The unit tests are timing out and the inspector doesn't show up in MiniBrowser either. It seems that after r179705 the initial attach message is never received in the UI process.
The following code was moved out of the static PageGroup management code. It was re-added in a platform-specific way for PLATFORM(MAC), so maybe it has to be re-added to GTK/EFL when the PageGroup is constructed. (On Mac, Inspector now uses WKWebView which only takes the group identifier. So we first construct the view, then adjust prefs, then do the initial load.)
// Allow developers to inspect the Web Inspector in debug builds without changing settings.
Yes, that was it, thanks!
Created attachment 246240 [details]
Committed r179821: <http://trac.webkit.org/changeset/179821>