Remove NOTIFICATION_EXTENSION_ENABLED.

extensions/browser/extension_registry.cc

Index: extensions/browser/extension_registry.cc
diff --git a/extensions/browser/extension_registry.cc b/extensions/browser/extension_registry.cc
index 24ef83b54c86e432ffc7d15096cdf45ea177e5a8..53c0195f7eea665d8d6520dafaec9e32aff15001 100644
--- a/extensions/browser/extension_registry.cc
+++ b/extensions/browser/extension_registry.cc
@@ -4,6 +4,7 @@
 
 #include "extensions/browser/extension_registry.h"
 
+#include "base/memory/ptr_util.h"
 #include "base/strings/string_util.h"
 #include "extensions/browser/extension_registry_factory.h"
 #include "extensions/browser/extension_registry_observer.h"
@@ -11,7 +12,11 @@
 namespace extensions {
 
 ExtensionRegistry::ExtensionRegistry(content::BrowserContext* browser_context)
-    : browser_context_(browser_context) {}
+    : browser_context_(browser_context) {
+  lazy_event_dispatch_util_ =
+      base::MakeUnique<LazyEventDispatchUtil>(browser_context_, this);
+}
+
 ExtensionRegistry::~ExtensionRegistry() {}
 
 // static
@@ -215,6 +220,11 @@ void ExtensionRegistry::Shutdown() {
   ClearAll();
   for (auto& observer : observers_)
     observer.OnShutdown(this);
+  lazy_event_dispatch_util_.reset();
+}
+
+LazyEventDispatchUtil* ExtensionRegistry::lazy_event_dispatch_util() {
+  return lazy_event_dispatch_util_.get();
 }
 
 }  // namespace extensions