chrome canvas inspector 2015

Chrome and Firefox have both removed their Canvas inspectors...

Original Answer:
This is not exactly what the question asks for, but Firefox has a canvas inspector integrated: https://hacks.mozilla.org/2014/03/introducing-the-canvas-debugger-in-firefox-developer-tools/

You can enable it in the settings of the normal inspector

EDIT: (2019)
The Canvas Inspector has been removed as of Firefox 67:
Mozilla deprecated listing
Bug report with reasoning

Alternative:
spector.js - Recommended alternative by Mozilla

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.