Bug 973780 - Remove Xray expando slot from WNs. r=bz

js/xpconnect/src/XPCWrappedNative.cpp

@@ -859,10 +859,6 @@ XPCWrappedNative::FinishInit()
 {
     AutoJSContext cx;
 
-    // For all WNs, we want to make sure that the expando chain slot starts out
-    // as null.
-    JS_SetReservedSlot(mFlatJSObject, WN_XRAYEXPANDOCHAIN_SLOT, JSVAL_NULL);
-
     // This reference will be released when mFlatJSObject is finalized.
     // Since this reference will push the refcount to 2 it will also root
     // mFlatJSObject;
@@ -1186,7 +1182,6 @@ XPCWrappedNative::ReparentWrapperIfFound(XPCWrappedNativeScope* aOldScope,
 
             // Expandos from other compartments are attached to the target JS object.
             // Copy them over, and let the old ones die a natural death.
-            SetWNExpandoChain(newobj, nullptr);
             if (!XrayUtils::CloneExpandoChain(cx, newobj, flat))
                 return NS_ERROR_FAILURE;
 

js/xpconnect/src/xpcprivate.h

@@ -213,17 +213,10 @@ extern const char XPC_XPCONNECT_CONTRACTID[];
     return (result || !src) ? NS_OK : NS_ERROR_OUT_OF_MEMORY
 
 
-#define WRAPPER_SLOTS (JSCLASS_HAS_PRIVATE | JSCLASS_IMPLEMENTS_BARRIERS | \
-                       JSCLASS_HAS_RESERVED_SLOTS(1))
+#define WRAPPER_SLOTS (JSCLASS_HAS_PRIVATE | JSCLASS_IMPLEMENTS_BARRIERS )
 
 #define INVALID_OBJECT ((JSObject *)1)
 
-// NB: This slot isn't actually reserved for us on globals, because SpiderMonkey
-// uses the first N slots on globals internally. The fact that we use it for
-// wrapped global objects is totally broken. But due to a happy coincidence, the
-// JS engine never uses that slot. This still needs fixing though. See bug 760095.
-#define WN_XRAYEXPANDOCHAIN_SLOT 0
-
 // If IS_WN_CLASS for the JSClass of an object is true, the object is a
 // wrappednative wrapper, holding the XPCWrappedNative in its private slot.
 static inline bool IS_WN_CLASS(const js::Class* clazz)
@@ -236,18 +229,6 @@ static inline bool IS_WN_REFLECTOR(JSObject *obj)
     return IS_WN_CLASS(js::GetObjectClass(obj));
 }
 
-inline void SetWNExpandoChain(JSObject *obj, JSObject *chain)
-{
-    MOZ_ASSERT(IS_WN_REFLECTOR(obj));
-    JS_SetReservedSlot(obj, WN_XRAYEXPANDOCHAIN_SLOT, JS::ObjectOrNullValue(chain));
-}
-
-inline JSObject* GetWNExpandoChain(JSObject *obj)
-{
-    MOZ_ASSERT(IS_WN_REFLECTOR(obj));
-    return JS_GetReservedSlot(obj, WN_XRAYEXPANDOCHAIN_SLOT).toObjectOrNull();
-}
-
 /***************************************************************************
 ****************************************************************************
 *