Track Hydrogen statistics on a per-Isolate basis

src/compiler.cc

Index: src/compiler.cc
diff --git a/src/compiler.cc b/src/compiler.cc
index 99768472e0969fa681dc055a43ea5885f546103f..100d100d3518f624c9fb643dfc1920f1e6ef8015 100644
--- a/src/compiler.cc
+++ b/src/compiler.cc
@@ -234,9 +234,9 @@ void OptimizingCompiler::RecordOptimizationStats() {
            compilation_time);
   }
   if (FLAG_hydrogen_stats) {
-    HStatistics::Instance()->IncrementSubtotals(time_taken_to_create_graph_,
-                                                time_taken_to_optimize_,
-                                                time_taken_to_codegen_);
+    isolate()->GetHStatistics()->IncrementSubtotals(time_taken_to_create_graph_,
+                                                    time_taken_to_optimize_,
+                                                    time_taken_to_codegen_);
   }
 }