Bug 1210517 - Create nsVariant directly rather than via do_CreateInstance(). r=froydnj

The goal here is to leave creation stuff mostly for JS, so we can
convert it entirely over to a non-threadsafe cycle-collected version
without breaking any existing C++ users.

I didn't do this for a remaining use in nsGlobalWindow.h to avoid
including nsVariant.h all over the place.

dom/base/nsContentAreaDragDrop.cpp

@@ -57,6 +57,7 @@
 #include "TabParent.h"
 #include "mozilla/dom/Element.h"
 #include "mozilla/dom/HTMLAreaElement.h"
+#include "nsVariant.h"
 
 using namespace mozilla::dom;
 
@@ -726,11 +727,9 @@ DragDataProducer::AddString(DataTransfer* aDataTransfer,
                             const nsAString& aData,
                             nsIPrincipal* aPrincipal)
 {
-  nsCOMPtr<nsIWritableVariant> variant = do_CreateInstance(NS_VARIANT_CONTRACTID);
-  if (variant) {
-    variant->SetAsAString(aData);
-    aDataTransfer->SetDataWithPrincipal(aFlavor, variant, 0, aPrincipal);
-  }
+  nsRefPtr<nsVariant> variant = new nsVariant();
+  variant->SetAsAString(aData);
+  aDataTransfer->SetDataWithPrincipal(aFlavor, variant, 0, aPrincipal);
 }
 
 nsresult
@@ -784,12 +783,10 @@ DragDataProducer::AddStringsToDataTransfer(nsIContent* aDragNode,
   // a new flavor so as not to confuse anyone who is really registered
   // for image/gif or image/jpg.
   if (mImage) {
-    nsCOMPtr<nsIWritableVariant> variant = do_CreateInstance(NS_VARIANT_CONTRACTID);
-    if (variant) {
-      variant->SetAsISupports(mImage);
-      aDataTransfer->SetDataWithPrincipal(NS_LITERAL_STRING(kNativeImageMime),
-                                          variant, 0, principal);
-    }
+    nsRefPtr<nsVariant> variant = new nsVariant();
+    variant->SetAsISupports(mImage);
+    aDataTransfer->SetDataWithPrincipal(NS_LITERAL_STRING(kNativeImageMime),
+                                        variant, 0, principal);
 
     // assume the image comes from a file, and add a file promise. We
     // register ourselves as a nsIFlavorDataProvider, and will use the
@@ -798,12 +795,10 @@ DragDataProducer::AddStringsToDataTransfer(nsIContent* aDragNode,
     nsCOMPtr<nsIFlavorDataProvider> dataProvider =
       new nsContentAreaDragDropDataProvider();
     if (dataProvider) {
-      nsCOMPtr<nsIWritableVariant> variant = do_CreateInstance(NS_VARIANT_CONTRACTID);
-      if (variant) {
-        variant->SetAsISupports(dataProvider);
-        aDataTransfer->SetDataWithPrincipal(NS_LITERAL_STRING(kFilePromiseMime),
-                                            variant, 0, principal);
-      }
+      nsRefPtr<nsVariant> variant = new nsVariant();
+      variant->SetAsISupports(dataProvider);
+      aDataTransfer->SetDataWithPrincipal(NS_LITERAL_STRING(kFilePromiseMime),
+                                          variant, 0, principal);
     }
 
     AddString(aDataTransfer, NS_LITERAL_STRING(kFilePromiseURLMime),

dom/events/DataTransfer.cpp

@@ -10,7 +10,6 @@
 #include "DataTransfer.h"
 
 #include "nsIDOMDocument.h"
-#include "nsIVariant.h"
 #include "nsISupportsPrimitives.h"
 #include "nsIScriptSecurityManager.h"
 #include "mozilla/dom/DOMStringList.h"
@@ -24,6 +23,7 @@
 #include "nsIScriptContext.h"
 #include "nsIDocument.h"
 #include "nsIScriptGlobalObject.h"
+#include "nsVariant.h"
 #include "mozilla/dom/ContentChild.h"
 #include "mozilla/dom/DataTransferBinding.h"
 #include "mozilla/dom/Directory.h"
@@ -435,12 +435,7 @@ void
 DataTransfer::SetData(const nsAString& aFormat, const nsAString& aData,
                       ErrorResult& aRv)
 {
-  nsCOMPtr<nsIWritableVariant> variant = do_CreateInstance(NS_VARIANT_CONTRACTID);
-  if (!variant) {
-    aRv.Throw(NS_ERROR_OUT_OF_MEMORY);
-    return;
-  }
-
+  nsRefPtr<nsVariant> variant = new nsVariant();
   variant->SetAsAString(aData);
 
   aRv = MozSetDataAt(aFormat, variant, 0);
@@ -1350,9 +1345,7 @@ DataTransfer::FillInExternalData(TransferItem& aItem, uint32_t aIndex)
     if (!data)
       return;
 
