I am using chrome version 36+
according to this page, I should be able to allow custom themes using the following instructions:
Installation Inst
loislo's answer is absolutely right (You need to restart the browser after changing the flag at chrome://flags). But notice that your chrome can work in the background. Go to the tray, look for the chrome icon and exit.
Had the same issue,
I found I was going to browser settings which is NOT where you should be going to , You need to go to developer setting .
i.e right click>inspect element> dev tools
You need to restart the browser after changing the flag at chrome://flags
Restart chrome just not means to close the chrome and then open it. you should click the 'Relaunch Now' button of the flags tab. and then it's work for me.
Navigate to chrome://flags/
Find and enable Developer Tools experiments Mac, Windows, Linux, Chrome OS
Relaunch Chrome, open develop tool, setting, you will see experiments tab.
My Chrome version: Version 61.0.3163.100
To get to the Dev Tools Experiments area you have to click on the gear icon in the inspector.
If still not working you should go to:
chrome://extensions/
And click the 'Enable' checkbox for the DevTools extension you wish to enable.