                 content::NotificationService::AllSources());
+#endif
+}
+
+PnaclProfileObserver::~PnaclProfileObserver() { }
+
+void PnaclProfileObserver::Observe(
+    int type,
+    const content::NotificationSource& source,
+    const content::NotificationDetails& details) {
+#if defined(OS_CHROMEOS)
+  if (type == chrome::NOTIFICATION_LOGIN_USER_CHANGED) {
+    pnacl_installer_->ReRegisterPnacl();
+    return;
+  }
+#endif

[cpu_(ooo_6.6-7.5), 2013/03/29 22:20:55]

the #endif should include the notreached, it seems.

[jvoung (off chromium), 2013/03/29 22:54:52]

Can the Observe() function get called in the non-OS_CHROMEOS case?  In the
non-OS_CHROMEOS case, nothing is .Add'ed to the "registrar_".

Maybe we don't need the NOTREACHED() at all?

+  NOTREACHED() << "Unexpected notification observed";
+}