-    nsCOMPtr<nsIWritableVariant> variant = do_CreateInstance(NS_VARIANT_CONTRACTID);
-    if (!variant)
-      return;
+    nsRefPtr<nsVariant> variant = new nsVariant();
 
     nsCOMPtr<nsISupportsString> supportsstr = do_QueryInterface(data);
     if (supportsstr) {

dom/html/HTMLInputElement.cpp

@@ -63,6 +63,7 @@
 #include "nsReadableUtils.h"
 #include "nsUnicharUtils.h"
 #include "nsLayoutUtils.h"
+#include "nsVariant.h"
 
 #include "nsIDOMMutationEvent.h"
 #include "mozilla/ContentEvents.h"
@@ -807,9 +808,7 @@ UploadLastDir::StoreLastUsedDirectory(nsIDocument* aDoc, nsIFile* aDir)
   aDir->GetPath(unicodePath);
   if (unicodePath.IsEmpty()) // nothing to do
     return NS_OK;
-  nsCOMPtr<nsIWritableVariant> prefValue = do_CreateInstance(NS_VARIANT_CONTRACTID);
-  if (!prefValue)
-    return NS_ERROR_OUT_OF_MEMORY;
+  nsRefPtr<nsVariant> prefValue = new nsVariant();
   prefValue->SetAsAString(unicodePath);
 
   // Use the document's current load context to ensure that the content pref

dom/html/TextTrackManager.cpp

@@ -13,6 +13,7 @@
 #include "mozilla/dom/Event.h"
 #include "mozilla/ClearOnShutdown.h"
 #include "nsComponentManagerUtils.h"
+#include "nsVariant.h"
 #include "nsVideoFrame.h"
 #include "nsIFrame.h"
 #include "nsTArrayHelpers.h"
@@ -214,8 +215,7 @@ TextTrackManager::UpdateCueDisplay()
   mTextTracks->UpdateAndGetShowingCues(activeCues);
 
   if (activeCues.Length() > 0) {
-    nsCOMPtr<nsIWritableVariant> jsCues =
-      do_CreateInstance("@mozilla.org/variant;1");
+    nsRefPtr<nsVariant> jsCues = new nsVariant();
 
     jsCues->SetAsArray(nsIDataType::VTYPE_INTERFACE,
                        &NS_GET_IID(nsIDOMEventTarget),

dom/ipc/ContentChild.cpp

@@ -85,6 +85,7 @@
 #include "nsMemoryInfoDumper.h"
 #include "nsServiceManagerUtils.h"
 #include "nsStyleSheetService.h"
+#include "nsVariant.h"
 #include "nsXULAppAPI.h"
 #include "nsIScriptError.h"
 #include "nsIConsoleService.h"
@@ -2864,9 +2865,7 @@ ContentChild::RecvInvokeDragSession(nsTArray<IPCDataTransfer>&& aTransfers,
         auto& items = aTransfers[i].items();
         for (uint32_t j = 0; j < items.Length(); ++j) {
           const IPCDataTransferItem& item = items[j];
-          nsCOMPtr<nsIWritableVariant> variant =
-             do_CreateInstance(NS_VARIANT_CONTRACTID);
-          NS_ENSURE_TRUE(variant, false);
+          nsRefPtr<nsVariant> variant = new nsVariant();
           if (item.data().type() == IPCDataTransferData::TnsString) {
             const nsString& data = item.data().get_nsString();
             variant->SetAsAString(data);

dom/ipc/TabParent.cpp

@@ -63,6 +63,7 @@
 #include "nsIXULWindow.h"
 #include "nsIRemoteBrowser.h"
 #include "nsViewManager.h"
+#include "nsVariant.h"
 #include "nsIWidget.h"
 #include "nsIWindowMediator.h"
 #include "nsIWindowWatcher.h"
@@ -3541,7 +3542,7 @@ TabParent::RecvInvokeDragSession(nsTArray<IPCDataTransfer>&& aTransfers,
   }
   mDragAreaX = aDragAreaX;
   mDragAreaY = aDragAreaY;
-  
+
   esm->BeginTrackingRemoteDragGesture(mFrameElement);
 
