Steps To Reproduce:

Steps To Reproduce: 1. Enable e10s 2. Attempt to open Web Console Regression window(fx) Good: https://hg.mozilla.org/integration/fx-team/rev/1e0e069b5cc7 Mozilla/5.0 (Windows NT 6.1; WOW64; rv:35.0) Gecko/20100101 Firefox/35.0 ID:20140912150609 Bad: https://hg.mozilla.org/integration/fx-team/rev/a6d02cff43d3 Mozilla/5.0 (Windows NT 6.1; WOW64; rv:35.0) Gecko/20100101 Firefox/35.0 ID:20140912201609 Pushlog: http://hg.mozilla.org/integration/fx-team/pushloghtml?fromchange=1e0e069b5cc7&tochange=a6d02cff43d3 Suspect: Bug 1037235

The developer console does indeed fail to open (both in "New e10s window", or while e10s is enabled by default). The browser console displays several error messages when trying to open the when one tries to open the dev console (ie. by pressing F12). The browser console appears as a completely blank window/sidebar (depending on last open configuration) and can not be closed. See the generated error messages in the browser control in the attachment (note: the browser console needs to be opened from a non-e10s window, as current e10s implementation fails to open the browser console altogether from an e10s window - see bug 1067120).

I can confirm that after disabling e10s (in Settings) and restarting Nightly, the DevTools show up again.

fixed by backout