Pinyin input placed behind Hangouts window
You can disable the on top feature of that window. 


  "Change settings that apply only for the Hangouts Chrome desktop app
  Click the Chrome launcher icon . If you're using Windows, you may see
  a window asking you to sign in to your Chrome browser. Sign in with
  your Google Account. Click the Hangouts Chrome desktop app . At the
  top of your Hangouts list, click settings . Choose one of the settings
  below to change. Keep in mind these settings only apply to the Chrome
  desktop app, not Hangouts in Gmail, Google+ or the Chrome extension.
  Start Hangouts app when Chrome starts: Check this box to start the
  Chrome desktop app whenever you start Chrome. Always on top: Check
  this box to see the Chrome desktop app on top of all other apps or
  browsers that you have open on your computer. Uncheck this box to undo
  the setting. Auto-hide conversations: Check this box to automatically
  minimize the conversation windows when you're not clicked in the
  actual chat window. Uncheck this box to undo the setting. Show message
  preview for new message: Check this box to show a preview of a new
  Hangout message. Uncheck this box to undo the setting."


https://support.google.com/hangouts/answer/6101837?hl=en