Fix for 3303 MultithreadedParallelIsolates has a race condition.

src/isolate.cc

Index: src/isolate.cc
diff --git a/src/isolate.cc b/src/isolate.cc
index 72df9b4b2b131794190e025049fe65f4e8e51362..1962454346558dfa363e700fe581b45a591ecf35 100644
--- a/src/isolate.cc
+++ b/src/isolate.cc
@@ -133,8 +133,8 @@ Isolate::PerIsolateThreadData*
       per_thread = new PerIsolateThreadData(this, thread_id);
       thread_data_table_->Insert(per_thread);
     }
+    ASSERT(thread_data_table_->Lookup(this, thread_id) == per_thread);
   }
-  ASSERT(thread_data_table_->Lookup(this, thread_id) == per_thread);
   return per_thread;
 }
 
@@ -1426,6 +1426,7 @@ Isolate::Isolate()
       logger_(NULL),
       stats_table_(NULL),
       stub_cache_(NULL),
+      code_aging_helper_(NULL),
       deoptimizer_data_(NULL),
       materialized_object_store_(NULL),
       capture_stack_trace_for_uncaught_exceptions_(false),
@@ -1660,6 +1661,8 @@ Isolate::~Isolate() {
 
   delete stub_cache_;
   stub_cache_ = NULL;
+  delete code_aging_helper_;
+  code_aging_helper_ = NULL;
   delete stats_table_;
   stats_table_ = NULL;
 
@@ -1848,6 +1851,8 @@ bool Isolate::Init(Deserializer* des) {
 #endif
 #endif
 
+  code_aging_helper_ = new CodeAgingHelper();
+
   { // NOLINT
     // Ensure that the thread has a valid stack guard.  The v8::Locker object
     // will ensure this too, but we don't have to use lockers if we are only