Add the concept of a V8 extras exports object

src/runtime/runtime-test.cc

Index: src/runtime/runtime-test.cc
diff --git a/src/runtime/runtime-test.cc b/src/runtime/runtime-test.cc
index ddf2e9d6b46a6c7b6b848ae9754f293ef27381f2..4c49d327b2b710ed0b52086adca01017ae115460 100644
--- a/src/runtime/runtime-test.cc
+++ b/src/runtime/runtime-test.cc
@@ -364,6 +364,12 @@ RUNTIME_FUNCTION(Runtime_NativeScriptsCount) {
 }
 
 
+RUNTIME_FUNCTION(Runtime_NativeExtrasCount) {
+  DCHECK(args.length() == 0);
+  return Smi::FromInt(ExtraNatives::GetBuiltinsCount());
+}
+
+
 // Returns V8 version as a string.
 RUNTIME_FUNCTION(Runtime_GetV8Version) {
   HandleScope scope(isolate);