禁用按钮属性在Google Chrome中无效

I have a button Upload where in file will be uploaded, But the requirement is when is selected a file and then press Upload button.The button should be disabled until the process occurs with complete validation issues.

The code i have written is shown below.

 <form id='FM_EmployeeUpload' name='FM_EmployeeUpload' method='post' action='new_S_EmployeeUpload.php' enctype='multipart/form-data'>

 echo('<input type="submit" class="btn btn-lg pull-left" name="submit" onClick="DisableButton();" id="Upload" value="UPLOAD"/>&nbsp;');

  </form>

function DisableButton(){
        document.getElementById("Upload").disabled = true;
}

Now the problem arises with the Browsers when i do this task on Firefox if there is error in uploading the file Validation issues will takes place and it will work perfect.The screen shot is shown below. IN FIREFOX

But the same code i run in Google Chrome No validation nothing will happen ony the button will e disabled some what looks like this.

IN CHROME

What is the main issue regarding the problem. Any help appreciated.