Add m-esr52 at 52.6.0

1 files changed, 2325 insertions, 0 deletions

diff --git a/js/xpconnect/src/XPCWrappedNative.cpp b/js/xpconnect/src/XPCWrappedNative.cpp
new file mode 100644
index 000000000..acf92f3c3
--- /dev/null
+++ b/js/xpconnect/src/XPCWrappedNative.cpp
@@ -0,0 +1,2325 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/* vim: set ts=8 sts=4 et sw=4 tw=99: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* Wrapper object for reflecting native xpcom objects into JavaScript. */
+
+#include "xpcprivate.h"
+#include "mozilla/jsipc/CrossProcessObjectWrappers.h"
+#include "nsWrapperCacheInlines.h"
+#include "XPCLog.h"
+#include "jsprf.h"
+#include "jsfriendapi.h"
+#include "AccessCheck.h"
+#include "WrapperFactory.h"
+#include "XrayWrapper.h"
+
+#include "nsContentUtils.h"
+#include "nsCycleCollectionNoteRootCallback.h"
+
+#include <stdint.h>
+#include "mozilla/DeferredFinalize.h"
+#include "mozilla/Likely.h"
+#include "mozilla/Unused.h"
+#include "mozilla/Sprintf.h"
+#include "mozilla/dom/BindingUtils.h"
+#include <algorithm>
+
+using namespace xpc;
+using namespace mozilla;
+using namespace mozilla::dom;
+using namespace JS;
+
+/***************************************************************************/
+
+NS_IMPL_CYCLE_COLLECTION_CLASS(XPCWrappedNative)
+
+// No need to unlink the JS objects: if the XPCWrappedNative is cycle
+// collected then its mFlatJSObject will be cycle collected too and
+// finalization of the mFlatJSObject will unlink the JS objects (see
+// XPC_WN_NoHelper_Finalize and FlatJSObjectFinalized).
+NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(XPCWrappedNative)
+    tmp->ExpireWrapper();
+NS_IMPL_CYCLE_COLLECTION_UNLINK_END
+
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN_INTERNAL(XPCWrappedNative)
+    if (!tmp->IsValid())
+        return NS_OK;
+
+    if (MOZ_UNLIKELY(cb.WantDebugInfo())) {
+        char name[72];
+        XPCNativeScriptableInfo* si = tmp->GetScriptableInfo();
+        if (si)
+            SprintfLiteral(name, "XPCWrappedNative (%s)", si->GetJSClass()->name);
+        else
+            SprintfLiteral(name, "XPCWrappedNative");
+
+        cb.DescribeRefCountedNode(tmp->mRefCnt.get(), name);
+    } else {
+        NS_IMPL_CYCLE_COLLECTION_DESCRIBE(XPCWrappedNative, tmp->mRefCnt.get())
+    }
+
+    if (tmp->HasExternalReference()) {
+
+        // If our refcount is > 1, our reference to the flat JS object is
+        // considered "strong", and we're going to traverse it.
+        //
+        // If our refcount is <= 1, our reference to the flat JS object is
+        // considered "weak", and we're *not* going to traverse it.
+        //
+        // This reasoning is in line with the slightly confusing lifecycle rules
+        // for XPCWrappedNatives, described in a larger comment below and also
+        // on our wiki at http://wiki.mozilla.org/XPConnect_object_wrapping
+
+        JSObject* obj = tmp->GetFlatJSObjectPreserveColor();
+        NS_CYCLE_COLLECTION_NOTE_EDGE_NAME(cb, "mFlatJSObject");
+        cb.NoteJSChild(JS::GCCellPtr(obj));
+    }
+
+    // XPCWrappedNative keeps its native object alive.
+    NS_CYCLE_COLLECTION_NOTE_EDGE_NAME(cb, "mIdentity");
+    cb.NoteXPCOMChild(tmp->GetIdentityObject());
+
+    tmp->NoteTearoffs(cb);
+
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
+
+void
+XPCWrappedNative::Suspect(nsCycleCollectionNoteRootCallback& cb)
+{
+    if (!IsValid() || IsWrapperExpired())
+        return;
+
+    MOZ_ASSERT(NS_IsMainThread(),
+               "Suspecting wrapped natives from non-main thread");
+
+    // Only record objects that might be part of a cycle as roots, unless
+    // the callback wants all traces (a debug feature). Do this even if
+    // the XPCWN doesn't own the JS reflector object in case the reflector
+    // keeps alive other C++ things. This is safe because if the reflector
+    // had died the reference from the XPCWN to it would have been cleared.
+    JSObject* obj = GetFlatJSObjectPreserveColor();
+    if (JS::ObjectIsMarkedGray(obj) || cb.WantAllTraces())
+        cb.NoteJSRoot(obj);
+}
+
+void
+XPCWrappedNative::NoteTearoffs(nsCycleCollectionTraversalCallback& cb)
+{
+    // Tearoffs hold their native object alive. If their JS object hasn't been
+    // finalized yet we'll note the edge between the JS object and the native
+    // (see nsXPConnect::Traverse), but if their JS object has been finalized
+    // then the tearoff is only reachable through the XPCWrappedNative, so we
+    // record an edge here.
+    for (XPCWrappedNativeTearOff* to = &mFirstTearOff; to; to = to->GetNextTearOff()) {
+        JSObject* jso = to->GetJSObjectPreserveColor();
+        if (!jso) {
+            NS_CYCLE_COLLECTION_NOTE_EDGE_NAME(cb, "tearoff's mNative");
+            cb.NoteXPCOMChild(to->GetNative());
+        }
+    }
+}
+
+#ifdef XPC_CHECK_CLASSINFO_CLAIMS
+static void DEBUG_CheckClassInfoClaims(XPCWrappedNative* wrapper);
+#else
+#define DEBUG_CheckClassInfoClaims(wrapper) ((void)0)
+#endif
+
+/***************************************************************************/
+static nsresult
+FinishCreate(XPCWrappedNativeScope* Scope,
+             XPCNativeInterface* Interface,
+             nsWrapperCache* cache,
+             XPCWrappedNative* inWrapper,
+             XPCWrappedNative** resultWrapper);
+
+// static
+//
+// This method handles the special case of wrapping a new global object.
+//
+// The normal code path for wrapping natives goes through
+// XPCConvert::NativeInterface2JSObject, XPCWrappedNative::GetNewOrUsed,
+// and finally into XPCWrappedNative::Init. Unfortunately, this path assumes
+// very early on that we have an XPCWrappedNativeScope and corresponding global
+// JS object, which are the very things we need to create here. So we special-
+// case the logic and do some things in a different order.
+nsresult
+XPCWrappedNative::WrapNewGlobal(xpcObjectHelper& nativeHelper,
+                                nsIPrincipal* principal,
+                                bool initStandardClasses,
+                                JS::CompartmentOptions& aOptions,
+                                XPCWrappedNative** wrappedGlobal)
+{
+    AutoJSContext cx;
+    nsISupports* identity = nativeHelper.GetCanonical();
+
+    // The object should specify that it's meant to be global.
+    MOZ_ASSERT(nativeHelper.GetScriptableFlags() & nsIXPCScriptable::IS_GLOBAL_OBJECT);
+
+    // We shouldn't be reusing globals.
+    MOZ_ASSERT(!nativeHelper.GetWrapperCache() ||
+               !nativeHelper.GetWrapperCache()->GetWrapperPreserveColor());
+
+    // Put together the ScriptableCreateInfo...
+    XPCNativeScriptableCreateInfo sciProto;
+    XPCNativeScriptableCreateInfo sciMaybe;
+    const XPCNativeScriptableCreateInfo& sciWrapper =
+        GatherScriptableCreateInfo(identity, nativeHelper.GetClassInfo(),
+                                   sciProto, sciMaybe);
+
+    // ...and then ScriptableInfo. We need all this stuff now because it's going
+    // to tell us the JSClass of the object we're going to create.
+    XPCNativeScriptableInfo* si = XPCNativeScriptableInfo::Construct(&sciWrapper);
+    MOZ_ASSERT(si);
+
+    // Finally, we get to the JSClass.
+    const JSClass* clasp = si->GetJSClass();
+    MOZ_ASSERT(clasp->flags & JSCLASS_IS_GLOBAL);
+
+    // Create the global.
+    aOptions.creationOptions().setTrace(XPCWrappedNative::Trace);
+    if (xpc::SharedMemoryEnabled())
+        aOptions.creationOptions().setSharedMemoryAndAtomicsEnabled(true);
+    RootedObject global(cx, xpc::CreateGlobalObject(cx, clasp, principal, aOptions));
+    if (!global)
+        return NS_ERROR_FAILURE;
+    XPCWrappedNativeScope* scope = CompartmentPrivate::Get(global)->scope;
+
+    // Immediately enter the global's compartment, so that everything else we
+    // create ends up there.
+    JSAutoCompartment ac(cx, global);
+
+    // If requested, initialize the standard classes on the global.
+    if (initStandardClasses && ! JS_InitStandardClasses(cx, global))
+        return NS_ERROR_FAILURE;
+
+    // Make a proto.
+    XPCWrappedNativeProto* proto =
+        XPCWrappedNativeProto::GetNewOrUsed(scope,
+                                            nativeHelper.GetClassInfo(), &sciProto,
+                                            /* callPostCreatePrototype = */ false);
+    if (!proto)
+        return NS_ERROR_FAILURE;
+
+    // Set up the prototype on the global.
+    MOZ_ASSERT(proto->GetJSProtoObject());
+    RootedObject protoObj(cx, proto->GetJSProtoObject());
+    bool success = JS_SplicePrototype(cx, global, protoObj);
+    if (!success)
+        return NS_ERROR_FAILURE;
+
+    // Construct the wrapper, which takes over the strong reference to the
+    // native object.
+    RefPtr<XPCWrappedNative> wrapper =
+        new XPCWrappedNative(nativeHelper.forgetCanonical(), proto);
+
+    //
+    // We don't call ::Init() on this wrapper, because our setup requirements
+    // are different for globals. We do our setup inline here, instead.
+    //
+
+    // Share mScriptableInfo with the proto.
+    //
+    // This is probably more trouble than it's worth, since we've already
+    // created an XPCNativeScriptableInfo for ourselves. Nevertheless, this is
+    // what ::Init() does, and we want to be as consistent as possible with
+    // that code.
+    XPCNativeScriptableInfo* siProto = proto->GetScriptableInfo();
+    if (siProto && siProto->GetCallback() == sciWrapper.GetCallback()) {
+        wrapper->mScriptableInfo = siProto;
+        // XPCNativeScriptableInfo uses manual memory management. If we're
+        // switching over to that of the proto, we need to destroy the one
+        // we've allocated.
+        delete si;
+        si = nullptr;
+    } else {
+        wrapper->mScriptableInfo = si;
+    }
+
+    // Set the JS object to the global we already created.
+    wrapper->mFlatJSObject = global;
+    wrapper->mFlatJSObject.setFlags(FLAT_JS_OBJECT_VALID);
+
+    // Set the private to the XPCWrappedNative.
+    JS_SetPrivate(global, wrapper);
+
+    // There are dire comments elsewhere in the code about how a GC can
+    // happen somewhere after wrapper initialization but before the wrapper is
+    // added to the hashtable in FinishCreate(). It's not clear if that can
+    // happen here, but let's just be safe for now.
+    AutoMarkingWrappedNativePtr wrapperMarker(cx, wrapper);
+
+    // Call the common Init finish routine. This mainly just does an AddRef
+    // on behalf of XPConnect (the corresponding Release is in the finalizer
+    // hook), but it does some other miscellaneous things too, so we don't
+    // inline it.
