Fix a duplicate AST ID recorded for for/in.

src/x64/full-codegen-x64.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 1668 matching lines @@
       VisitForAccumulatorValue(prop->obj());
       __ movq(rdx, rax);
       __ pop(rax);  // Restore value.
       __ Move(rcx, prop->key()->AsLiteral()->handle());
       Handle<Code> ic(Builtins::builtin(Builtins::StoreIC_Initialize));
       EmitCallIC(ic, RelocInfo::CODE_TARGET);
       break;
     }
     case KEYED_PROPERTY: {
       __ push(rax);  // Preserve value.
-      VisitForStackValue(prop->obj());
-      VisitForAccumulatorValue(prop->key());
-      __ movq(rcx, rax);
-      __ pop(rdx);
-      __ pop(rax);
+      if (prop->is_synthetic()) {
+        ASSERT(prop->obj()->AsVariableProxy() != NULL);
+        ASSERT(prop->key()->AsLiteral() != NULL);
+        { AccumulatorValueContext for_object(this);
+          EmitVariableLoad(prop->obj()->AsVariableProxy()->var());
+        }
+        __ movq(rdx, rax);
+        __ Move(rcx, prop->key()->AsLiteral()->handle());
+      } else {
+        VisitForStackValue(prop->obj());
+        VisitForAccumulatorValue(prop->key());
+        __ movq(rcx, rax);
+        __ pop(rdx);
+      }
+      __ pop(rax);  // Restore value.
       Handle<Code> ic(Builtins::builtin(Builtins::KeyedStoreIC_Initialize));
       EmitCallIC(ic, RelocInfo::CODE_TARGET);
       break;
     }
   }
   PrepareForBailoutForId(bailout_ast_id, TOS_REG);
   context()->Plug(rax);
 }
 
 
@@ skipping 2042 matching lines @@
   __ ret(0);
 }
 
 
 #undef __
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64