How to Lock Your Google Chrome Browser

First Download Google Chrome Plugin Simple Startup Password

Now go to Settings -> Tools ->Extensions. 

Find Simple Startup Password and click on Options

Set a password for your browser and press save button

Restart Your Web browser

Second Method

 Download Browser Lock Chrome Plugin

Press the Ctrl+Shift+ L  (you CAN change the combination in settings) to lock or unlock. Or you can also lock it by clicking the lock icon.

You can change the password in the settings. (Go to chrome://extentions/ and press the setting button under the Browser Lock's icon.)

Restart the browser after you have done any changes in settings.