+    success = wrapper->FinishInit();
+    MOZ_ASSERT(success);
+
+    // Go through some extra work to find the tearoff. This is kind of silly
+    // on a conceptual level: the point of tearoffs is to cache the results
+    // of QI-ing mIdentity to different interfaces, and we don't need that
+    // since we're dealing with nsISupports. But lots of code expects tearoffs
+    // to exist for everything, so we just follow along.
+    RefPtr<XPCNativeInterface> iface = XPCNativeInterface::GetNewOrUsed(&NS_GET_IID(nsISupports));
+    MOZ_ASSERT(iface);
+    nsresult status;
+    success = wrapper->FindTearOff(iface, false, &status);
+    if (!success)
+        return status;
+
+    // Call the common creation finish routine. This does all of the bookkeeping
+    // like inserting the wrapper into the wrapper map and setting up the wrapper
+    // cache.
+    nsresult rv = FinishCreate(scope, iface, nativeHelper.GetWrapperCache(),
+                               wrapper, wrappedGlobal);
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    return NS_OK;
+}
+
+// static
+nsresult
+XPCWrappedNative::GetNewOrUsed(xpcObjectHelper& helper,
+                               XPCWrappedNativeScope* Scope,
+                               XPCNativeInterface* Interface,
+                               XPCWrappedNative** resultWrapper)
+{
+    MOZ_ASSERT(Interface);
+    AutoJSContext cx;
+    nsWrapperCache* cache = helper.GetWrapperCache();
+
+    MOZ_ASSERT(!cache || !cache->GetWrapperPreserveColor(),
+               "We assume the caller already checked if it could get the "
+               "wrapper from the cache.");
+
+    nsresult rv;
+
+    MOZ_ASSERT(!Scope->GetContext()->GCIsRunning(),
+               "XPCWrappedNative::GetNewOrUsed called during GC");
+
+    nsISupports* identity = helper.GetCanonical();
+
+    if (!identity) {
+        NS_ERROR("This XPCOM object fails in QueryInterface to nsISupports!");
+        return NS_ERROR_FAILURE;
+    }
+
+    RefPtr<XPCWrappedNative> wrapper;
+
+    Native2WrappedNativeMap* map = Scope->GetWrappedNativeMap();
+    // Some things are nsWrapperCache subclasses but never use the cache, so go
+    // ahead and check our map even if we have a cache and it has no existing
+    // wrapper: we might have an XPCWrappedNative anyway.
+    wrapper = map->Find(identity);
+
+    if (wrapper) {
+        if (!wrapper->FindTearOff(Interface, false, &rv)) {
+            MOZ_ASSERT(NS_FAILED(rv), "returning NS_OK on failure");
+            return rv;
+        }
+        wrapper.forget(resultWrapper);
+        return NS_OK;
+    }
+
+    // There is a chance that the object wants to have the self-same JSObject
+    // reflection regardless of the scope into which we are reflecting it.
+    // Many DOM objects require this. The scriptable helper specifies this
+    // in preCreate by indicating a 'parent' of a particular scope.
+    //
+    // To handle this we need to get the scriptable helper early and ask it.
+    // It is possible that we will then end up forwarding this entire call
+    // to this same function but with a different scope.
+
+    // If we are making a wrapper for an nsIClassInfo singleton then
+    // We *don't* want to have it use the prototype meant for instances
+    // of that class.
+    uint32_t classInfoFlags;
+    bool isClassInfoSingleton = helper.GetClassInfo() == helper.Object() &&
+                                NS_SUCCEEDED(helper.GetClassInfo()
+                                                   ->GetFlags(&classInfoFlags)) &&
+                                (classInfoFlags & nsIClassInfo::SINGLETON_CLASSINFO);
+
+    nsIClassInfo* info = helper.GetClassInfo();
+
+    XPCNativeScriptableCreateInfo sciProto;
+    XPCNativeScriptableCreateInfo sci;
+
+    // Gather scriptable create info if we are wrapping something
+    // other than an nsIClassInfo object. We need to not do this for
+    // nsIClassInfo objects because often nsIClassInfo implementations
+    // are also nsIXPCScriptable helper implementations, but the helper
+    // code is obviously intended for the implementation of the class
+    // described by the nsIClassInfo, not for the class info object
+    // itself.
+    const XPCNativeScriptableCreateInfo& sciWrapper =
+        isClassInfoSingleton ? sci :
+        GatherScriptableCreateInfo(identity, info, sciProto, sci);
+
+    RootedObject parent(cx, Scope->GetGlobalJSObject());
+
+    mozilla::Maybe<JSAutoCompartment> ac;
+
+    if (sciWrapper.GetFlags().WantPreCreate()) {
+        RootedObject plannedParent(cx, parent);
+        nsresult rv = sciWrapper.GetCallback()->PreCreate(identity, cx,
+                                                          parent, parent.address());
+        if (NS_FAILED(rv))
+            return rv;
+        rv = NS_OK;
+
+        MOZ_ASSERT(!xpc::WrapperFactory::IsXrayWrapper(parent),
+                   "Xray wrapper being used to parent XPCWrappedNative?");
+
+        MOZ_ASSERT(js::GetGlobalForObjectCrossCompartment(parent) == parent,
+                   "Non-global being used to parent XPCWrappedNative?");
+
+        ac.emplace(static_cast<JSContext*>(cx), parent);
+
+        if (parent != plannedParent) {
+            XPCWrappedNativeScope* betterScope = ObjectScope(parent);
+            MOZ_ASSERT(betterScope != Scope,
+                       "How can we have the same scope for two different globals?");
+            return GetNewOrUsed(helper, betterScope, Interface, resultWrapper);
+        }
+
+        // Take the performance hit of checking the hashtable again in case
+        // the preCreate call caused the wrapper to get created through some
+        // interesting path (the DOM code tends to make this happen sometimes).
+
+        if (cache) {
+            RootedObject cached(cx, cache->GetWrapper());
+            if (cached)
+                wrapper = XPCWrappedNative::Get(cached);
+        } else {
+            wrapper = map->Find(identity);
+        }
+
+        if (wrapper) {
+            if (wrapper->FindTearOff(Interface, false, &rv)) {
+                MOZ_ASSERT(NS_FAILED(rv), "returning NS_OK on failure");
+                return rv;
+            }
+            wrapper.forget(resultWrapper);
+            return NS_OK;
+        }
+    } else {
+        ac.emplace(static_cast<JSContext*>(cx), parent);
+    }
+
+    AutoMarkingWrappedNativeProtoPtr proto(cx);
+
+    // If there is ClassInfo (and we are not building a wrapper for the
+    // nsIClassInfo interface) then we use a wrapper that needs a prototype.
+
+    // Note that the security check happens inside FindTearOff - after the
+    // wrapper is actually created, but before JS code can see it.
+
+    if (info && !isClassInfoSingleton) {
+        proto = XPCWrappedNativeProto::GetNewOrUsed(Scope, info, &sciProto);
+        if (!proto)
+            return NS_ERROR_FAILURE;
+
+        wrapper = new XPCWrappedNative(helper.forgetCanonical(), proto);
+    } else {
+        RefPtr<XPCNativeInterface> iface = Interface;
+        if (!iface)
+            iface = XPCNativeInterface::GetISupports();
+
+        XPCNativeSetKey key(iface);
+        RefPtr<XPCNativeSet> set =
+            XPCNativeSet::GetNewOrUsed(&key);
+
+        if (!set)
+            return NS_ERROR_FAILURE;
+
+        wrapper = new XPCWrappedNative(helper.forgetCanonical(), Scope,
+                                       set.forget());
+    }
+
+    MOZ_ASSERT(!xpc::WrapperFactory::IsXrayWrapper(parent),
+               "Xray wrapper being used to parent XPCWrappedNative?");
+
+    // We use an AutoMarkingPtr here because it is possible for JS gc to happen
+    // after we have Init'd the wrapper but *before* we add it to the hashtable.
+    // This would cause the mSet to get collected and we'd later crash. I've
+    // *seen* this happen.
+    AutoMarkingWrappedNativePtr wrapperMarker(cx, wrapper);
+
+    if (!wrapper->Init(&sciWrapper))
+        return NS_ERROR_FAILURE;
+
+    if (!wrapper->FindTearOff(Interface, false, &rv)) {
+        MOZ_ASSERT(NS_FAILED(rv), "returning NS_OK on failure");
+        return rv;
+    }
+
+    return FinishCreate(Scope, Interface, cache, wrapper, resultWrapper);
+}
+
+static nsresult
+FinishCreate(XPCWrappedNativeScope* Scope,
+             XPCNativeInterface* Interface,
+             nsWrapperCache* cache,
+             XPCWrappedNative* inWrapper,
+             XPCWrappedNative** resultWrapper)
+{
+    AutoJSContext cx;
+    MOZ_ASSERT(inWrapper);
+
+    Native2WrappedNativeMap* map = Scope->GetWrappedNativeMap();
+
+    RefPtr<XPCWrappedNative> wrapper;
+    // Deal with the case where the wrapper got created as a side effect
+    // of one of our calls out of this code. Add() returns the (possibly
+    // pre-existing) wrapper that ultimately ends up in the map, which is
+    // what we want.
+    wrapper = map->Add(inWrapper);
+    if (!wrapper)
+        return NS_ERROR_FAILURE;
+
+    if (wrapper == inWrapper) {
+        JSObject* flat = wrapper->GetFlatJSObject();
+        MOZ_ASSERT(!cache || !cache->GetWrapperPreserveColor() ||
+                   flat == cache->GetWrapperPreserveColor(),
+                   "This object has a cached wrapper that's different from "
+                   "the JSObject held by its native wrapper?");
+
+        if (cache && !cache->GetWrapperPreserveColor())
+            cache->SetWrapper(flat);
+    }
+
+    DEBUG_CheckClassInfoClaims(wrapper);
+    wrapper.forget(resultWrapper);
+    return NS_OK;
+}
+
+// static
+nsresult
+XPCWrappedNative::GetUsedOnly(nsISupports* Object,
+                              XPCWrappedNativeScope* Scope,
+                              XPCNativeInterface* Interface,
+                              XPCWrappedNative** resultWrapper)
+{
+    AutoJSContext cx;
+    MOZ_ASSERT(Object, "XPCWrappedNative::GetUsedOnly was called with a null Object");
+    MOZ_ASSERT(Interface);
+
+    RefPtr<XPCWrappedNative> wrapper;
+    nsWrapperCache* cache = nullptr;
+    CallQueryInterface(Object, &cache);
+    if (cache) {
+        RootedObject flat(cx, cache->GetWrapper());
+        if (!flat) {
+            *resultWrapper = nullptr;
+            return NS_OK;
+        }
+        wrapper = XPCWrappedNative::Get(flat);
+    } else {
+        nsCOMPtr<nsISupports> identity = do_QueryInterface(Object);
+
+        if (!identity) {
+            NS_ERROR("This XPCOM object fails in QueryInterface to nsISupports!");
+            return NS_ERROR_FAILURE;
+        }
+
+        Native2WrappedNativeMap* map = Scope->GetWrappedNativeMap();
+
+        wrapper = map->Find(identity);
+        if (!wrapper) {
+            *resultWrapper = nullptr;
+            return NS_OK;
+        }
+    }
+
+    nsresult rv;
+    if (!wrapper->FindTearOff(Interface, false, &rv)) {
+        MOZ_ASSERT(NS_FAILED(rv), "returning NS_OK on failure");
+        return rv;
+    }
+
+    wrapper.forget(resultWrapper);
+    return NS_OK;
+}
+
+// This ctor is used if this object will have a proto.
