Disable extensions besides externally installed ones and themes.

chrome/browser/extensions/extensions_service.h

Index: chrome/browser/extensions/extensions_service.h
diff --git a/chrome/browser/extensions/extensions_service.h b/chrome/browser/extensions/extensions_service.h
index f2f0b566b87b6585191bffbda7f2dfc74fb1d3c1..87c387faedf4f2cd3184150859d85cdac21cbe9d 100644
--- a/chrome/browser/extensions/extensions_service.h
+++ b/chrome/browser/extensions/extensions_service.h
@@ -132,12 +132,13 @@ class ExtensionsService
   // The name of the file that the current active version number is stored in.
   static const char* kCurrentVersionFileName;
 
-  void set_extensions_enabled(bool enabled) { extensions_enabled_ = enabled; }
+  void SetExtensionsEnabled(bool enabled);
+  bool extensions_enabled() { return extensions_enabled_; }
+
   void set_show_extensions_prompts(bool enabled) {
     show_extensions_prompts_ = enabled;
   }
 
-  bool extensions_enabled() { return extensions_enabled_; }
   bool show_extensions_prompts() {
     return show_extensions_prompts_;
   }
@@ -209,10 +210,13 @@ class ExtensionsServiceBackend
   ExtensionsServiceBackend(const FilePath& install_directory,
                            ResourceDispatcherHost* rdh,
                            MessageLoop* frontend_loop,
-                           DictionaryValue* extension_prefs);
+                           DictionaryValue* extension_prefs,
+                           bool extensions_enabled);
 
   virtual ~ExtensionsServiceBackend();
 
+  void set_extensions_enabled(bool enabled) { extensions_enabled_ = enabled; }
+
   // Loads the installed extensions.
   // Errors are reported through ExtensionErrorReporter. On completion,
   // OnExtensionsLoaded() is called with any successfully loaded extensions.
@@ -399,6 +403,10 @@ class ExtensionsServiceBackend
   // The message loop to use to call the frontend.
   MessageLoop* frontend_loop_;
 
+  // Whether non-theme extensions are enabled (themes and externally registered
+  // extensions are always enabled).
+  bool extensions_enabled_;
+
   // A map of all external extension providers.
   typedef std::map<Extension::Location,
                    linked_ptr<ExternalExtensionProvider> > ProviderMap;