Run clang-modernize -use-nullptr over src/extensions/.

extensions/browser/api/declarative/test_rules_registry.cc

Index: extensions/browser/api/declarative/test_rules_registry.cc
diff --git a/extensions/browser/api/declarative/test_rules_registry.cc b/extensions/browser/api/declarative/test_rules_registry.cc
index 030a22a83a969413e24cebf82be7a4bc8ae0fa92..e79459c2dc83bd3cefc19f2cf0dc41a73cd80a46 100644
--- a/extensions/browser/api/declarative/test_rules_registry.cc
+++ b/extensions/browser/api/declarative/test_rules_registry.cc
@@ -11,11 +11,12 @@ namespace extensions {
 TestRulesRegistry::TestRulesRegistry(content::BrowserThread::ID owner_thread,
                                      const std::string& event_name,
                                      const WebViewKey& webview_key)
-    : RulesRegistry(NULL /*profile*/,
+    : RulesRegistry(nullptr /*profile*/,
                     event_name,
                     owner_thread,
-                    NULL,
-                    webview_key) {}
+                    nullptr,
+                    webview_key) {
+}
 
 TestRulesRegistry::TestRulesRegistry(
     content::BrowserContext* browser_context,