Do not assume that names of function expressions are context-allocated.

src/objects.h

 // Copyright 2012 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 3395 matching lines @@
   // mode for that variable.
   int ContextSlotIndex(String* name,
                        VariableMode* mode,
                        InitializationFlag* init_flag);
 
   // Lookup support for serialized scope info. Returns the
   // parameter index for a given parameter name if the parameter is present;
   // otherwise returns a value < 0. The name must be a symbol (canonicalized).
   int ParameterIndex(String* name);
 
-  // Lookup support for serialized scope info. Returns the
-  // function context slot index if the function name is present (named
+  // Lookup support for serialized scope info. Returns the function context
+  // slot index if the function name is present and context-allocated (named
   // function expressions, only), otherwise returns a value < 0. The name
   // must be a symbol (canonicalized).
   int FunctionContextSlotIndex(String* name, VariableMode* mode);
 
   static Handle<ScopeInfo> Create(Scope* scope);
 
   // Serializes empty scope info.
   static ScopeInfo* Empty();
 
 #ifdef DEBUG
@@ skipping 5166 matching lines @@
     } else {
       value &= ~(1 << bit_position);
     }
     return value;
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_H_