+XPCWrappedNative::XPCWrappedNative(already_AddRefed<nsISupports>&& aIdentity,
+                                   XPCWrappedNativeProto* aProto)
+    : mMaybeProto(aProto),
+      mSet(aProto->GetSet()),
+      mScriptableInfo(nullptr)
+{
+    MOZ_ASSERT(NS_IsMainThread());
+
+    mIdentity = aIdentity;
+    mFlatJSObject.setFlags(FLAT_JS_OBJECT_VALID);
+
+    MOZ_ASSERT(mMaybeProto, "bad ctor param");
+    MOZ_ASSERT(mSet, "bad ctor param");
+}
+
+// This ctor is used if this object will NOT have a proto.
+XPCWrappedNative::XPCWrappedNative(already_AddRefed<nsISupports>&& aIdentity,
+                                   XPCWrappedNativeScope* aScope,
+                                   already_AddRefed<XPCNativeSet>&& aSet)
+
+    : mMaybeScope(TagScope(aScope)),
+      mSet(aSet),
+      mScriptableInfo(nullptr)
+{
+    MOZ_ASSERT(NS_IsMainThread());
+
+    mIdentity = aIdentity;
+    mFlatJSObject.setFlags(FLAT_JS_OBJECT_VALID);
+
+    MOZ_ASSERT(aScope, "bad ctor param");
+    MOZ_ASSERT(mSet, "bad ctor param");
+}
+
+XPCWrappedNative::~XPCWrappedNative()
+{
+    Destroy();
+}
+
+void
+XPCWrappedNative::Destroy()
+{
+    XPCWrappedNativeProto* proto = GetProto();
+
+    if (mScriptableInfo &&
+        (!HasProto() ||
+         (proto && proto->GetScriptableInfo() != mScriptableInfo))) {
+        delete mScriptableInfo;
+        mScriptableInfo = nullptr;
+    }
+
+    XPCWrappedNativeScope* scope = GetScope();
+    if (scope) {
+        Native2WrappedNativeMap* map = scope->GetWrappedNativeMap();
+
+        // Post-1.9 we should not remove this wrapper from the map if it is
+        // uninitialized.
+        map->Remove(this);
+    }
+
+    if (mIdentity) {
+        XPCJSContext* cx = GetContext();
+        if (cx && cx->GetDoingFinalization()) {
+            DeferredFinalize(mIdentity.forget().take());
+        } else {
+            mIdentity = nullptr;
+        }
+    }
+
+    mMaybeScope = nullptr;
+}
+
+void
+XPCWrappedNative::UpdateScriptableInfo(XPCNativeScriptableInfo* si)
+{
+    MOZ_ASSERT(mScriptableInfo, "UpdateScriptableInfo expects an existing scriptable info");
+    mScriptableInfo = si;
+}
+
+void
+XPCWrappedNative::SetProto(XPCWrappedNativeProto* p)
+{
+    MOZ_ASSERT(!IsWrapperExpired(), "bad ptr!");
+
+    MOZ_ASSERT(HasProto());
+
+    // Write barrier for incremental GC.
+    JSContext* cx = GetContext()->Context();
+    GetProto()->WriteBarrierPre(cx);
+
+    mMaybeProto = p;
+}
+
+// This is factored out so that it can be called publicly
+// static
+void
+XPCWrappedNative::GatherProtoScriptableCreateInfo(nsIClassInfo* classInfo,
+                                                  XPCNativeScriptableCreateInfo& sciProto)
+{
+    MOZ_ASSERT(classInfo, "bad param");
+    MOZ_ASSERT(!sciProto.GetCallback(), "bad param");
+
+    nsXPCClassInfo* classInfoHelper = nullptr;
+    CallQueryInterface(classInfo, &classInfoHelper);
+    if (classInfoHelper) {
+        nsCOMPtr<nsIXPCScriptable> helper =
+          dont_AddRef(static_cast<nsIXPCScriptable*>(classInfoHelper));
+        uint32_t flags = classInfoHelper->GetScriptableFlags();
+        sciProto.SetCallback(helper.forget());
+        sciProto.SetFlags(XPCNativeScriptableFlags(flags));
+
+        return;
+    }
+
+    nsCOMPtr<nsIXPCScriptable> helper;
+    nsresult rv = classInfo->GetScriptableHelper(getter_AddRefs(helper));
+    if (NS_SUCCEEDED(rv) && helper) {
+        uint32_t flags = helper->GetScriptableFlags();
+        sciProto.SetCallback(helper.forget());
+        sciProto.SetFlags(XPCNativeScriptableFlags(flags));
+    }
+}
+
+// static
+const XPCNativeScriptableCreateInfo&
+XPCWrappedNative::GatherScriptableCreateInfo(nsISupports* obj,
+                                             nsIClassInfo* classInfo,
+                                             XPCNativeScriptableCreateInfo& sciProto,
+                                             XPCNativeScriptableCreateInfo& sciWrapper)
+{
+    MOZ_ASSERT(!sciWrapper.GetCallback(), "bad param");
+
+    // Get the class scriptable helper (if present)
+    if (classInfo) {
+        GatherProtoScriptableCreateInfo(classInfo, sciProto);
+
+        if (sciProto.GetFlags().DontAskInstanceForScriptable())
+            return sciProto;
+    }
+
+    // Do the same for the wrapper specific scriptable
+    nsCOMPtr<nsIXPCScriptable> helper(do_QueryInterface(obj));
+    if (helper) {
+        uint32_t flags = helper->GetScriptableFlags();
+        sciWrapper.SetCallback(helper.forget());
+        sciWrapper.SetFlags(XPCNativeScriptableFlags(flags));
+
+        // A whole series of assertions to catch bad uses of scriptable flags on
+        // the siWrapper...
+
+        MOZ_ASSERT(!(sciWrapper.GetFlags().WantPreCreate() &&
+                     !sciProto.GetFlags().WantPreCreate()),
+                   "Can't set WANT_PRECREATE on an instance scriptable "
+                   "without also setting it on the class scriptable");
+
+        MOZ_ASSERT(!(sciWrapper.GetFlags().DontEnumQueryInterface() &&
+                     !sciProto.GetFlags().DontEnumQueryInterface() &&
+                     sciProto.GetCallback()),
+                   "Can't set DONT_ENUM_QUERY_INTERFACE on an instance scriptable "
+                   "without also setting it on the class scriptable (if present and shared)");
+
+        MOZ_ASSERT(!(sciWrapper.GetFlags().DontAskInstanceForScriptable() &&
+                     !sciProto.GetFlags().DontAskInstanceForScriptable()),
+                   "Can't set DONT_ASK_INSTANCE_FOR_SCRIPTABLE on an instance scriptable "
+                   "without also setting it on the class scriptable");
+
+        MOZ_ASSERT(!(sciWrapper.GetFlags().ClassInfoInterfacesOnly() &&
+                     !sciProto.GetFlags().ClassInfoInterfacesOnly() &&
+                     sciProto.GetCallback()),
+                   "Can't set CLASSINFO_INTERFACES_ONLY on an instance scriptable "
+                   "without also setting it on the class scriptable (if present and shared)");
+
+        MOZ_ASSERT(!(sciWrapper.GetFlags().AllowPropModsDuringResolve() &&
+                     !sciProto.GetFlags().AllowPropModsDuringResolve() &&
+                     sciProto.GetCallback()),
+                   "Can't set ALLOW_PROP_MODS_DURING_RESOLVE on an instance scriptable "
+                   "without also setting it on the class scriptable (if present and shared)");
+
+        MOZ_ASSERT(!(sciWrapper.GetFlags().AllowPropModsToPrototype() &&
+                     !sciProto.GetFlags().AllowPropModsToPrototype() &&
+                     sciProto.GetCallback()),
+                   "Can't set ALLOW_PROP_MODS_TO_PROTOTYPE on an instance scriptable "
+                   "without also setting it on the class scriptable (if present and shared)");
+
+        return sciWrapper;
+    }
+
+    return sciProto;
+}
+
+bool
+XPCWrappedNative::Init(const XPCNativeScriptableCreateInfo* sci)
+{
+    AutoJSContext cx;
+    // setup our scriptable info...
+
+    if (sci->GetCallback()) {
+        if (HasProto()) {
+            XPCNativeScriptableInfo* siProto = GetProto()->GetScriptableInfo();
+            if (siProto && siProto->GetCallback() == sci->GetCallback())
+                mScriptableInfo = siProto;
+        }
+        if (!mScriptableInfo) {
+            mScriptableInfo = XPCNativeScriptableInfo::Construct(sci);
+
+            if (!mScriptableInfo)
+                return false;
+        }
+    }
+    XPCNativeScriptableInfo* si = mScriptableInfo;
+
+    // create our flatJSObject
+
+    const JSClass* jsclazz = si ? si->GetJSClass() : Jsvalify(&XPC_WN_NoHelper_JSClass);
+
+    // We should have the global jsclass flag if and only if we're a global.
+    MOZ_ASSERT_IF(si, !!si->GetFlags().IsGlobalObject() == !!(jsclazz->flags & JSCLASS_IS_GLOBAL));
+
+    MOZ_ASSERT(jsclazz &&
+               jsclazz->name &&
+               jsclazz->flags &&
+               jsclazz->getResolve() &&
+               jsclazz->hasFinalize(), "bad class");
+
+    // XXXbz JS_GetObjectPrototype wants an object, even though it then asserts
+    // that this object is same-compartment with cx, which means it could just
+    // use the cx global...
+    RootedObject global(cx, CurrentGlobalOrNull(cx));
+    RootedObject protoJSObject(cx, HasProto() ?
+                                   GetProto()->GetJSProtoObject() :
+                                   JS_GetObjectPrototype(cx, global));
+    if (!protoJSObject) {
+        return false;
+    }
+
+    mFlatJSObject = JS_NewObjectWithGivenProto(cx, jsclazz, protoJSObject);
+    if (!mFlatJSObject) {
+        mFlatJSObject.unsetFlags(FLAT_JS_OBJECT_VALID);
+        return false;
+    }
+
+    mFlatJSObject.setFlags(FLAT_JS_OBJECT_VALID);
+    JS_SetPrivate(mFlatJSObject, this);
+
+    return FinishInit();
+}
+
+bool
+XPCWrappedNative::FinishInit()
+{
+    AutoJSContext cx;
+
+    // This reference will be released when mFlatJSObject is finalized.
+    // Since this reference will push the refcount to 2 it will also root
+    // mFlatJSObject;
+    MOZ_ASSERT(1 == mRefCnt, "unexpected refcount value");
+    NS_ADDREF(this);
+
+    // A hack for bug 517665, increase the probability for GC.
+    JS_updateMallocCounter(cx, 2 * sizeof(XPCWrappedNative));
+
+    return true;
+}
+
+
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(XPCWrappedNative)
+  NS_INTERFACE_MAP_ENTRY(nsIXPConnectWrappedNative)
+  NS_INTERFACE_MAP_ENTRY(nsIXPConnectJSObjectHolder)
+  NS_INTERFACE_MAP_ENTRY_AMBIGUOUS(nsISupports, nsIXPConnectWrappedNative)
+NS_INTERFACE_MAP_END
+
+NS_IMPL_CYCLE_COLLECTING_ADDREF(XPCWrappedNative)
+
+// Release calls Destroy() immediately when the refcount drops to 0 to
+// clear the weak references nsXPConnect has to XPCWNs and to ensure there
+// are no pointers to dying protos.
+NS_IMPL_CYCLE_COLLECTING_RELEASE_WITH_LAST_RELEASE(XPCWrappedNative, Destroy())
+
+/*
+ *  Wrapped Native lifetime management is messy!
+ *
+ *  - At creation we push the refcount to 2 (only one of which is owned by
+ *    the native caller that caused the wrapper creation).
+ *  - During the JS GC Mark phase we mark any wrapper with a refcount > 1.