   return true;
@@ -3554,11 +3555,7 @@ TabParent::AddInitialDnDDataTo(DataTransfer* aDataTransfer)
     nsTArray<DataTransferItem>& itemArray = mInitialDataTransferItems[i];
     for (uint32_t j = 0; j < itemArray.Length(); ++j) {
       DataTransferItem& item = itemArray[j];
-      nsCOMPtr<nsIWritableVariant> variant =
-        do_CreateInstance(NS_VARIANT_CONTRACTID);
-      if (!variant) {
-        break;
-      }
+      nsRefPtr<nsVariant> variant = new nsVariant();
       // Special case kFilePromiseMime so that we get the right
       // nsIFlavorDataProvider for it.
       if (item.mFlavor.EqualsLiteral(kFilePromiseMime)) {

dom/media/MediaManager.cpp

@@ -50,6 +50,7 @@
 #include "Latency.h"
 #include "nsProxyRelease.h"
 #include "nsNullPrincipal.h"
+#include "nsVariant.h"
 
 // For PR_snprintf
 #include "prprf.h"
@@ -2203,7 +2204,7 @@ MediaManager::AnonymizeId(nsAString& aId, const nsACString& aOriginKey)
 already_AddRefed<nsIWritableVariant>
 MediaManager::ToJSArray(SourceSet& aDevices)
 {
-  nsCOMPtr<nsIWritableVariant> var = do_CreateInstance("@mozilla.org/variant;1");
+  nsRefPtr<nsVariant> var = new nsVariant();
   size_t len = aDevices.Length();
   if (len) {
     nsTArray<nsIMediaDevice*> tmp(len);

dom/mobilemessage/DeletedMessageInfo.cpp

@@ -69,10 +69,9 @@ DeletedMessageInfo::GetDeletedMessageIds(nsIVariant** aDeletedMessageIds)
     return NS_OK;
   }
 
-  nsresult rv;
-  mDeletedMessageIds = do_CreateInstance(NS_VARIANT_CONTRACTID, &rv);
-  NS_ENSURE_SUCCESS(rv, rv);
+  mDeletedMessageIds = new nsVariant();
 
+  nsresult rv;
   rv = mDeletedMessageIds->SetAsArray(nsIDataType::VTYPE_INT32,
                                       nullptr,
                                       length,
@@ -103,10 +102,9 @@ DeletedMessageInfo::GetDeletedThreadIds(nsIVariant** aDeletedThreadIds)
     return NS_OK;
   }
 
-  nsresult rv;
-  mDeletedThreadIds = do_CreateInstance(NS_VARIANT_CONTRACTID, &rv);
-  NS_ENSURE_SUCCESS(rv, rv);
+  mDeletedThreadIds = new nsVariant();
 
+  nsresult rv;
   rv = mDeletedThreadIds->SetAsArray(nsIDataType::VTYPE_UINT64,
                                      nullptr,
                                      length,

dom/storage/DOMStorageDBThread.cpp

@@ -20,7 +20,7 @@
 #include "mozIStorageValueArray.h"
 #include "mozIStorageFunction.h"
 #include "nsIObserverService.h"
-#include "nsIVariant.h"
+#include "nsVariant.h"
 #include "mozilla/IOInterposer.h"
 #include "mozilla/Services.h"
 
@@ -403,10 +403,7 @@ nsReverseStringSQLFunction::OnFunctionCall(
   nsAutoCString result;
   ReverseString(stringToReverse, result);
 
-  nsCOMPtr<nsIWritableVariant> outVar(do_CreateInstance(
-      NS_VARIANT_CONTRACTID, &rv));
-  NS_ENSURE_SUCCESS(rv, rv);
-
+  nsRefPtr<nsVariant> outVar(new nsVariant());
   rv = outVar->SetAsAUTF8String(result);
   NS_ENSURE_SUCCESS(rv, rv);
 

dom/system/gonk/mozstumbler/UploadStumbleRunnable.cpp

@@ -10,9 +10,9 @@
 #include "nsIInputStream.h"
 #include "nsIScriptSecurityManager.h"
 #include "nsIURLFormatter.h"
-#include "nsIVariant.h"
 #include "nsIXMLHttpRequest.h"
 #include "nsNetUtil.h"
+#include "nsVariant.h"
 
 UploadStumbleRunnable::UploadStumbleRunnable(nsIInputStream* aUploadData)
 : mUploadInputStream(aUploadData)
@@ -34,8 +34,7 @@ nsresult
 UploadStumbleRunnable::Upload()
 {
   nsresult rv;
-  nsCOMPtr<nsIWritableVariant> variant = do_CreateInstance("@mozilla.org/variant;1", &rv);
-  NS_ENSURE_SUCCESS(rv, rv);
+  nsRefPtr<nsVariant> variant = new nsVariant();
 
   rv = variant->SetAsISupports(mUploadInputStream);
   NS_ENSURE_SUCCESS(rv, rv);

dom/workers/XMLHttpRequest.cpp

@@ -9,7 +9,6 @@
 #include "nsIDOMEvent.h"
 #include "nsIDOMEventListener.h"
 #include "nsIRunnable.h"
-#include "nsIVariant.h"
 #include "nsIXMLHttpRequest.h"
 #include "nsIXPConnect.h"
 
