In MacOS in the Activity Monitor Google Chrome extensions show as "Google Chrome Helper". These often take up much of the CPU time. Is it possible to determine which tab a given Google Chrome Helper process is running on?
Other people have suggested setting the plug-ins run mode to "Click to play". It seems that this doesn't cover all instances of the helper, since I already have it set to click to play. As you can see from the image below, there are MANY instances of this helper running. Anyway this doesn't get to the heart of the question- which tab is the process running on.
Chrome's built-in Task Manager (accessible from Menu > More tools > Task manager) will show you a per-tab resource utilization.
If case the culprit is extension code or a plug-in running in a normal tab, you won't be able to identify it with only that; extension entries in the Task Manager are only for background pages of extensions.
You may be able to investigate further with Dev Tools profiler.