+ *  - The *only* thing that can make the wrapper get destroyed is the
+ *    finalization of mFlatJSObject. And *that* should only happen if the only
+ *    reference is the single extra (internal) reference we hold.
+ *
+ *  - The wrapper has a pointer to the nsISupports 'view' of the wrapped native
+ *    object i.e... mIdentity. This is held until the wrapper's refcount goes
+ *    to zero and the wrapper is released, or until an expired wrapper (i.e.,
+ *    one unlinked by the cycle collector) has had its JS object finalized.
+ *
+ *  - The wrapper also has 'tearoffs'. It has one tearoff for each interface
+ *    that is actually used on the native object. 'Used' means we have either
+ *    needed to QueryInterface to verify the availability of that interface
+ *    of that we've had to QueryInterface in order to actually make a call
+ *    into the wrapped object via the pointer for the given interface.
+ *
+ *  - Each tearoff's 'mNative' member (if non-null) indicates one reference
+ *    held by our wrapper on the wrapped native for the given interface
+ *    associated with the tearoff. If we release that reference then we set
+ *    the tearoff's 'mNative' to null.
+ *
+ *  - We use the occasion of the JavaScript GCCallback for the JSGC_MARK_END
+ *    event to scan the tearoffs of all wrappers for non-null mNative members
+ *    that represent unused references. We can tell that a given tearoff's
+ *    mNative is unused by noting that no live XPCCallContexts hold a pointer
+ *    to the tearoff.
+ *
+ *  - As a time/space tradeoff we may decide to not do this scanning on
+ *    *every* JavaScript GC. We *do* want to do this *sometimes* because
+ *    we want to allow for wrapped native's to do their own tearoff patterns.
+ *    So, we want to avoid holding references to interfaces that we don't need.
+ *    At the same time, we don't want to be bracketing every call into a
+ *    wrapped native object with a QueryInterface/Release pair. And we *never*
+ *    make a call into the object except via the correct interface for which
+ *    we've QI'd.
+ *
+ *  - Each tearoff *can* have a mJSObject whose lazily resolved properties
+ *    represent the methods/attributes/constants of that specific interface.
+ *    This is optionally reflected into JavaScript as "foo.nsIFoo" when "foo"
+ *    is the name of mFlatJSObject and "nsIFoo" is the name of the given
+ *    interface associated with the tearoff. When we create the tearoff's
+ *    mJSObject we set it's parent to be mFlatJSObject. This way we know that
+ *    when mFlatJSObject get's collected there are no outstanding reachable
+ *    tearoff mJSObjects. Note that we must clear the private of any lingering
+ *    mJSObjects at this point because we have no guarentee of the *order* of
+ *    finalization within a given gc cycle.
+ */
+
+void
+XPCWrappedNative::FlatJSObjectFinalized()
+{
+    if (!IsValid())
+        return;
+
+    // Iterate the tearoffs and null out each of their JSObject's privates.
+    // This will keep them from trying to access their pointers to the
+    // dying tearoff object. We can safely assume that those remaining
+    // JSObjects are about to be finalized too.
+
+    for (XPCWrappedNativeTearOff* to = &mFirstTearOff; to; to = to->GetNextTearOff()) {
+        JSObject* jso = to->GetJSObjectPreserveColor();
+        if (jso) {
+            JS_SetPrivate(jso, nullptr);
+#ifdef DEBUG
+            JS_UpdateWeakPointerAfterGCUnbarriered(&jso);
+            MOZ_ASSERT(!jso);
+#endif
+            to->JSObjectFinalized();
+        }
+
+        // We also need to release any native pointers held...
+        RefPtr<nsISupports> native = to->TakeNative();
+        if (native && GetContext()) {
+            DeferredFinalize(native.forget().take());
+        }
+
+        to->SetInterface(nullptr);
+    }
+
+    nsWrapperCache* cache = nullptr;
+    CallQueryInterface(mIdentity, &cache);
+    if (cache)
+        cache->ClearWrapper();
+
+    mFlatJSObject = nullptr;
+    mFlatJSObject.unsetFlags(FLAT_JS_OBJECT_VALID);
+
+    MOZ_ASSERT(mIdentity, "bad pointer!");
+#ifdef XP_WIN
+    // Try to detect free'd pointer
+    MOZ_ASSERT(*(int*)mIdentity.get() != 0xdddddddd, "bad pointer!");
+    MOZ_ASSERT(*(int*)mIdentity.get() != 0,          "bad pointer!");
+#endif
+
+    if (IsWrapperExpired()) {
+        Destroy();
+    }
+
+    // Note that it's not safe to touch mNativeWrapper here since it's
+    // likely that it has already been finalized.
+
+    Release();
+}
+
+void
+XPCWrappedNative::FlatJSObjectMoved(JSObject* obj, const JSObject* old)
+{
+    JS::AutoAssertGCCallback inCallback(obj);
+    MOZ_ASSERT(mFlatJSObject.unbarrieredGetPtr() == old);
+
+    nsWrapperCache* cache = nullptr;
+    CallQueryInterface(mIdentity, &cache);
+    if (cache)
+        cache->UpdateWrapper(obj, old);
+
+    mFlatJSObject = obj;
+}
+
+void
+XPCWrappedNative::SystemIsBeingShutDown()
+{
+    if (!IsValid())
+        return;
+
+    // The long standing strategy is to leak some objects still held at shutdown.
+    // The general problem is that propagating release out of xpconnect at
+    // shutdown time causes a world of problems.
+
+    // We leak mIdentity (see above).
+
+    // Short circuit future finalization.
+    JS_SetPrivate(mFlatJSObject, nullptr);
+    mFlatJSObject = nullptr;
+    mFlatJSObject.unsetFlags(FLAT_JS_OBJECT_VALID);
+
+    XPCWrappedNativeProto* proto = GetProto();
+
+    if (HasProto())
+        proto->SystemIsBeingShutDown();
+
+    // We don't destroy mScriptableInfo here. The destructor will do it.
+
+    // Cleanup the tearoffs.
+    for (XPCWrappedNativeTearOff* to = &mFirstTearOff; to; to = to->GetNextTearOff()) {
+        if (JSObject* jso = to->GetJSObjectPreserveColor()) {
+            JS_SetPrivate(jso, nullptr);
+            to->SetJSObject(nullptr);
+        }
+        // We leak the tearoff mNative
+        // (for the same reason we leak mIdentity - see above).
+        Unused << to->TakeNative().take();
+        to->SetInterface(nullptr);
+    }
+}
+
+/***************************************************************************/
+
+// Dynamically ensure that two objects don't end up with the same private.
+class MOZ_STACK_CLASS AutoClonePrivateGuard {
+public:
+    AutoClonePrivateGuard(JSContext* cx, JSObject* aOld, JSObject* aNew)
+        : mOldReflector(cx, aOld), mNewReflector(cx, aNew)
+    {
+        MOZ_ASSERT(JS_GetPrivate(aOld) == JS_GetPrivate(aNew));
+    }
+
+    ~AutoClonePrivateGuard()
+    {
+        if (JS_GetPrivate(mOldReflector)) {
+            JS_SetPrivate(mNewReflector, nullptr);
+        }
+    }
+
+private:
+    RootedObject mOldReflector;
+    RootedObject mNewReflector;
+};
+
+bool
+XPCWrappedNative::ExtendSet(XPCNativeInterface* aInterface)
+{
+    if (!mSet->HasInterface(aInterface)) {
+        XPCNativeSetKey key(mSet, aInterface);
+        RefPtr<XPCNativeSet> newSet =
+            XPCNativeSet::GetNewOrUsed(&key);
+        if (!newSet)
+            return false;
+
+        mSet = newSet.forget();
+    }
+    return true;
+}
+
+XPCWrappedNativeTearOff*
+XPCWrappedNative::FindTearOff(XPCNativeInterface* aInterface,
+                              bool needJSObject /* = false */,
+                              nsresult* pError /* = nullptr */)
+{
+    AutoJSContext cx;
+    nsresult rv = NS_OK;
+    XPCWrappedNativeTearOff* to;
+    XPCWrappedNativeTearOff* firstAvailable = nullptr;
+
+    XPCWrappedNativeTearOff* lastTearOff;
+    for (lastTearOff = to = &mFirstTearOff;
+         to;
+         lastTearOff = to, to = to->GetNextTearOff()) {
+        if (to->GetInterface() == aInterface) {
+            if (needJSObject && !to->GetJSObjectPreserveColor()) {
+                AutoMarkingWrappedNativeTearOffPtr tearoff(cx, to);
+                bool ok = InitTearOffJSObject(to);
+                // During shutdown, we don't sweep tearoffs.  So make sure
+                // to unmark manually in case the auto-marker marked us.
+                // We shouldn't ever be getting here _during_ our
+                // Mark/Sweep cycle, so this should be safe.
+                to->Unmark();
+                if (!ok) {
+                    to = nullptr;
+                    rv = NS_ERROR_OUT_OF_MEMORY;
+                }
+            }
+            if (pError)
+                *pError = rv;
+            return to;
+        }
+        if (!firstAvailable && to->IsAvailable())
+            firstAvailable = to;
+    }
+
+    to = firstAvailable;
+
+    if (!to) {
+        to = lastTearOff->AddTearOff();
+    }
+
+    {
+        // Scope keeps |tearoff| from leaking across the rest of the function.
+        AutoMarkingWrappedNativeTearOffPtr tearoff(cx, to);
+        rv = InitTearOff(to, aInterface, needJSObject);
+        // During shutdown, we don't sweep tearoffs.  So make sure to unmark
+        // manually in case the auto-marker marked us.  We shouldn't ever be
+        // getting here _during_ our Mark/Sweep cycle, so this should be safe.
+        to->Unmark();
+        if (NS_FAILED(rv))
+            to = nullptr;
+    }
+
+    if (pError)
+        *pError = rv;
+    return to;
+}
+
+XPCWrappedNativeTearOff*
+XPCWrappedNative::FindTearOff(const nsIID& iid) {
+    RefPtr<XPCNativeInterface> iface = XPCNativeInterface::GetNewOrUsed(&iid);
+    return iface ? FindTearOff(iface) : nullptr;
+}
+
+nsresult
+XPCWrappedNative::InitTearOff(XPCWrappedNativeTearOff* aTearOff,
+                              XPCNativeInterface* aInterface,
+                              bool needJSObject)
+{
+    AutoJSContext cx;
+
+    // Determine if the object really does this interface...
+
+    const nsIID* iid = aInterface->GetIID();
+    nsISupports* identity = GetIdentityObject();
+
+    // This is an nsRefPtr instead of an nsCOMPtr because it may not be the
+    // canonical nsISupports for this object.
+    RefPtr<nsISupports> qiResult;
+
+    // If the scriptable helper forbids us from reflecting additional
+    // interfaces, then don't even try the QI, just fail.
+    if (mScriptableInfo &&
+        mScriptableInfo->GetFlags().ClassInfoInterfacesOnly() &&
+        !mSet->HasInterface(aInterface) &&
+        !mSet->HasInterfaceWithAncestor(aInterface)) {
+        return NS_ERROR_NO_INTERFACE;
+    }
+
+    // We are about to call out to other code.
+    // So protect our intended tearoff.
+
+    aTearOff->SetReserved();
+
+    if (NS_FAILED(identity->QueryInterface(*iid, getter_AddRefs(qiResult))) || !qiResult) {
+        aTearOff->SetInterface(nullptr);
+        return NS_ERROR_NO_INTERFACE;
+    }
+
+    // Guard against trying to build a tearoff for a shared nsIClassInfo.
