diff --git a/dom/base/nsGlobalWindow.cpp b/dom/base/nsGlobalWindow.cpp
index 7e220f455809..214101a3197f 100644
--- a/dom/base/nsGlobalWindow.cpp
+++ b/dom/base/nsGlobalWindow.cpp
@@ -606,7 +606,7 @@ public:
 JSString *
 nsOuterWindowProxy::obj_toString(JSContext *cx, JSObject *proxy)
 {
-    JS_ASSERT(js::IsProxy(proxy));
+    MOZ_ASSERT(js::IsProxy(proxy));
 
     return JS_NewStringCopyZ(cx, "[object Window]");
 }
@@ -626,8 +626,29 @@ nsOuterWindowProxy::finalize(JSFreeOp *fop, JSObject *proxy)
 nsOuterWindowProxy
 nsOuterWindowProxy::singleton;
 
+class nsChromeOuterWindowProxy : public nsOuterWindowProxy
+{
+public:
+  nsChromeOuterWindowProxy() : nsOuterWindowProxy() {}
+
+  virtual JSString *obj_toString(JSContext *cx, JSObject *wrapper);
+
+  static nsChromeOuterWindowProxy singleton;
+};
+
+JSString *
+nsChromeOuterWindowProxy::obj_toString(JSContext *cx, JSObject *proxy)
+{
+    MOZ_ASSERT(js::IsProxy(proxy));
+
+    return JS_NewStringCopyZ(cx, "[object ChromeWindow]");
+}
+
+nsChromeOuterWindowProxy
+nsChromeOuterWindowProxy::singleton;
+
 static JSObject*
-NewOuterWindowProxy(JSContext *cx, JSObject *parent)
+NewOuterWindowProxy(JSContext *cx, JSObject *parent, bool isChrome)
 {
   JSAutoCompartment ac(cx, parent);
   JSObject *proto;
@@ -635,7 +656,9 @@ NewOuterWindowProxy(JSContext *cx, JSObject *parent)
     return nullptr;
 
   JSObject *obj = js::Wrapper::New(cx, parent, proto, parent,
-                                   &nsOuterWindowProxy::singleton);
+                                   isChrome ? &nsChromeOuterWindowProxy::singleton
+                                            : &nsOuterWindowProxy::singleton);
+
   NS_ASSERTION(js::GetObjectClass(obj)->ext.innerObject, "bad class");
   return obj;
 }
@@ -1673,7 +1696,8 @@ nsGlobalWindow::CreateOuterObject(nsGlobalWindow* aNewInner)
 {
   JSContext* cx = mContext->GetNativeContext();
 
-  if (IsChromeWindow()) {
+  bool isChrome = IsChromeWindow();
+  if (isChrome) {
     // Always enable E4X for XUL and other chrome content -- there is no
     // need to preserve the <!-- script hiding hack from JS-in-HTML daze
     // (introduced in 1995 for graceful script degradation in Netscape 1,
@@ -1681,7 +1705,8 @@ nsGlobalWindow::CreateOuterObject(nsGlobalWindow* aNewInner)
     JS_SetOptions(cx, JS_GetOptions(cx) | JSOPTION_MOAR_XML);
   }
 
-  JSObject* outer = NewOuterWindowProxy(cx, aNewInner->FastGetGlobalJSObject());
+  JSObject* outer = NewOuterWindowProxy(cx, aNewInner->FastGetGlobalJSObject(),
+                                        isChrome);
   if (!outer) {
     return NS_ERROR_FAILURE;
   }
@@ -1987,7 +2012,8 @@ nsGlobalWindow::SetNewDocument(nsIDocument* aDocument,
       mJSObject = mContext->GetNativeGlobal();
       SetWrapper(mJSObject);
     } else {
-      JSObject *outerObject = NewOuterWindowProxy(cx, xpc_UnmarkGrayObject(newInnerWindow->mJSObject));
+      JSObject *outerObject = NewOuterWindowProxy(cx, xpc_UnmarkGrayObject(newInnerWindow->mJSObject),
+                                                  thisChrome);
       if (!outerObject) {
         NS_ERROR("out of memory");
         return NS_ERROR_FAILURE;
diff --git a/js/xpconnect/src/XPCWrappedNativeJSOps.cpp b/js/xpconnect/src/XPCWrappedNativeJSOps.cpp
index 458b6d5f7cdc..8c1a53d13c31 100644
--- a/js/xpconnect/src/XPCWrappedNativeJSOps.cpp
+++ b/js/xpconnect/src/XPCWrappedNativeJSOps.cpp
@@ -11,7 +11,9 @@
 #include "XPCWrapper.h"
 #include "nsWrapperCacheInlines.h"
 #include "mozilla/dom/BindingUtils.h"
+#include "mozilla/Preferences.h"
 
+using namespace mozilla;
 /***************************************************************************/
 
 // All of the exceptions thrown into JS from this file go through here.
@@ -254,8 +256,25 @@ DefinePropertyIfFound(XPCCallContext& ccx,
     if (!found) {
         if (reflectToStringAndToSource) {
             JSNative call;
+            uint32_t flags = 0;
 
-            if (id == rt->GetStringID(XPCJSRuntime::IDX_TO_STRING)) {
+            if (scriptableInfo) {
+                nsCOMPtr<nsIClassInfo> classInfo = do_QueryInterface(
+                    scriptableInfo->GetCallback());
+
+                if (classInfo) {
+                    nsresult rv = classInfo->GetFlags(&flags);
+                    if (NS_FAILED(rv))
+                        return Throw(rv, ccx);
+                }
+            }
+
+            bool overwriteToString = !(flags & nsIClassInfo::DOM_OBJECT)
+                || Preferences::GetBool("dom.XPCToStringForDOMClasses", false);
+
+            if(id == rt->GetStringID(XPCJSRuntime::IDX_TO_STRING)
+                && overwriteToString)
+            {
                 call = XPC_WN_Shared_ToString;
                 name = rt->GetStringName(XPCJSRuntime::IDX_TO_STRING);
                 id   = rt->GetStringID(XPCJSRuntime::IDX_TO_STRING);