Bug 1478275 part 1 - Remove unused CompartmentPrivate::isAddonCompartment. r=bholley

js/xpconnect/src/XPCJSRuntime.cpp

@@ -215,7 +215,6 @@ CompartmentPrivate::CompartmentPrivate(JS::Compartment* c)
     , isWebExtensionContentScript(false)
     , allowCPOWs(false)
     , isContentXBLCompartment(false)
-    , isAddonCompartment(false)
     , universalXPConnectEnabled(false)
     , forcePermissiveCOWs(false)
     , wasNuked(false)

js/xpconnect/src/xpcprivate.h

@@ -2873,11 +2873,6 @@ public:
     // such a compartment is a content XBL scope.
     bool isContentXBLCompartment;
 
-    // True if EnsureAddonCompartment has been called for this compartment.
-    // Note that this is false for extensions that ship with the browser, like
-    // browser/extensions/activity-stream.
-    bool isAddonCompartment;
-
     // This is only ever set during mochitest runs when enablePrivilege is called.
     // It's intended as a temporary stopgap measure until we can finish ripping out
     // enablePrivilege. Once set, this value is never unset (i.e., it doesn't follow