In KDE I turned off shadows in my theme but noticed the Google Chrome window still had a large shadow at the bottom. I used these steps to force it off.
- In Chrome right click the empty space to the right of the tabs.
- Select "Use system title bar and borders" (turn it ON)
- Right-click the new KDE title bar now showing for Chrome.
- Go to More Actions > Configure Special Window Settings
- Click Add Property then scroll down and pick Block compositing
- Select 'Yes' and 'Force'
- Click Apply , Okay.
- Go back into Chrome.
- Right click at top and turn off 'Use system title bar and border'.
The shadow is now gone.
