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

extensions/renderer/script_context_set_unittest.cc

Index: extensions/renderer/script_context_set_unittest.cc
diff --git a/extensions/renderer/script_context_set_unittest.cc b/extensions/renderer/script_context_set_unittest.cc
index 580fc25ddd5f0504385f8ab46953dd3be2d7deeb..58dd1aec748fc00ebddd4bf4f173f5d02d1a45cb 100644
--- a/extensions/renderer/script_context_set_unittest.cc
+++ b/extensions/renderer/script_context_set_unittest.cc
@@ -27,7 +27,7 @@ TEST(ScriptContextSet, Lifecycle) {
   // Dirty hack, but we don't actually need the frame, and this is easier than
   // creating a whole webview.
   blink::WebFrame* frame = reinterpret_cast<blink::WebFrame*>(1);
-  const Extension* extension = NULL;
+  const Extension* extension = nullptr;
   ScriptContext* context =
       new ScriptContext(context_holder.context(),
                         frame,