Bug 1034239 - Add Proxies to ForceCOWBehavior. r=gabor

js/xpconnect/wrappers/WrapperFactory.cpp

@@ -121,9 +121,8 @@ WrapperFactory::DoubleWrap(JSContext *cx, HandleObject obj, unsigned flags)
 }
 
 // In general, we're trying to deprecate COWs incrementally as we introduce
-// Xrays to the corresponding object types. But switching off COWs for Object
-// and Array instances would be too tumultuous at present, so we punt on that
-// for later.
+// Xrays to the corresponding object types. But switching off COWs for certain
+// things would be too tumultuous at present, so we punt on them for later.
 static bool
 ForceCOWBehavior(JSObject *obj)
 {
@@ -134,6 +133,11 @@ ForceCOWBehavior(JSObject *obj)
                    "instances modulo this hack");
         return true;
     }
+    // Proxies get OpaqueXrayTraits, but we still need COWs to them for now to
+    // let the SpecialPowers wrapper work.
+    if (key == JSProto_Proxy)
+        return true;
+
     return false;
 }