Link function contexts directly to the previous context.

src/runtime.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 8589 matching lines @@
   // it is bound in the global context.
   int index = -1;
   PropertyAttributes attributes = ABSENT;
   while (true) {
     receiver = context->Lookup(isolate->factory()->eval_symbol(),
                                FOLLOW_PROTOTYPE_CHAIN,
                                &index, &attributes);
     // Stop search when eval is found or when the global context is
     // reached.
     if (attributes != ABSENT || context->IsGlobalContext()) break;
-    if (context->IsFunctionContext()) {
-      context = Handle<Context>(context->closure()->context(), isolate);
-    } else {
-      context = Handle<Context>(context->previous(), isolate);
-    }
+    context = Handle<Context>(context->previous(), isolate);
   }
 
   // If eval could not be resolved, it has been deleted and we need to
   // throw a reference error.
   if (attributes == ABSENT) {
     Handle<Object> name = isolate->factory()->eval_symbol();
     Handle<Object> reference_error =
         isolate->factory()->NewReferenceError("not_defined",
                                               HandleVector(&name, 1));
     return MakePair(isolate->Throw(*reference_error), NULL);
@@ skipping 1636 matching lines @@
       }
     }
 
     // The global scope is always the last in the chain.
     if (context_->IsGlobalContext()) {
       context_ = Handle<Context>();
       return;
     }
 
     // Move to the next context.
-    if (context_->IsFunctionContext()) {
-      context_ = Handle<Context>(context_->closure()->context());
-    } else {
-      context_ = Handle<Context>(context_->previous());
-    }
+    context_ = Handle<Context>(context_->previous(), isolate_);
 
     // If passing the local scope indicate that the current scope is now the
     // local scope.
     if (!local_done_ &&
         (context_->IsGlobalContext() || context_->IsFunctionContext())) {
       at_local_ = true;
     }
   }
 
   // Return the type of the current scope.
@@ skipping 2077 matching lines @@
   } else {
     // Handle last resort GC and make sure to allow future allocations
     // to grow the heap without causing GCs (if possible).
     isolate->counters()->gc_last_resort_from_js()->Increment();
     isolate->heap()->CollectAllGarbage(false);
   }
 }
 
 
 } }  // namespace v8::internal