Track Hydrogen statistics on a per-Isolate basis

src/isolate.cc

Index: src/isolate.cc
diff --git a/src/isolate.cc b/src/isolate.cc
index 98469a98dc06c777694581dd0f8786f625e3118d..5129dbd96e65047c64c4139b661a7a6415eb55b1 100644
--- a/src/isolate.cc
+++ b/src/isolate.cc
@@ -1792,7 +1792,7 @@ void Isolate::Deinit() {
       delete[] marking_thread_;
     }
 
-    if (FLAG_hydrogen_stats) HStatistics::Instance()->Print();
+    if (FLAG_hydrogen_stats) GetHStatistics()->Print();
 
     // We must stop the logger before we tear down other components.
     logger_->EnsureTickerStopped();
@@ -2318,6 +2318,12 @@ void Isolate::UnlinkDeferredHandles(DeferredHandles* deferred) {
 }
 
 
+HStatistics* Isolate::GetHStatistics() {
+  if (hstatistics() == NULL) set_hstatistics(new HStatistics());
+  return hstatistics();
+}
+
+
 HTracer* Isolate::GetHTracer() {
   if (htracer() == NULL) set_htracer(new HTracer(id()));
   return htracer();