-allow-running-insecure-content (Chrome 38+ issue)

I have an iFrame in an HTTPS application. This iFrame calls the HTTP page to display. Therefore, due to the mixed content, Chrome does not display data, so it displays the screen button. Was there a web search and they said to add a flag to the chrome context menu.

flag: --allow-running-insecure-content

But even after adding the flag to the Target context menu, still I was not able to automatically preview the unsafe content. However, it displays the Shield icon and I have to select "Load insecure script" to display the data.

I'm using chrome 38. Is the flag above from chrome 38 ??? Or are there other ways to display unsafe content automatically in chrome ???