Expose counters in javascript.

src/bootstrapper.cc

Index: src/bootstrapper.cc
diff --git a/src/bootstrapper.cc b/src/bootstrapper.cc
index 726670aae54a01cffe1890fd36a9dbadb988d66d..d6d94d42043008b61435430a5ad12595723efad5 100644
--- a/src/bootstrapper.cc
+++ b/src/bootstrapper.cc
@@ -42,6 +42,7 @@
 #include "snapshot.h"
 #include "extensions/externalize-string-extension.h"
 #include "extensions/gc-extension.h"
+#include "extensions/counters-extension.h"
 
 namespace v8 {
 namespace internal {
@@ -95,6 +96,7 @@ void Bootstrapper::Initialize(bool create_heap_objects) {
   extensions_cache_.Initialize(create_heap_objects);
   GCExtension::Register();
   ExternalizeStringExtension::Register();
+  CountersExtension::Register();
 }
 
 
@@ -1997,6 +1999,9 @@ bool Genesis::InstallExtensions(Handle<Context> global_context,
   if (FLAG_expose_externalize_string) {
     InstallExtension("v8/externalize", &extension_states);
   }
+  if (FLAG_track_gc_object_stats) {
+    InstallExtension("v8/counters", &extension_states);
+  }
 
   if (extensions == NULL) return true;
   // Install required extensions