Strange slow down and frozen like behaviour of Google Chrome Version 40.0.2214.115 (64-bit) on Yosemite
Here are some things you can do to try to restore performance within Chrome within your own account. You could try each one at a time and see if it makes a difference.

Extensions

Open the extensions tab from the Chrome's Window menu. Try disabling all the extensions and running Chrome again to see if performance has improved. 

Saved Application State

Close Chrome. Look for Chrome's saved application state folder within your account. You should find it at /Users/YOURUSERNAME/Library/Saved Application State/com.google.Chrome.savedState. You can delete or rename the folder, it just keeps a record of which windows were open when you closed the application and what state they were in i.e. which sites you had open.

Cache folder

Delete the /Users/YOURUSERNAME/Library/Caches/Google/Chrome folder and try Chrome again. Chrome will automatically recreate this folder.

Application Support folder

This folder contains a lot of things like cookies, history, extensions, some cached files, etc. So I'd try renaming the /Users/YOURUSERNAME/Library/Application Support/Google/Chrome folder and trying again. Chrome will automatically create a new folder. If it makes no difference to performance, delete the new one and rename the old one back.

Preference list file

Within /Users/YOURUSERNAME/Library/Preferences you should find the Chrome preference file.


  com.google.chrome.plist


Just rename the file and try Chrome again. Chrome will create a new one. As with before, try with the new file, but if it makes no difference just delete the new one and rename the old one back.

Still not performing well?

You could try running sudo opensnoop | grep Chrome in a Terminal window and checking it when performance degrades. Perhaps it is trying and struggling to do something.

You could also try checking the Console.app for Chrome related error messages. Just open Console.app and type Chrome into the search field in the top-right corner of the window.

Good luck!