+    if (iid->Equals(NS_GET_IID(nsIClassInfo))) {
+        nsCOMPtr<nsISupports> alternate_identity(do_QueryInterface(qiResult));
+        if (alternate_identity.get() != identity) {
+            aTearOff->SetInterface(nullptr);
+            return NS_ERROR_NO_INTERFACE;
+        }
+    }
+
+    // Guard against trying to build a tearoff for an interface that is
+    // aggregated and is implemented as a nsIXPConnectWrappedJS using this
+    // self-same JSObject. The XBL system does this. If we mutate the set
+    // of this wrapper then we will shadow the method that XBL has added to
+    // the JSObject that it has inserted in the JS proto chain between our
+    // JSObject and our XPCWrappedNativeProto's JSObject. If we let this
+    // set mutation happen then the interface's methods will be added to
+    // our JSObject, but calls on those methods will get routed up to
+    // native code and into the wrappedJS - which will do a method lookup
+    // on *our* JSObject and find the same method and make another call
+    // into an infinite loop.
+    // see: http://bugzilla.mozilla.org/show_bug.cgi?id=96725
+
+    // The code in this block also does a check for the double wrapped
+    // nsIPropertyBag case.
+
+    nsCOMPtr<nsIXPConnectWrappedJS> wrappedJS(do_QueryInterface(qiResult));
+    if (wrappedJS) {
+        RootedObject jso(cx, wrappedJS->GetJSObject());
+        if (jso == mFlatJSObject) {
+            // The implementing JSObject is the same as ours! Just say OK
+            // without actually extending the set.
+            //
+            // XXX It is a little cheesy to have FindTearOff return an
+            // 'empty' tearoff. But this is the centralized place to do the
+            // QI activities on the underlying object. *And* most caller to
+            // FindTearOff only look for a non-null result and ignore the
+            // actual tearoff returned. The only callers that do use the
+            // returned tearoff make sure to check for either a non-null
+            // JSObject or a matching Interface before proceeding.
+            // I think we can get away with this bit of ugliness.
+
+            aTearOff->SetInterface(nullptr);
+            return NS_OK;
+        }
+
+        // Decide whether or not to expose nsIPropertyBag to calling
+        // JS code in the double wrapped case.
+        //
+        // Our rule here is that when JSObjects are double wrapped and
+        // exposed to other JSObjects then the nsIPropertyBag interface
+        // is only exposed on an 'opt-in' basis; i.e. if the underlying
+        // JSObject wants other JSObjects to be able to see this interface
+        // then it must implement QueryInterface and not throw an exception
+        // when asked for nsIPropertyBag. It need not actually *implement*
+        // nsIPropertyBag - xpconnect will do that work.
+
+        if (iid->Equals(NS_GET_IID(nsIPropertyBag)) && jso) {
+            RefPtr<nsXPCWrappedJSClass> clasp = nsXPCWrappedJSClass::GetNewOrUsed(cx, *iid);
+            if (clasp) {
+                RootedObject answer(cx, clasp->CallQueryInterfaceOnJSObject(cx, jso, *iid));
+
+                if (!answer) {
+                    aTearOff->SetInterface(nullptr);
+                    return NS_ERROR_NO_INTERFACE;
+                }
+            }
+        }
+    }
+
+    if (NS_FAILED(nsXPConnect::SecurityManager()->CanCreateWrapper(cx, *iid, identity,
+                                                                   GetClassInfo()))) {
+        // the security manager vetoed. It should have set an exception.
+        aTearOff->SetInterface(nullptr);
+        return NS_ERROR_XPC_SECURITY_MANAGER_VETO;
+    }
+
+    // If this is not already in our set we need to extend our set.
+    // Note: we do not cache the result of the previous call to HasInterface()
+    // because we unlocked and called out in the interim and the result of the
+    // previous call might not be correct anymore.
+
+    if (!mSet->HasInterface(aInterface) && !ExtendSet(aInterface)) {
+        aTearOff->SetInterface(nullptr);
+        return NS_ERROR_NO_INTERFACE;
+    }
+
+    aTearOff->SetInterface(aInterface);
+    aTearOff->SetNative(qiResult);
+    if (needJSObject && !InitTearOffJSObject(aTearOff))
+        return NS_ERROR_OUT_OF_MEMORY;
+
+    return NS_OK;
+}
+
+bool
+XPCWrappedNative::InitTearOffJSObject(XPCWrappedNativeTearOff* to)
+{
+    AutoJSContext cx;
+
+    JSObject* obj = JS_NewObject(cx, Jsvalify(&XPC_WN_Tearoff_JSClass));
+    if (!obj)
+        return false;
+
+    JS_SetPrivate(obj, to);
+    to->SetJSObject(obj);
+
+    js::SetReservedSlot(obj, XPC_WN_TEAROFF_FLAT_OBJECT_SLOT,
+                        JS::ObjectValue(*mFlatJSObject));
+    return true;
+}
+
+/***************************************************************************/
+
+static bool Throw(nsresult errNum, XPCCallContext& ccx)
+{
+    XPCThrower::Throw(errNum, ccx);
+    return false;
+}
+
+/***************************************************************************/
+
+class MOZ_STACK_CLASS CallMethodHelper
+{
+    XPCCallContext& mCallContext;
+    nsresult mInvokeResult;
+    nsIInterfaceInfo* const mIFaceInfo;
+    const nsXPTMethodInfo* mMethodInfo;
+    nsISupports* const mCallee;
+    const uint16_t mVTableIndex;
+    HandleId mIdxValueId;
+
+    AutoTArray<nsXPTCVariant, 8> mDispatchParams;
+    uint8_t mJSContextIndex; // TODO make const
+    uint8_t mOptArgcIndex; // TODO make const
+
+    Value* const mArgv;
+    const uint32_t mArgc;
+
+    MOZ_ALWAYS_INLINE bool
+    GetArraySizeFromParam(uint8_t paramIndex, HandleValue maybeArray, uint32_t* result);
+
+    MOZ_ALWAYS_INLINE bool
+    GetInterfaceTypeFromParam(uint8_t paramIndex,
+                              const nsXPTType& datum_type,
+                              nsID* result) const;
+
+    MOZ_ALWAYS_INLINE bool
+    GetOutParamSource(uint8_t paramIndex, MutableHandleValue srcp) const;
+
+    MOZ_ALWAYS_INLINE bool
+    GatherAndConvertResults();
+
+    MOZ_ALWAYS_INLINE bool
+    QueryInterfaceFastPath();
+
+    nsXPTCVariant*
+    GetDispatchParam(uint8_t paramIndex)
+    {
+        if (paramIndex >= mJSContextIndex)
+            paramIndex += 1;
+        if (paramIndex >= mOptArgcIndex)
+            paramIndex += 1;
+        return &mDispatchParams[paramIndex];
+    }
+    const nsXPTCVariant*
+    GetDispatchParam(uint8_t paramIndex) const
+    {
+        return const_cast<CallMethodHelper*>(this)->GetDispatchParam(paramIndex);
+    }
+
+    MOZ_ALWAYS_INLINE bool InitializeDispatchParams();
+
+    MOZ_ALWAYS_INLINE bool ConvertIndependentParams(bool* foundDependentParam);
+    MOZ_ALWAYS_INLINE bool ConvertIndependentParam(uint8_t i);
+    MOZ_ALWAYS_INLINE bool ConvertDependentParams();
+    MOZ_ALWAYS_INLINE bool ConvertDependentParam(uint8_t i);
+
+    MOZ_ALWAYS_INLINE void CleanupParam(nsXPTCMiniVariant& param, nsXPTType& type);
+
+    MOZ_ALWAYS_INLINE bool AllocateStringClass(nsXPTCVariant* dp,
+                                               const nsXPTParamInfo& paramInfo);
+
+    MOZ_ALWAYS_INLINE nsresult Invoke();
+
+public:
+
+    explicit CallMethodHelper(XPCCallContext& ccx)
+        : mCallContext(ccx)
+        , mInvokeResult(NS_ERROR_UNEXPECTED)
+        , mIFaceInfo(ccx.GetInterface()->GetInterfaceInfo())
+        , mMethodInfo(nullptr)
+        , mCallee(ccx.GetTearOff()->GetNative())
+        , mVTableIndex(ccx.GetMethodIndex())
+        , mIdxValueId(ccx.GetContext()->GetStringID(XPCJSContext::IDX_VALUE))
+        , mJSContextIndex(UINT8_MAX)
+        , mOptArgcIndex(UINT8_MAX)
+        , mArgv(ccx.GetArgv())
+        , mArgc(ccx.GetArgc())
+
+    {
+        // Success checked later.
+        mIFaceInfo->GetMethodInfo(mVTableIndex, &mMethodInfo);
+    }
+
+    ~CallMethodHelper();
+
+    MOZ_ALWAYS_INLINE bool Call();
+
+};
+
+// static
+bool
+XPCWrappedNative::CallMethod(XPCCallContext& ccx,
+                             CallMode mode /*= CALL_METHOD */)
+{
+    nsresult rv = ccx.CanCallNow();
+    if (NS_FAILED(rv)) {
+        return Throw(rv, ccx);
+    }
+
+    return CallMethodHelper(ccx).Call();
+}
+
+bool
+CallMethodHelper::Call()
+{
+    mCallContext.SetRetVal(JS::UndefinedValue());
+
+    XPCJSContext::Get()->SetPendingException(nullptr);
+
+    if (mVTableIndex == 0) {
+        return QueryInterfaceFastPath();
+    }
+
+    if (!mMethodInfo) {
+        Throw(NS_ERROR_XPC_CANT_GET_METHOD_INFO, mCallContext);
+        return false;
+    }
+
+    if (!InitializeDispatchParams())
+        return false;
+
+    // Iterate through the params doing conversions of independent params only.
+    // When we later convert the dependent params (if any) we will know that
+    // the params upon which they depend will have already been converted -
+    // regardless of ordering.
+    bool foundDependentParam = false;
+    if (!ConvertIndependentParams(&foundDependentParam))
+        return false;
+
+    if (foundDependentParam && !ConvertDependentParams())
+        return false;
+
+    mInvokeResult = Invoke();
+
+    if (JS_IsExceptionPending(mCallContext)) {
+        return false;
+    }
+
+    if (NS_FAILED(mInvokeResult)) {
+        ThrowBadResult(mInvokeResult, mCallContext);
+        return false;
+    }
+
+    return GatherAndConvertResults();
+}
+
+CallMethodHelper::~CallMethodHelper()
+{
+    uint8_t paramCount = mMethodInfo->GetParamCount();
+    if (mDispatchParams.Length()) {
+        for (uint8_t i = 0; i < paramCount; i++) {
+            nsXPTCVariant* dp = GetDispatchParam(i);
+            const nsXPTParamInfo& paramInfo = mMethodInfo->GetParam(i);
+
+            if (paramInfo.GetType().IsArray()) {
+                void* p = dp->val.p;
+                if (!p)
+                    continue;
+
+                // Clean up the array contents if necessary.
+                if (dp->DoesValNeedCleanup()) {
+                    // We need some basic information to properly destroy the array.
+                    uint32_t array_count = 0;
+                    nsXPTType datum_type;
+                    if (!GetArraySizeFromParam(i, UndefinedHandleValue, &array_count) ||
+                        !NS_SUCCEEDED(mIFaceInfo->GetTypeForParam(mVTableIndex,
+                                                                  &paramInfo,
+                                                                  1, &datum_type))) {
+                        // XXXbholley - I'm not convinced that the above calls will
+                        // ever fail.
+                        NS_ERROR("failed to get array information, we'll leak here");
+                        continue;
+                    }
+
+                    // Loop over the array contents. For each one, we create a
+                    // dummy 'val' and pass it to the cleanup helper.
