Disable extensions besides externally installed ones and themes.

chrome/browser/extensions/extensions_service.cc

Index: chrome/browser/extensions/extensions_service.cc
diff --git a/chrome/browser/extensions/extensions_service.cc b/chrome/browser/extensions/extensions_service.cc
index a9f81cab2d77570808c546f1ab7c842405528f43..7960664fbe73bc1307685d2810662330f3db79ec 100644
--- a/chrome/browser/extensions/extensions_service.cc
+++ b/chrome/browser/extensions/extensions_service.cc
@@ -216,22 +216,26 @@ ExtensionsService::ExtensionsService(Profile* profile,
     : extension_prefs_(new ExtensionPrefs(profile->GetPrefs())),
       backend_loop_(backend_loop),
       install_directory_(profile->GetPath().AppendASCII(kInstallDirectoryName)),
-      extensions_enabled_(
-          CommandLine::ForCurrentProcess()->
-          HasSwitch(switches::kEnableExtensions)),
+      extensions_enabled_(false),
       show_extensions_prompts_(true),
       ready_(false) {
   // We pass ownership of this object to the Backend.
   DictionaryValue* extensions = extension_prefs_->CopyCurrentExtensions();
   backend_ = new ExtensionsServiceBackend(
           install_directory_, g_browser_process->resource_dispatcher_host(),
-          frontend_loop, extensions);
+          frontend_loop, extensions, extensions_enabled());
 }
 
 ExtensionsService::~ExtensionsService() {
   UnloadAllExtensions();
 }
 
+void ExtensionsService::SetExtensionsEnabled(bool enabled) {
+  extensions_enabled_ = true;
+  backend_loop_->PostTask(FROM_HERE, NewRunnableMethod(backend_.get(),
+    &ExtensionsServiceBackend::set_extensions_enabled, enabled));
+}
+
 void ExtensionsService::Init() {
   DCHECK(extensions_.size() == 0);
 
@@ -354,13 +358,14 @@ void ExtensionsService::OnLoadedInstalledExtensions() {
 void ExtensionsService::OnExtensionsLoaded(ExtensionList* new_extensions) {
   scoped_ptr<ExtensionList> cleanup(new_extensions);
 
-  // Filter out any extensions we don't want to enable. Themes are always
-  // enabled, but other extensions are only loaded if --enable-extensions is
-  // present.
+  // Filter out any extensions that shouldn't be loaded. Themes are always
+  // loaded, but other extensions are only loaded if the extensions system is
+  // enabled.
   ExtensionList enabled_extensions;
   for (ExtensionList::iterator iter = new_extensions->begin();
        iter != new_extensions->end(); ++iter) {
-    if (extensions_enabled() || (*iter)->IsTheme()) {
+    if (extensions_enabled() || (*iter)->IsTheme() ||
+        (*iter)->location() == Extension::EXTERNAL_REGISTRY) {
       Extension* old = GetExtensionById((*iter)->id());
       if (old) {
         if ((*iter)->version()->CompareTo(*(old->version())) > 0) {
@@ -451,12 +456,14 @@ void ExtensionsService::SetProviderForTesting(
 
 ExtensionsServiceBackend::ExtensionsServiceBackend(
     const FilePath& install_directory, ResourceDispatcherHost* rdh,
-    MessageLoop* frontend_loop, DictionaryValue* extension_prefs)
+    MessageLoop* frontend_loop, DictionaryValue* extension_prefs,
+    bool extensions_enabled)
         : frontend_(NULL),
           install_directory_(install_directory),
           resource_dispatcher_host_(rdh),
           alert_on_error_(false),
-          frontend_loop_(frontend_loop) {
+          frontend_loop_(frontend_loop),
+          extensions_enabled_(false) {
   external_extension_providers_[Extension::EXTERNAL_PREF] =
       linked_ptr<ExternalExtensionProvider>(
           new ExternalPrefExtensionProvider(extension_prefs));
@@ -956,28 +963,22 @@ void ExtensionsServiceBackend::OnExtensionUnpacked(
     return;
   }
 
-  if (!frontend_->extensions_enabled() && !extension.IsTheme()) {
-#if defined(OS_WIN)
-    if (frontend_->show_extensions_prompts()) {
-      win_util::MessageBox(GetForegroundWindow(),
-          L"Extensions are not enabled. Add --enable-extensions to the "
-          L"command-line to enable extensions.\n\n"
-          L"This is a temporary message and it will be removed when extensions "
-          L"UI is finalized.",
-          l10n_util::GetString(IDS_PRODUCT_NAME).c_str(), MB_OK);
-    }
-#endif
+  Extension::Location location = Extension::INTERNAL;
+  LookupExternalExtension(extension.id(), NULL, &location);
+
+  // We currently only allow themes and registry-installed extensions to be
+  // installed.
+  if (!extensions_enabled_ &&
+      !extension.IsTheme() &&
+      location != Extension::EXTERNAL_REGISTRY) {
     ReportExtensionInstallError(extension_path,
-        "Extensions are not enabled.");
+                                "Extensions are not enabled (yet!)");
     return;
   }
 
-  Extension::Location location = Extension::INTERNAL;
-  LookupExternalExtension(extension.id(), NULL, &location);
 #if defined(OS_WIN)
-  bool from_external = Extension::IsExternalLocation(location);
-
-  if (!extension.IsTheme() && !from_external &&
+  if (!extension.IsTheme() &&
+      !Extension::IsExternalLocation(location) &&
       frontend_->show_extensions_prompts() &&
       win_util::MessageBox(GetForegroundWindow(),
           L"Are you sure you want to install this extension?\n\n"