Bug 1346902 - Re-enable new debugger UI for Browser Toolbox. r=Gijs,rpl

It appears the new debugger UI is working for the Browser Toolbox case, so let's
turn it on to match our approach with web content.

MozReview-Commit-ID: 1HhSKwZMH2f

--HG--
extra : rebase_source : e879a84c894e5f21eeaf47f8d116c02364114989

devtools/client/framework/toolbox-process-window.js

@@ -70,7 +70,7 @@ function setPrefDefaults() {
   Services.prefs.setBoolPref("devtools.scratchpad.enabled", true);
   // Bug 1225160 - Using source maps with browser debugging can lead to a crash
   Services.prefs.setBoolPref("devtools.debugger.source-maps-enabled", false);
-  Services.prefs.setBoolPref("devtools.debugger.new-debugger-frontend", false);
+  Services.prefs.setBoolPref("devtools.debugger.new-debugger-frontend", true);
   Services.prefs.setBoolPref("devtools.debugger.client-source-maps-enabled", true);
 }