+                    for (uint32_t k = 0; k < array_count; k++) {
+                        nsXPTCMiniVariant v;
+                        v.val.p = static_cast<void**>(p)[k];
+                        CleanupParam(v, datum_type);
+                    }
+                }
+
+                // always free the array itself
+                free(p);
+            } else {
+                // Clean up single parameters (if requested).
+                if (dp->DoesValNeedCleanup())
+                    CleanupParam(*dp, dp->type);
+            }
+        }
+    }
+}
+
+bool
+CallMethodHelper::GetArraySizeFromParam(uint8_t paramIndex,
+                                        HandleValue maybeArray,
+                                        uint32_t* result)
+{
+    nsresult rv;
+    const nsXPTParamInfo& paramInfo = mMethodInfo->GetParam(paramIndex);
+
+    // TODO fixup the various exceptions that are thrown
+
+    rv = mIFaceInfo->GetSizeIsArgNumberForParam(mVTableIndex, &paramInfo, 0, &paramIndex);
+    if (NS_FAILED(rv))
+        return Throw(NS_ERROR_XPC_CANT_GET_ARRAY_INFO, mCallContext);
+
+    // If the array length wasn't passed, it might have been listed as optional.
+    // When converting arguments from JS to C++, we pass the array as |maybeArray|,
+    // and give ourselves the chance to infer the length. Once we have it, we stick
+    // it in the right slot so that we can find it again when cleaning up the params.
+    // from the array.
+    if (paramIndex >= mArgc && maybeArray.isObject()) {
+        MOZ_ASSERT(mMethodInfo->GetParam(paramIndex).IsOptional());
+        RootedObject arrayOrNull(mCallContext, maybeArray.isObject() ? &maybeArray.toObject()
+                                                                     : nullptr);
+
+        bool isArray;
+        if (!JS_IsArrayObject(mCallContext, maybeArray, &isArray) ||
+            !isArray ||
+            !JS_GetArrayLength(mCallContext, arrayOrNull, &GetDispatchParam(paramIndex)->val.u32))
+        {
+            return Throw(NS_ERROR_XPC_CANT_CONVERT_OBJECT_TO_ARRAY, mCallContext);
+        }
+    }
+
+    *result = GetDispatchParam(paramIndex)->val.u32;
+
+    return true;
+}
+
+bool
+CallMethodHelper::GetInterfaceTypeFromParam(uint8_t paramIndex,
+                                            const nsXPTType& datum_type,
+                                            nsID* result) const
+{
+    nsresult rv;
+    const nsXPTParamInfo& paramInfo = mMethodInfo->GetParam(paramIndex);
+    uint8_t tag = datum_type.TagPart();
+
+    // TODO fixup the various exceptions that are thrown
+
+    if (tag == nsXPTType::T_INTERFACE) {
+        rv = mIFaceInfo->GetIIDForParamNoAlloc(mVTableIndex, &paramInfo, result);
+        if (NS_FAILED(rv))
+            return ThrowBadParam(NS_ERROR_XPC_CANT_GET_PARAM_IFACE_INFO,
+                                 paramIndex, mCallContext);
+    } else if (tag == nsXPTType::T_INTERFACE_IS) {
+        rv = mIFaceInfo->GetInterfaceIsArgNumberForParam(mVTableIndex, &paramInfo,
+                                                         &paramIndex);
+        if (NS_FAILED(rv))
+            return Throw(NS_ERROR_XPC_CANT_GET_ARRAY_INFO, mCallContext);
+
+        nsID* p = (nsID*) GetDispatchParam(paramIndex)->val.p;
+        if (!p)
+            return ThrowBadParam(NS_ERROR_XPC_CANT_GET_PARAM_IFACE_INFO,
+                                 paramIndex, mCallContext);
+        *result = *p;
+    }
+    return true;
+}
+
+bool
+CallMethodHelper::GetOutParamSource(uint8_t paramIndex, MutableHandleValue srcp) const
+{
+    const nsXPTParamInfo& paramInfo = mMethodInfo->GetParam(paramIndex);
+
+    MOZ_ASSERT(!paramInfo.IsDipper(), "Dipper params are handled separately");
+    if (paramInfo.IsOut() && !paramInfo.IsRetval()) {
+        MOZ_ASSERT(paramIndex < mArgc || paramInfo.IsOptional(),
+                   "Expected either enough arguments or an optional argument");
+        Value arg = paramIndex < mArgc ? mArgv[paramIndex] : JS::NullValue();
+        if (paramIndex < mArgc) {
+            RootedObject obj(mCallContext);
+            if (!arg.isPrimitive())
+                obj = &arg.toObject();
+            if (!obj || !JS_GetPropertyById(mCallContext, obj, mIdxValueId, srcp)) {
+                // Explicitly passed in unusable value for out param.  Note
+                // that if i >= mArgc we already know that |arg| is JS::NullValue(),
+                // and that's ok.
+                ThrowBadParam(NS_ERROR_XPC_NEED_OUT_OBJECT, paramIndex,
+                              mCallContext);
+                return false;
+            }
+        }
+    }
+
+    return true;
+}
+
+bool
+CallMethodHelper::GatherAndConvertResults()
+{
+    // now we iterate through the native params to gather and convert results
+    uint8_t paramCount = mMethodInfo->GetParamCount();
+    for (uint8_t i = 0; i < paramCount; i++) {
+        const nsXPTParamInfo& paramInfo = mMethodInfo->GetParam(i);
+        if (!paramInfo.IsOut() && !paramInfo.IsDipper())
+            continue;
+
+        const nsXPTType& type = paramInfo.GetType();
+        nsXPTCVariant* dp = GetDispatchParam(i);
+        RootedValue v(mCallContext, NullValue());
+        uint32_t array_count = 0;
+        nsXPTType datum_type;
+        bool isArray = type.IsArray();
+        bool isSizedString = isArray ?
+                false :
+                type.TagPart() == nsXPTType::T_PSTRING_SIZE_IS ||
+                type.TagPart() == nsXPTType::T_PWSTRING_SIZE_IS;
+
+        if (isArray) {
+            if (NS_FAILED(mIFaceInfo->GetTypeForParam(mVTableIndex, &paramInfo, 1,
+                                                      &datum_type))) {
+                Throw(NS_ERROR_XPC_CANT_GET_ARRAY_INFO, mCallContext);
+                return false;
+            }
+        } else
+            datum_type = type;
+
+        if (isArray || isSizedString) {
+            if (!GetArraySizeFromParam(i, UndefinedHandleValue, &array_count))
+                return false;
+        }
+
+        nsID param_iid;
+        if (datum_type.IsInterfacePointer() &&
+            !GetInterfaceTypeFromParam(i, datum_type, &param_iid))
+            return false;
+
+        nsresult err;
+        if (isArray) {
+            if (!XPCConvert::NativeArray2JS(&v, (const void**)&dp->val,
+                                            datum_type, &param_iid,
+                                            array_count, &err)) {
+                // XXX need exception scheme for arrays to indicate bad element
+                ThrowBadParam(err, i, mCallContext);
+                return false;
+            }
+        } else if (isSizedString) {
+            if (!XPCConvert::NativeStringWithSize2JS(&v,
+                                                     (const void*)&dp->val,
+                                                     datum_type,
+                                                     array_count, &err)) {
+                ThrowBadParam(err, i, mCallContext);
+                return false;
+            }
+        } else {
+            if (!XPCConvert::NativeData2JS(&v, &dp->val, datum_type,
+                                           &param_iid, &err)) {
+                ThrowBadParam(err, i, mCallContext);
+                return false;
+            }
+        }
+
+        if (paramInfo.IsRetval()) {
+            mCallContext.SetRetVal(v);
+        } else if (i < mArgc) {
+            // we actually assured this before doing the invoke
+            MOZ_ASSERT(mArgv[i].isObject(), "out var is not object");
+            RootedObject obj(mCallContext, &mArgv[i].toObject());
+            if (!JS_SetPropertyById(mCallContext, obj, mIdxValueId, v)) {
+                ThrowBadParam(NS_ERROR_XPC_CANT_SET_OUT_VAL, i, mCallContext);
+                return false;
+            }
+        } else {
+            MOZ_ASSERT(paramInfo.IsOptional(),
+                       "Expected either enough arguments or an optional argument");
+        }
+    }
+
+    return true;
+}
+
+bool
+CallMethodHelper::QueryInterfaceFastPath()
+{
+    MOZ_ASSERT(mVTableIndex == 0,
+               "Using the QI fast-path for a method other than QueryInterface");
+
+    if (mArgc < 1) {
+        Throw(NS_ERROR_XPC_NOT_ENOUGH_ARGS, mCallContext);
+        return false;
+    }
+
+    if (!mArgv[0].isObject()) {
+        ThrowBadParam(NS_ERROR_XPC_BAD_CONVERT_JS, 0, mCallContext);
+        return false;
+    }
+
+    const nsID* iid = xpc_JSObjectToID(mCallContext, &mArgv[0].toObject());
+    if (!iid) {
+        ThrowBadParam(NS_ERROR_XPC_BAD_CONVERT_JS, 0, mCallContext);
+        return false;
+    }
+
+    nsISupports* qiresult = nullptr;
+    mInvokeResult = mCallee->QueryInterface(*iid, (void**) &qiresult);
+
+    if (NS_FAILED(mInvokeResult)) {
+        ThrowBadResult(mInvokeResult, mCallContext);
+        return false;
+    }
+
+    RootedValue v(mCallContext, NullValue());
+    nsresult err;
+    bool success =
+        XPCConvert::NativeData2JS(&v, &qiresult,
+                                  nsXPTType::T_INTERFACE_IS,
+                                  iid, &err);
+    NS_IF_RELEASE(qiresult);
+
+    if (!success) {
+        ThrowBadParam(err, 0, mCallContext);
+        return false;
+    }
+
+    mCallContext.SetRetVal(v);
+    return true;
+}
+
+bool
+CallMethodHelper::InitializeDispatchParams()
+{
+    const uint8_t wantsOptArgc = mMethodInfo->WantsOptArgc() ? 1 : 0;
+    const uint8_t wantsJSContext = mMethodInfo->WantsContext() ? 1 : 0;
+    const uint8_t paramCount = mMethodInfo->GetParamCount();
+    uint8_t requiredArgs = paramCount;
+    uint8_t hasRetval = 0;
+
+    // XXX ASSUMES that retval is last arg. The xpidl compiler ensures this.
+    if (paramCount && mMethodInfo->GetParam(paramCount-1).IsRetval()) {
+        hasRetval = 1;
+        requiredArgs--;
+    }
+
+    if (mArgc < requiredArgs || wantsOptArgc) {
+        if (wantsOptArgc)
+            mOptArgcIndex = requiredArgs;
+
+        // skip over any optional arguments
+        while (requiredArgs && mMethodInfo->GetParam(requiredArgs-1).IsOptional())
+            requiredArgs--;
+
+        if (mArgc < requiredArgs) {
+            Throw(NS_ERROR_XPC_NOT_ENOUGH_ARGS, mCallContext);
+            return false;
+        }
+    }
+
+    if (wantsJSContext) {
+        if (wantsOptArgc)
+            // Need to bump mOptArgcIndex up one here.
+            mJSContextIndex = mOptArgcIndex++;
+        else if (mMethodInfo->IsSetter() || mMethodInfo->IsGetter())
+            // For attributes, we always put the JSContext* first.
