If content script didn't work the DevTools tab should inject the winodw.breakpoints object

[mattzeunert]

For example, right after installing the extension the content script hasn't been injected into any pages that have already been loaded. However, it's possible to open the DevTools on those pages and see the breakpoints tab.

Generally, if the breakpoints object can't be found the DevTools tab should inject it.

[mattzeunert]

Done.