Google Chrome Helper (not responding)
You can see developers from the Google Chrome team discussing the issue here.

If I'm reading correctly, something triggers a change in the way things are drawn to the screen. The WindowServer process, which is responsible for drawing everything to the screen, issues a notification announcing that change to every process with a GUI and expects an acknowledgement of the notification. These Chrome processes don't respond, so the operating system flags the processes as "Not responding".

Long story short is that they think this is just a cosmetic problem that will be fixed shortly. It doesn't actually seem to affect performance.

They've found and fixed similar issues in the past, for example 304860. I think this is a side-effect of the multi-process architecture that they use for Chrome.