[Affected versions]: - Firefox 52 beta 1 build 2 - latest Developer Edition 53.0a2 [Unaffected versions]: - latest Nightly 54.0a1 (I tried multiple times) [Affected platforms]: - Windows 7 64-bit - macOS 10.12.2 - Ubuntu 16.04 64-bit [Steps to reproduce]: 1. Start Firefox. 2. Visit http://labs.jensimmons.com/examples/grid-content-1.html. 3. Open inspector and activate grid tool. 4. Activate Offline Mode (Menu/File/Offline Mode). 5. Visit http://labs.jensimmons.com/examples/grid-content-1.html in a new tab. 6. Open inspector and activate grid tool. [Expected result]: - Grid highlighter is properly displayed. [Actual result]: - The grid does not work. Console output: http://pastebin.com/68pkxjsL [Regression range]: - This is not a regression, it also reproduce on old Nightly build from 2016-11-17, when the toggle grid layout highlighter was introduced. [Additional information]: - Here is a screencast showing the issue in question: https://dl.dropboxusercontent.com/u/109148197/CSS%20Grid%20Inspector/Grid%20offline%20mode.mov The video is too large to upload it here.

Thanks for filling this. I was able to reproduce easily n latest Nightly, it seems however that on my repo this issue is not present; it could be due bug 1312103; I'll keep on eye on this bug to see if it still happens once bug 1312103 is landed.

As mentioned in comment 1, I can't reproduce it anymore now that bug 1312103 has landed. Bogdan, I think you also confirm that in your report for the grid inspector, so I'm going to close this bug as DUPLICATE – since it was fixed by apz patch –; if I'm wrong feel free to reopen it!

(In reply to Matteo Ferretti [:zer0] [:matteo] from comment #2) > As mentioned in comment 1, I can't reproduce it anymore now that bug 1312103 > has landed. > Bogdan, I think you also confirm that in your report for the grid inspector, > so I'm going to close this bug as DUPLICATE – since it was fixed by apz > patch –; if I'm wrong feel free to reopen it! You are correct, I can't see this in Nightly anymore (where bug 1312103 landed).