Fix for 3303 MultithreadedParallelIsolates has a race condition.

src/isolate.h

Index: src/isolate.h
diff --git a/src/isolate.h b/src/isolate.h
index fdd89b4f4e605fc06834200079e343c4bb96d695..185d7ea4a008c7cc4d7f9f6d23b9655d64c8be9a 100644
--- a/src/isolate.h
+++ b/src/isolate.h
@@ -54,6 +54,7 @@ class InlineRuntimeFunctionsTable;
 class InnerPointerToCodeCache;
 class MaterializedObjectStore;
 class NoAllocationStringAllocator;
+class CodeAgingHelper;
 class RandomNumberGenerator;
 class RegExpStack;
 class SaveContext;
@@ -836,6 +837,7 @@ class Isolate {
   Heap* heap() { return &heap_; }
   StatsTable* stats_table();
   StubCache* stub_cache() { return stub_cache_; }
+  CodeAgingHelper* code_aging_helper() { return code_aging_helper_; }
   DeoptimizerData* deoptimizer_data() { return deoptimizer_data_; }
   ThreadLocalTop* thread_local_top() { return &thread_local_top_; }
   MaterializedObjectStore* materialized_object_store() {
@@ -1203,6 +1205,7 @@ class Isolate {
   StackGuard stack_guard_;
   StatsTable* stats_table_;
   StubCache* stub_cache_;
+  CodeAgingHelper* code_aging_helper_;
   DeoptimizerData* deoptimizer_data_;
   MaterializedObjectStore* materialized_object_store_;
   ThreadLocalTop thread_local_top_;