Bug 761695 - Hoist Xray identification machinery into XrayWrapper, and use it for trait identification. r=peterv

We don't currently have a good way of selecting the traits used by a given Xray
wrapper. This lets us do that.

Note: We add a call to js::UnwrapObject to GetXrayType while hoisting it. When
it was used only in WrapperFactory, this was unnecessary, because |obj| was
always unwrapped. But for our new purposes, it might not be. Aside from that,
there are no changes to the function.

js/xpconnect/wrappers/WrapperFactory.cpp

@@ -292,31 +292,6 @@ GetWrappedNative(JSContext *cx, JSObject *obj)
            : nullptr;
 }
 
-enum XrayType {
-    XrayForDOMObject,
-    XrayForDOMProxyObject,
-    XrayForWrappedNative,
-    NotXray
-};
-
-static XrayType
-GetXrayType(JSObject *obj)
-{
-    if (mozilla::dom::IsDOMObject(obj))
-        return XrayForDOMObject;
-
-    if (mozilla::dom::oldproxybindings::instanceIsProxy(obj))
-        return XrayForDOMProxyObject;
-
-    js::Class* clasp = js::GetObjectClass(obj);
-    if (IS_WRAPPER_CLASS(clasp) || clasp->ext.innerObject) {
-        NS_ASSERTION(clasp->ext.innerObject || IS_WN_WRAPPER_OBJECT(obj),
-                     "We forgot to Morph a slim wrapper!");
-        return XrayForWrappedNative;
-    }
-    return NotXray;
-}
-
 JSObject *
 WrapperFactory::Rewrap(JSContext *cx, JSObject *obj, JSObject *wrappedProto, JSObject *parent,
                        unsigned flags)

js/xpconnect/wrappers/XrayWrapper.cpp

@@ -44,6 +44,25 @@ JSClass HolderClass = {
 
 using namespace XrayUtils;
 
+XrayType
+GetXrayType(JSObject *obj)
+{
+    obj = js::UnwrapObject(obj, /* stopAtOuter = */ false);
+    if (mozilla::dom::IsDOMObject(obj))
+        return XrayForDOMObject;
+
+    if (mozilla::dom::oldproxybindings::instanceIsProxy(obj))
+        return XrayForDOMProxyObject;
+
+    js::Class* clasp = js::GetObjectClass(obj);
+    if (IS_WRAPPER_CLASS(clasp) || clasp->ext.innerObject) {
+        NS_ASSERTION(clasp->ext.innerObject || IS_WN_WRAPPER_OBJECT(obj),
+                     "We forgot to Morph a slim wrapper!");
+        return XrayForWrappedNative;
+    }
+    return NotXray;
+}
+
 ResolvingId::ResolvingId(JSObject *wrapper, jsid id)
     : mId(id),
     mHolder(getHolderObject(wrapper)),
@@ -219,6 +238,21 @@ XPCWrappedNativeXrayTraits XPCWrappedNativeXrayTraits::singleton;
 ProxyXrayTraits ProxyXrayTraits::singleton;
 DOMXrayTraits DOMXrayTraits::singleton;
 
+XrayTraits*
+GetXrayTraits(JSObject *obj)
+{
+    switch (GetXrayType(obj)) {
+      case XrayForDOMObject:
+        return &DOMXrayTraits::singleton;
+      case XrayForDOMProxyObject:
+        return &ProxyXrayTraits::singleton;
+      case XrayForWrappedNative:
+        return &XPCWrappedNativeXrayTraits::singleton;
+      default:
+        return nullptr;
+    }
+}
+
 /*
  * Xray expando handling.
  *

js/xpconnect/wrappers/XrayWrapper.h

@@ -38,10 +38,22 @@ GetNativePropertiesObject(JSContext *cx, JSObject *wrapper);
 
 }
 
+class XrayTraits;
 class XPCWrappedNativeXrayTraits;
 class ProxyXrayTraits;
 class DOMXrayTraits;
 
+
+enum XrayType {
+    XrayForDOMObject,
+    XrayForDOMProxyObject,
+    XrayForWrappedNative,
+    NotXray
+};
+
+XrayType GetXrayType(JSObject *obj);
+XrayTraits* GetXrayTraits(JSObject *obj);
+
 // NB: Base *must* derive from JSProxyHandler
 template <typename Base, typename Traits = XPCWrappedNativeXrayTraits >
 class XrayWrapper : public Base {