Created attachment 8480246 [details] log An automated test I am working on does the following: Load a page in a tab. Click a link in the page which will trigger a new tab to open. Wait for the TabOpen event. Close the new tab immediately. Randomly this will cause the child process to crash because the TabParent has been destroyed before the TabChild has finished initialising, specifically creating the PRenderFrame. Attached is a log showing this happening, I added some additional logs to TabParent calls, you can see that TabParent 0x11d337c00 is created then later destroyed and its mOwnerElement nulled out. Later the child calls AllocPRenderFrameParent which fails because there is no longer a frameloader. I can fix the test by having it wait for the tab to load before closing but I suspect this might be a common thing in browser-chrome tests so it might be a good idea to fix this.