+            mJSContextIndex = 0;
+        else
+            mJSContextIndex = paramCount - hasRetval;
+    }
+
+    // iterate through the params to clear flags (for safe cleanup later)
+    for (uint8_t i = 0; i < paramCount + wantsJSContext + wantsOptArgc; i++) {
+        nsXPTCVariant* dp = mDispatchParams.AppendElement();
+        dp->ClearFlags();
+        dp->val.p = nullptr;
+    }
+
+    // Fill in the JSContext argument
+    if (wantsJSContext) {
+        nsXPTCVariant* dp = &mDispatchParams[mJSContextIndex];
+        dp->type = nsXPTType::T_VOID;
+        dp->val.p = mCallContext;
+    }
+
+    // Fill in the optional_argc argument
+    if (wantsOptArgc) {
+        nsXPTCVariant* dp = &mDispatchParams[mOptArgcIndex];
+        dp->type = nsXPTType::T_U8;
+        dp->val.u8 = std::min<uint32_t>(mArgc, paramCount) - requiredArgs;
+    }
+
+    return true;
+}
+
+bool
+CallMethodHelper::ConvertIndependentParams(bool* foundDependentParam)
+{
+    const uint8_t paramCount = mMethodInfo->GetParamCount();
+    for (uint8_t i = 0; i < paramCount; i++) {
+        const nsXPTParamInfo& paramInfo = mMethodInfo->GetParam(i);
+
+        if (paramInfo.GetType().IsDependent())
+            *foundDependentParam = true;
+        else if (!ConvertIndependentParam(i))
+            return false;
+
+    }
+
+    return true;
+}
+
+bool
+CallMethodHelper::ConvertIndependentParam(uint8_t i)
+{
+    const nsXPTParamInfo& paramInfo = mMethodInfo->GetParam(i);
+    const nsXPTType& type = paramInfo.GetType();
+    uint8_t type_tag = type.TagPart();
+    nsXPTCVariant* dp = GetDispatchParam(i);
+    dp->type = type;
+    MOZ_ASSERT(!paramInfo.IsShared(), "[shared] implies [noscript]!");
+
+    // String classes are always "in" - those that are marked "out" are converted
+    // by the XPIDL compiler to "in+dipper". See the note above IsDipper() in
+    // xptinfo.h.
+    //
+    // Also note that the fact that we bail out early for dipper parameters means
+    // that "inout" dipper parameters don't work - see bug 687612.
+    if (paramInfo.IsStringClass()) {
+        if (!AllocateStringClass(dp, paramInfo))
+            return false;
+        if (paramInfo.IsDipper()) {
+            // We've allocated our string class explicitly, so we don't need
+            // to do any conversions on the incoming argument. However, we still
+            // need to verify that it's an object, so that we don't get surprised
+            // later on when trying to assign the result to .value.
+            if (i < mArgc && !mArgv[i].isObject()) {
+                ThrowBadParam(NS_ERROR_XPC_NEED_OUT_OBJECT, i, mCallContext);
+                return false;
+            }
+            return true;
+        }
+    }
+
+    // Specify the correct storage/calling semantics.
+    if (paramInfo.IsIndirect())
+        dp->SetIndirect();
+
+    // The JSVal proper is always stored within the 'val' union and passed
+    // indirectly, regardless of in/out-ness.
+    if (type_tag == nsXPTType::T_JSVAL) {
+        // Root the value.
+        dp->val.j.setUndefined();
+        if (!js::AddRawValueRoot(mCallContext, &dp->val.j, "XPCWrappedNative::CallMethod param"))
+            return false;
+    }
+
+    // Flag cleanup for anything that isn't self-contained.
+    if (!type.IsArithmetic())
+        dp->SetValNeedsCleanup();
+
+    // Even if there's nothing to convert, we still need to examine the
+    // JSObject container for out-params. If it's null or otherwise invalid,
+    // we want to know before the call, rather than after.
+    //
+    // This is a no-op for 'in' params.
+    RootedValue src(mCallContext);
+    if (!GetOutParamSource(i, &src))
+        return false;
+
+    // All that's left to do is value conversion. Bail early if we don't need
+    // to do that.
+    if (!paramInfo.IsIn())
+        return true;
+
+    // We're definitely some variety of 'in' now, so there's something to
+    // convert. The source value for conversion depends on whether we're
+    // dealing with an 'in' or an 'inout' parameter. 'inout' was handled above,
+    // so all that's left is 'in'.
+    if (!paramInfo.IsOut()) {
+        // Handle the 'in' case.
+        MOZ_ASSERT(i < mArgc || paramInfo.IsOptional(),
+                   "Expected either enough arguments or an optional argument");
+        if (i < mArgc)
+            src = mArgv[i];
+        else if (type_tag == nsXPTType::T_JSVAL)
+            src.setUndefined();
+        else
+            src.setNull();
+    }
+
+    nsID param_iid;
+    if (type_tag == nsXPTType::T_INTERFACE &&
+        NS_FAILED(mIFaceInfo->GetIIDForParamNoAlloc(mVTableIndex, &paramInfo,
+                                                    &param_iid))) {
+        ThrowBadParam(NS_ERROR_XPC_CANT_GET_PARAM_IFACE_INFO, i, mCallContext);
+        return false;
+    }
+
+    // Don't allow CPOWs to be passed to native code (in case they try to cast
+    // to a concrete type).
+    if (src.isObject() &&
+        jsipc::IsWrappedCPOW(&src.toObject()) &&
+        type_tag == nsXPTType::T_INTERFACE &&
+        !param_iid.Equals(NS_GET_IID(nsISupports)))
+    {
+        // Allow passing CPOWs to XPCWrappedJS.
+        nsCOMPtr<nsIXPConnectWrappedJS> wrappedJS(do_QueryInterface(mCallee));
+        if (!wrappedJS) {
+            ThrowBadParam(NS_ERROR_XPC_CANT_PASS_CPOW_TO_NATIVE, i, mCallContext);
+            return false;
+        }
+    }
+
+    nsresult err;
+    if (!XPCConvert::JSData2Native(&dp->val, src, type, &param_iid, &err)) {
+        ThrowBadParam(err, i, mCallContext);
+        return false;
+    }
+
+    return true;
+}
+
+bool
+CallMethodHelper::ConvertDependentParams()
+{
+    const uint8_t paramCount = mMethodInfo->GetParamCount();
+    for (uint8_t i = 0; i < paramCount; i++) {
+        const nsXPTParamInfo& paramInfo = mMethodInfo->GetParam(i);
+
+        if (!paramInfo.GetType().IsDependent())
+            continue;
+        if (!ConvertDependentParam(i))
+            return false;
+    }
+
+    return true;
+}
+
+bool
+CallMethodHelper::ConvertDependentParam(uint8_t i)
+{
+    const nsXPTParamInfo& paramInfo = mMethodInfo->GetParam(i);
+    const nsXPTType& type = paramInfo.GetType();
+    nsXPTType datum_type;
+    uint32_t array_count = 0;
+    bool isArray = type.IsArray();
+
+    bool isSizedString = isArray ?
+        false :
+        type.TagPart() == nsXPTType::T_PSTRING_SIZE_IS ||
+        type.TagPart() == nsXPTType::T_PWSTRING_SIZE_IS;
+
+    nsXPTCVariant* dp = GetDispatchParam(i);
+    dp->type = type;
+
+    if (isArray) {
+        if (NS_FAILED(mIFaceInfo->GetTypeForParam(mVTableIndex, &paramInfo, 1,
+                                                  &datum_type))) {
+            Throw(NS_ERROR_XPC_CANT_GET_ARRAY_INFO, mCallContext);
+            return false;
+        }
+        MOZ_ASSERT(datum_type.TagPart() != nsXPTType::T_JSVAL,
+                   "Arrays of JSVals not currently supported - see bug 693337.");
+    } else {
+        datum_type = type;
+    }
+
+    // Specify the correct storage/calling semantics.
+    if (paramInfo.IsIndirect())
+        dp->SetIndirect();
+
+    // We have 3 possible type of dependent parameters: Arrays, Sized Strings,
+    // and iid_is Interface pointers. The latter two always need cleanup, and
+    // arrays need cleanup for all non-arithmetic types. Since the latter two
+    // cases also happen to be non-arithmetic, we can just inspect datum_type
+    // here.
+    if (!datum_type.IsArithmetic())
+        dp->SetValNeedsCleanup();
+
+    // Even if there's nothing to convert, we still need to examine the
+    // JSObject container for out-params. If it's null or otherwise invalid,
+    // we want to know before the call, rather than after.
+    //
+    // This is a no-op for 'in' params.
+    RootedValue src(mCallContext);
+    if (!GetOutParamSource(i, &src))
+        return false;
+
+    // All that's left to do is value conversion. Bail early if we don't need
+    // to do that.
+    if (!paramInfo.IsIn())
+        return true;
+
+    // We're definitely some variety of 'in' now, so there's something to
+    // convert. The source value for conversion depends on whether we're
+    // dealing with an 'in' or an 'inout' parameter. 'inout' was handled above,
+    // so all that's left is 'in'.
+    if (!paramInfo.IsOut()) {
+        // Handle the 'in' case.
+        MOZ_ASSERT(i < mArgc || paramInfo.IsOptional(),
+                     "Expected either enough arguments or an optional argument");
+        src = i < mArgc ? mArgv[i] : JS::NullValue();
+    }
+
+    nsID param_iid;
+    if (datum_type.IsInterfacePointer() &&
+        !GetInterfaceTypeFromParam(i, datum_type, &param_iid))
+        return false;
+
+    nsresult err;
+
+    if (isArray || isSizedString) {
+        if (!GetArraySizeFromParam(i, src, &array_count))
+            return false;
+
+        if (isArray) {
+            if (array_count &&
+                !XPCConvert::JSArray2Native((void**)&dp->val, src,
+                                            array_count, datum_type, &param_iid,
+                                            &err)) {
+                // XXX need exception scheme for arrays to indicate bad element
+                ThrowBadParam(err, i, mCallContext);
+                return false;
+            }
+        } else // if (isSizedString)
+        {
+            if (!XPCConvert::JSStringWithSize2Native((void*)&dp->val,
+                                                     src, array_count,
+                                                     datum_type, &err)) {
+                ThrowBadParam(err, i, mCallContext);
+                return false;
+            }
+        }
+    } else {
+        if (!XPCConvert::JSData2Native(&dp->val, src, type,
+                                       &param_iid, &err)) {
+            ThrowBadParam(err, i, mCallContext);
+            return false;
+        }
+    }
+
+    return true;
+}
+
+// Performs all necessary teardown on a parameter after method invocation.
+//
+// This method should only be called if the value in question was flagged
+// for cleanup (ie, if dp->DoesValNeedCleanup()).
+void
+CallMethodHelper::CleanupParam(nsXPTCMiniVariant& param, nsXPTType& type)
+{
+    // We handle array elements, but not the arrays themselves.
+    MOZ_ASSERT(type.TagPart() != nsXPTType::T_ARRAY, "Can't handle arrays.");
+
+    // Pointers may sometimes be null even if cleanup was requested. Combine
+    // the null checking for all the different types into one check here.
+    if (type.TagPart() != nsXPTType::T_JSVAL && param.val.p == nullptr)
+        return;
+
+    switch (type.TagPart()) {
+        case nsXPTType::T_JSVAL:
+            js::RemoveRawValueRoot(mCallContext, (Value*)&param.val);
+            break;
+        case nsXPTType::T_INTERFACE:
+        case nsXPTType::T_INTERFACE_IS:
+            ((nsISupports*)param.val.p)->Release();
+            break;
+        case nsXPTType::T_ASTRING:
+        case nsXPTType::T_DOMSTRING:
+            nsXPConnect::GetContextInstance()->mScratchStrings.Destroy((nsString*)param.val.p);
+            break;
+        case nsXPTType::T_UTF8STRING:
+        case nsXPTType::T_CSTRING:
+            nsXPConnect::GetContextInstance()->mScratchCStrings.Destroy((nsCString*)param.val.p);
+            break;
+        default:
+            MOZ_ASSERT(!type.IsArithmetic(), "Cleanup requested on unexpected type.");
+            free(param.val.p);
+            break;
+    }
+}
+
+bool
+CallMethodHelper::AllocateStringClass(nsXPTCVariant* dp,
+                                      const nsXPTParamInfo& paramInfo)
+{
+    // Get something we can make comparisons with.
