Strict mode eval declares its locals in its own environment.

src/parser.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 1285 matching lines @@
   // If we are inside a function, a declaration of a variable
   // is a truly local variable, and the scope of the variable
   // is always the function scope.
 
   // If a function scope exists, then we can statically declare this
   // variable and also set its mode. In any case, a Declaration node
   // will be added to the scope so that the declaration can be added
   // to the corresponding activation frame at runtime if necessary.
   // For instance declarations inside an eval scope need to be added
   // to the calling function context.
-  if (top_scope_->is_function_scope()) {
+  // Similarly, strict mode eval scope does not leak variable declarations to
+  // the caller's scope so we declare all locals, too.
+  if (top_scope_->is_function_scope() ||
+      top_scope_->is_strict_mode_eval_scope()) {
     // Declare the variable in the function scope.
     var = top_scope_->LocalLookup(name);
     if (var == NULL) {
       // Declare the name.
       var = top_scope_->DeclareLocal(name, mode);
     } else {
       // The name was declared before; check for conflicting
       // re-declarations. If the previous declaration was a const or the
       // current declaration is a const then we have a conflict. There is
       // similar code in runtime.cc in the Declare functions.
@@ skipping 3834 matching lines @@
                                    info->is_global(),
                                    info->StrictMode());
     }
   }
 
   info->SetFunction(result);
   return (result != NULL);
 }
 
 } }  // namespace v8::internal