Bug 1090592 - LazyProto for ProxyOptions. r=bholley

js/src/jsproxy.h

@@ -541,13 +541,15 @@ SetReservedOrProxyPrivateSlot(JSObject *obj, size_t slot, const Value &value)
 class MOZ_STACK_CLASS ProxyOptions {
   protected:
     /* protected constructor for subclass */
-    explicit ProxyOptions(bool singletonArg)
+    explicit ProxyOptions(bool singletonArg, bool lazyProtoArg = false)
       : singleton_(singletonArg),
+        lazyProto_(lazyProtoArg),
         clasp_(ProxyClassPtr)
     {}
 
   public:
     ProxyOptions() : singleton_(false),
+                     lazyProto_(false),
                      clasp_(ProxyClassPtr)
     {}
 
@@ -557,6 +559,12 @@ class MOZ_STACK_CLASS ProxyOptions {
         return *this;
     }
 
+    bool lazyProto() const { return lazyProto_; }
+    ProxyOptions &setLazyProto(bool flag) {
+        lazyProto_ = flag;
+        return *this;
+    }
+
     const Class *clasp() const {
         return clasp_;
     }
@@ -567,6 +575,7 @@ class MOZ_STACK_CLASS ProxyOptions {
 
   private:
     bool singleton_;
+    bool lazyProto_;
     const Class *clasp_;
 };
 

js/src/proxy/Proxy.cpp

@@ -753,6 +753,11 @@ JS_FRIEND_API(JSObject *)
 js::NewProxyObject(JSContext *cx, const BaseProxyHandler *handler, HandleValue priv, JSObject *proto_,
                    JSObject *parent_, const ProxyOptions &options)
 {
+    if (options.lazyProto()) {
+        MOZ_ASSERT(!proto_);
+        proto_ = TaggedProto::LazyProto;
+    }
+
     return ProxyObject::New(cx, handler, priv, TaggedProto(proto_), parent_,
                             options);
 }