I used this nifty feature that chrome had for quite a while called \"canvas inspector\". It was an experimental dev feature that had to manually be enabled.
It was
Apparently it was doing some cheeky stuff that they didn't want in the main project so it was removed in this issue: DevTools: make Canvas profiler an extension
We can make it an extension though. This bug is for tracking removal of the canvas profiler from the DevTools. There will be a separate initiative of porting the code being removed into github and publishing it as a Chrome extension.
According to that issue they might move it to an extension in the future but I haven't found any traces of it as of now. They haven't responded to a question in the above issue about where the new issue could be tracked.