+    uint8_t type_tag = paramInfo.GetType().TagPart();
+
+    // There should be 4 cases, all strings. Verify that here.
+    MOZ_ASSERT(type_tag == nsXPTType::T_ASTRING ||
+               type_tag == nsXPTType::T_DOMSTRING ||
+               type_tag == nsXPTType::T_UTF8STRING ||
+               type_tag == nsXPTType::T_CSTRING,
+               "Unexpected string class type!");
+
+    // ASTRING and DOMSTRING are very similar, and both use nsString.
+    // UTF8_STRING and CSTRING are also quite similar, and both use nsCString.
+    if (type_tag == nsXPTType::T_ASTRING || type_tag == nsXPTType::T_DOMSTRING)
+        dp->val.p = nsXPConnect::GetContextInstance()->mScratchStrings.Create();
+    else
+        dp->val.p = nsXPConnect::GetContextInstance()->mScratchCStrings.Create();
+
+    // Check for OOM, in either case.
+    if (!dp->val.p) {
+        JS_ReportOutOfMemory(mCallContext);
+        return false;
+    }
+
+    // We allocated, so we need to deallocate after the method call completes.
+    dp->SetValNeedsCleanup();
+
+    return true;
+}
+
+nsresult
+CallMethodHelper::Invoke()
+{
+    uint32_t argc = mDispatchParams.Length();
+    nsXPTCVariant* argv = mDispatchParams.Elements();
+
+    return NS_InvokeByIndex(mCallee, mVTableIndex, argc, argv);
+}
+
+/***************************************************************************/
+// interface methods
+
+JSObject*
+XPCWrappedNative::GetJSObject()
+{
+    return GetFlatJSObject();
+}
+
+NS_IMETHODIMP XPCWrappedNative::GetNative(nsISupports * *aNative)
+{
+    // No need to QI here, we already have the correct nsISupports
+    // vtable.
+    nsCOMPtr<nsISupports> rval = mIdentity;
+    rval.forget(aNative);
+    return NS_OK;
+}
+
+NS_IMETHODIMP XPCWrappedNative::GetJSObjectPrototype(JSObject * *aJSObjectPrototype)
+{
+    *aJSObjectPrototype = HasProto() ?
+                GetProto()->GetJSProtoObject() : GetFlatJSObject();
+    return NS_OK;
+}
+
+nsIPrincipal*
+XPCWrappedNative::GetObjectPrincipal() const
+{
+    nsIPrincipal* principal = GetScope()->GetPrincipal();
+#ifdef DEBUG
+    // Because of inner window reuse, we can have objects with one principal
+    // living in a scope with a different (but same-origin) principal. So
+    // just check same-origin here.
+    nsCOMPtr<nsIScriptObjectPrincipal> objPrin(do_QueryInterface(mIdentity));
+    if (objPrin) {
+        bool equal;
+        if (!principal)
+            equal = !objPrin->GetPrincipal();
+        else
+            principal->Equals(objPrin->GetPrincipal(), &equal);
+        MOZ_ASSERT(equal, "Principal mismatch.  Expect bad things to happen");
+    }
+#endif
+    return principal;
+}
+
+NS_IMETHODIMP XPCWrappedNative::FindInterfaceWithMember(HandleId name,
+                                                        nsIInterfaceInfo * *_retval)
+{
+    RefPtr<XPCNativeInterface> iface;
+    XPCNativeMember*  member;
+
+    if (GetSet()->FindMember(name, &member, &iface) && iface) {
+        nsCOMPtr<nsIInterfaceInfo> temp = iface->GetInterfaceInfo();
+        temp.forget(_retval);
+    } else
+        *_retval = nullptr;
+    return NS_OK;
+}
+
+NS_IMETHODIMP XPCWrappedNative::FindInterfaceWithName(HandleId name,
+                                                      nsIInterfaceInfo * *_retval)
+{
+    XPCNativeInterface* iface = GetSet()->FindNamedInterface(name);
+    if (iface) {
+        nsCOMPtr<nsIInterfaceInfo> temp = iface->GetInterfaceInfo();
+        temp.forget(_retval);
+    } else
+        *_retval = nullptr;
+    return NS_OK;
+}
+
+NS_IMETHODIMP_(bool)
+XPCWrappedNative::HasNativeMember(HandleId name)
+{
+    XPCNativeMember* member = nullptr;
+    uint16_t ignored;
+    return GetSet()->FindMember(name, &member, &ignored) && !!member;
+}
+
+NS_IMETHODIMP XPCWrappedNative::DebugDump(int16_t depth)
+{
+#ifdef DEBUG
+    depth-- ;
+    XPC_LOG_ALWAYS(("XPCWrappedNative @ %x with mRefCnt = %d", this, mRefCnt.get()));
+    XPC_LOG_INDENT();
+
+        if (HasProto()) {
+            XPCWrappedNativeProto* proto = GetProto();
+            if (depth && proto)
+                proto->DebugDump(depth);
+            else
+                XPC_LOG_ALWAYS(("mMaybeProto @ %x", proto));
+        } else
+            XPC_LOG_ALWAYS(("Scope @ %x", GetScope()));
+
+        if (depth && mSet)
+            mSet->DebugDump(depth);
+        else
+            XPC_LOG_ALWAYS(("mSet @ %x", mSet.get()));
+
+        XPC_LOG_ALWAYS(("mFlatJSObject of %x", mFlatJSObject.unbarrieredGetPtr()));
+        XPC_LOG_ALWAYS(("mIdentity of %x", mIdentity.get()));
+        XPC_LOG_ALWAYS(("mScriptableInfo @ %x", mScriptableInfo));
+
+        if (depth && mScriptableInfo) {
+            XPC_LOG_INDENT();
+            XPC_LOG_ALWAYS(("mScriptable @ %x", mScriptableInfo->GetCallback()));
+            XPC_LOG_ALWAYS(("mFlags of %x", (uint32_t)mScriptableInfo->GetFlags()));
+            XPC_LOG_ALWAYS(("mJSClass @ %x", mScriptableInfo->GetJSClass()));
+            XPC_LOG_OUTDENT();
+        }
+    XPC_LOG_OUTDENT();
+#endif
+    return NS_OK;
+}
+
+/***************************************************************************/
+
+char*
+XPCWrappedNative::ToString(XPCWrappedNativeTearOff* to /* = nullptr */ ) const
+{
+#ifdef DEBUG
+#  define FMT_ADDR " @ 0x%p"
+#  define FMT_STR(str) str
+#  define PARAM_ADDR(w) , w
+#else
+#  define FMT_ADDR ""
+#  define FMT_STR(str)
+#  define PARAM_ADDR(w)
+#endif
+
+    char* sz = nullptr;
+    char* name = nullptr;
+
+    XPCNativeScriptableInfo* si = GetScriptableInfo();
+    if (si)
+        name = JS_smprintf("%s", si->GetJSClass()->name);
+    if (to) {
+        const char* fmt = name ? " (%s)" : "%s";
+        name = JS_sprintf_append(name, fmt,
+                                 to->GetInterface()->GetNameString());
+    } else if (!name) {
+        XPCNativeSet* set = GetSet();
+        XPCNativeInterface** array = set->GetInterfaceArray();
+        RefPtr<XPCNativeInterface> isupp = XPCNativeInterface::GetISupports();
+        uint16_t count = set->GetInterfaceCount();
+
+        if (count == 1)
+            name = JS_sprintf_append(name, "%s", array[0]->GetNameString());
+        else if (count == 2 && array[0] == isupp) {
+            name = JS_sprintf_append(name, "%s", array[1]->GetNameString());
+        } else {
+            for (uint16_t i = 0; i < count; i++) {
+                const char* fmt = (i == 0) ?
+                                    "(%s" : (i == count-1) ?
+                                        ", %s)" : ", %s";
+                name = JS_sprintf_append(name, fmt,
+                                         array[i]->GetNameString());
+            }
+        }
+    }
+
+    if (!name) {
+        return nullptr;
+    }
+    const char* fmt = "[xpconnect wrapped %s" FMT_ADDR FMT_STR(" (native")
+        FMT_ADDR FMT_STR(")") "]";
+    if (si) {
+        fmt = "[object %s" FMT_ADDR FMT_STR(" (native") FMT_ADDR FMT_STR(")") "]";
+    }
+    sz = JS_smprintf(fmt, name PARAM_ADDR(this) PARAM_ADDR(mIdentity.get()));
+
+    JS_smprintf_free(name);
+
+
+    return sz;
+
+#undef FMT_ADDR
+#undef PARAM_ADDR
+}
+
+/***************************************************************************/
+
+#ifdef XPC_CHECK_CLASSINFO_CLAIMS
+static void DEBUG_CheckClassInfoClaims(XPCWrappedNative* wrapper)
+{
+    if (!wrapper || !wrapper->GetClassInfo())
+        return;
+
+    nsISupports* obj = wrapper->GetIdentityObject();
+    XPCNativeSet* set = wrapper->GetSet();
+    uint16_t count = set->GetInterfaceCount();
+    for (uint16_t i = 0; i < count; i++) {
+        nsIClassInfo* clsInfo = wrapper->GetClassInfo();
+        XPCNativeInterface* iface = set->GetInterfaceAt(i);
+        nsIInterfaceInfo* info = iface->GetInterfaceInfo();
+        const nsIID* iid;
+        nsISupports* ptr;
+
+        info->GetIIDShared(&iid);
+        nsresult rv = obj->QueryInterface(*iid, (void**)&ptr);
+        if (NS_SUCCEEDED(rv)) {
+            NS_RELEASE(ptr);
+            continue;
+        }
+        if (rv == NS_ERROR_OUT_OF_MEMORY)
+            continue;
+
+        // Houston, We have a problem...
+
+        char* className = nullptr;
+        char* contractID = nullptr;
+        const char* interfaceName;
+
+        info->GetNameShared(&interfaceName);
+        clsInfo->GetContractID(&contractID);
+        if (wrapper->GetScriptableInfo()) {
+            wrapper->GetScriptableInfo()->GetCallback()->
+                GetClassName(&className);
+        }
+
+
+        printf("\n!!! Object's nsIClassInfo lies about its interfaces!!!\n"
+               "   classname: %s \n"
+               "   contractid: %s \n"
+               "   unimplemented interface name: %s\n\n",
+               className ? className : "<unknown>",
+               contractID ? contractID : "<unknown>",
+               interfaceName);
+
+        if (className)
+            free(className);
+        if (contractID)
+            free(contractID);
+    }
+}
+#endif
+
+NS_IMPL_ISUPPORTS(XPCJSObjectHolder, nsIXPConnectJSObjectHolder)
+
+JSObject*
+XPCJSObjectHolder::GetJSObject()
+{
+    NS_PRECONDITION(mJSObj, "bad object state");
+    return mJSObj;
+}
+
+XPCJSObjectHolder::XPCJSObjectHolder(JSObject* obj)
+    : mJSObj(obj)
+{
+    MOZ_ASSERT(obj);
+    XPCJSContext::Get()->AddObjectHolderRoot(this);
+}
+
+XPCJSObjectHolder::~XPCJSObjectHolder()
+{
+    RemoveFromRootSet();
+}
+
+void
+XPCJSObjectHolder::TraceJS(JSTracer* trc)
+{
+    JS::TraceEdge(trc, &mJSObj, "XPCJSObjectHolder::mJSObj");
+}