api accessor store ics should return passed value

src/x64/code-stubs-x64.cc

Index: src/x64/code-stubs-x64.cc
diff --git a/src/x64/code-stubs-x64.cc b/src/x64/code-stubs-x64.cc
index 0637bd2fb928ac1d0f4bea03afab158eedf85d4e..8c5a430014de2658879369f53378c2dd251dac05 100644
--- a/src/x64/code-stubs-x64.cc
+++ b/src/x64/code-stubs-x64.cc
@@ -5177,7 +5177,7 @@ void CallApiFunctionStub::Generate(MacroAssembler* masm) {
   Register context = rsi;
 
   int argc = ArgumentBits::decode(bit_field_);
-  bool restore_context = RestoreContextBits::decode(bit_field_);
+  bool is_store = IsStoreBits::decode(bit_field_);
   bool call_data_undefined = CallDataUndefinedBits::decode(bit_field_);
 
   typedef FunctionCallbackArguments FCA;
@@ -5253,19 +5253,21 @@ void CallApiFunctionStub::Generate(MacroAssembler* masm) {
 
   Address thunk_address = FUNCTION_ADDR(&InvokeFunctionCallback);
 
-  StackArgumentsAccessor args_from_rbp(rbp, FCA::kArgsLength,
+  // Accessor for FunctionCallbackInfo and first js arg.
+  StackArgumentsAccessor args_from_rbp(rbp, FCA::kArgsLength + 1,
                                        ARGUMENTS_DONT_CONTAIN_RECEIVER);
   Operand context_restore_operand = args_from_rbp.GetArgumentOperand(
-      FCA::kArgsLength - 1 - FCA::kContextSaveIndex);
+      FCA::kArgsLength - FCA::kContextSaveIndex);
+  // Stores return the first js argument
   Operand return_value_operand = args_from_rbp.GetArgumentOperand(
-      FCA::kArgsLength - 1 - FCA::kReturnValueOffset);
+      is_store ? 0 : FCA::kArgsLength - FCA::kReturnValueOffset);
   __ CallApiFunctionAndReturn(
       api_function_address,
       thunk_address,
       callback_arg,
       argc + FCA::kArgsLength + 1,
       return_value_operand,
-      restore_context ? &context_restore_operand : NULL);
+      &context_restore_operand);
 }