Link function contexts directly to the previous context.

src/heap.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 3910 matching lines @@
 MaybeObject* Heap::AllocateFunctionContext(int length, JSFunction* function) {
   ASSERT(length >= Context::MIN_CONTEXT_SLOTS);
   Object* result;
   { MaybeObject* maybe_result = AllocateFixedArray(length);
     if (!maybe_result->ToObject(&result)) return maybe_result;
   }
   Context* context = reinterpret_cast<Context*>(result);
   context->set_map(function_context_map());
   context->set_closure(function);
   context->set_fcontext(context);
-  context->set_previous(NULL);
+  context->set_previous(function->context());
   context->set_extension(NULL);
   context->set_global(function->context()->global());
   return context;
 }
 
 
 MaybeObject* Heap::AllocateCatchContext(Context* previous,
                                         JSObject* extension) {
   Object* result;
   { MaybeObject* maybe_result = AllocateFixedArray(Context::MIN_CONTEXT_SLOTS);
@@ skipping 2089 matching lines @@
 }
 
 
 void ExternalStringTable::TearDown() {
   new_space_strings_.Free();
   old_space_strings_.Free();
 }
 
 
 } }  // namespace v8::internal