Bug 1412456 - Disable add-on interposition (r=mconley)

MozReview-Commit-ID: 3burzHHoHlX

browser/app/profile/firefox.js

@@ -1586,7 +1586,7 @@ pref("browser.tabs.crashReporting.emailMe", false);
 pref("browser.tabs.crashReporting.email", "");
 
 // Enable e10s add-on interposition by default.
-pref("extensions.interposition.enabled", true);
+pref("extensions.interposition.enabled", false);
 pref("extensions.interposition.prefetching", true);
 
 // But don't allow non-MPC extensions by default on Nightly