Add recommended extension installation support

chrome/browser/extensions/extension_service.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/extensions/extension_service.h"
 
 #include <algorithm>
 #include <iterator>
 #include <set>
 
@@ skipping 669 matching lines @@
     const base::Closure& deletion_done_callback,
     base::string16* error) {
   CHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 
   scoped_refptr<const Extension> extension =
       GetInstalledExtension(transient_extension_id);
 
   // Callers should not send us nonexistent extensions.
   CHECK(extension.get());
 
+  ManagementPolicy* by_policy = system_->management_policy();
   // Policy change which triggers an uninstall will always set
   // |external_uninstall| to true so this is the only way to uninstall
   // managed extensions.
   // Shared modules being uninstalled will also set |external_uninstall| to true
   // so that we can guarantee users don't uninstall a shared module.
   // (crbug.com/273300)
   // TODO(rdevlin.cronin): This is probably not right. We should do something
   // else, like include an enum IS_INTERNAL_UNINSTALL or IS_USER_UNINSTALL so
   // we don't do this.
   bool external_uninstall =
       (reason == extensions::UNINSTALL_REASON_INTERNAL_MANAGEMENT) ||
       (reason == extensions::UNINSTALL_REASON_ORPHANED_EXTERNAL_EXTENSION) ||
       (reason == extensions::UNINSTALL_REASON_ORPHANED_SHARED_MODULE) ||
       (reason == extensions::UNINSTALL_REASON_SYNC &&
            extension->was_installed_by_custodian());
   if (!external_uninstall &&
-      !system_->management_policy()->UserMayModifySettings(
-        extension.get(), error)) {
+      (!by_policy->UserMayModifySettings(extension.get(), error) ||
+       by_policy->MustRemainInstalled(extension.get(), error))) {
     content::NotificationService::current()->Notify(
         extensions::NOTIFICATION_EXTENSION_UNINSTALL_NOT_ALLOWED,
         content::Source<Profile>(profile_),
         content::Details<const Extension>(extension.get()));
     return false;
   }
 
   syncer::SyncChange sync_change;
   if (extension_sync_service_) {
      sync_change = extension_sync_service_->PrepareToSyncUninstallExtension(
@@ skipping 1632 matching lines @@
 }
 
 void ExtensionService::OnProfileDestructionStarted() {
   ExtensionIdSet ids_to_unload = registry_->enabled_extensions().GetIDs();
   for (ExtensionIdSet::iterator it = ids_to_unload.begin();
        it != ids_to_unload.end();
        ++it) {
     UnloadExtension(*it, UnloadedExtensionInfo::REASON_PROFILE_SHUTDOWN);
   }
 }