Expose counters in javascript.

src/extensions/counters-extension.h

 // Copyright 2010 the V8 project authors. All rights reserved.
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 // modification, are permitted provided that the following conditions are
 // met:
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-#ifndef V8_EXTENSIONS_GC_EXTENSION_H_
-#define V8_EXTENSIONS_GC_EXTENSION_H_
+#ifndef V8_EXTENSIONS_COUNTERS_EXTENSION_H_
+#define V8_EXTENSIONS_COUNTERS_EXTENSION_H_
 
 #include "v8.h"
 
 namespace v8 {
 namespace internal {
 
-class GCExtension : public v8::Extension {
+class CountersExtension : public v8::Extension {
  public:
-  GCExtension() : v8::Extension("v8/gc", kSource) {}
+  CountersExtension() : v8::Extension("v8/counters", kSource) {}
   virtual v8::Handle<v8::FunctionTemplate> GetNativeFunction(
       v8::Handle<v8::String> name);
-  static v8::Handle<v8::Value> GC(const v8::Arguments& args);
+  static v8::Handle<v8::Value> GetCounters(const v8::Arguments& args);
   static void Register();
  private:
   static const char* const kSource;
 };
 
 } }  // namespace v8::internal
 
-#endif  // V8_EXTENSIONS_GC_EXTENSION_H_
+#endif  // V8_EXTENSIONS_COUNTERS_EXTENSION_H_