@@ -24,6 +23,7 @@
 #include "nsFormData.h"
 #include "nsJSUtils.h"
 #include "nsThreadUtils.h"
+#include "nsVariant.h"
 
 #include "RuntimeService.h"
 #include "WorkerPrivate.h"
@@ -1527,9 +1527,7 @@ SendRunnable::MainThreadRun()
     }
   }
   else {
-    nsCOMPtr<nsIWritableVariant> wvariant =
-      do_CreateInstance(NS_VARIANT_CONTRACTID);
-    NS_ENSURE_TRUE(wvariant, NS_ERROR_UNEXPECTED);
+    nsRefPtr<nsVariant> wvariant = new nsVariant();
 
     if (NS_FAILED(wvariant->SetAsAString(mStringBody))) {
       MOZ_ASSERT(false, "This should never fail!");

dom/xslt/xslt/txMozillaXSLTProcessor.cpp

@@ -34,6 +34,7 @@
 #include "nsIScriptSecurityManager.h"
 #include "nsJSUtils.h"
 #include "nsIXPConnect.h"
+#include "nsVariant.h"
 #include "mozilla/dom/DocumentFragment.h"
 #include "mozilla/dom/XSLTProcessorBinding.h"
 
@@ -845,9 +846,7 @@ txMozillaXSLTProcessor::SetParameter(const nsAString & aNamespaceURI,
                 rv = xpathResult->Clone(getter_AddRefs(clone));
                 NS_ENSURE_SUCCESS(rv, rv);
 
-                nsCOMPtr<nsIWritableVariant> variant =
-                    do_CreateInstance("@mozilla.org/variant;1", &rv);
-                NS_ENSURE_SUCCESS(rv, rv);
+                nsRefPtr<nsVariant> variant = new nsVariant();
 
                 rv = variant->SetAsISupports(clone);
                 NS_ENSURE_SUCCESS(rv, rv);

dom/xul/templates/nsXULTemplateQueryProcessorStorage.cpp

@@ -9,7 +9,7 @@
 #include "nsUnicharUtils.h"
 
 #include "nsArrayUtils.h"
-#include "nsIVariant.h"
+#include "nsVariant.h"
 #include "nsAppDirectoryServiceDefs.h"
 
 #include "nsIURI.h"
@@ -110,7 +110,7 @@ nsXULTemplateResultSetStorage::FillColumnValues(nsCOMArray<nsIVariant>& aArray)
     int32_t count = mColumnNames.Count();
 
     for (int32_t c = 0; c < count; c++) {
-        nsCOMPtr<nsIWritableVariant> value = do_CreateInstance("@mozilla.org/variant;1");
+        nsRefPtr<nsVariant> value = new nsVariant();
 
         int32_t type;
         mStatement->GetTypeOfIndex(c, &type);

editor/composer/nsEditorSpellCheck.cpp

@@ -35,7 +35,7 @@
 #include "nsITextServicesDocument.h"    // for nsITextServicesDocument
 #include "nsITextServicesFilter.h"      // for nsITextServicesFilter
 #include "nsIURI.h"                     // for nsIURI
-#include "nsIVariant.h"                 // for nsIWritableVariant, etc
+#include "nsVariant.h"                  // for nsIWritableVariant, etc
 #include "nsLiteralString.h"            // for NS_LITERAL_STRING, etc
 #include "nsMemory.h"                   // for nsMemory
 #include "nsRange.h"
@@ -201,8 +201,7 @@ StoreCurrentDictionary(nsIEditor* aEditor, const nsAString& aDictionary)
   rv = docUri->GetSpec(docUriSpec);
   NS_ENSURE_SUCCESS(rv, rv);
 
-  nsCOMPtr<nsIWritableVariant> prefValue = do_CreateInstance(NS_VARIANT_CONTRACTID);
-  NS_ENSURE_TRUE(prefValue, NS_ERROR_OUT_OF_MEMORY);
+  nsRefPtr<nsVariant> prefValue = new nsVariant();
   prefValue->SetAsAString(aDictionary);
 
   nsCOMPtr<nsIContentPrefService2> contentPrefService =

layout/xul/tree/nsTreeBodyFrame.cpp

@@ -44,6 +44,7 @@
 #include "nsContainerFrame.h"
 #include "nsView.h"
 #include "nsViewManager.h"
+#include "nsVariant.h"
 #include "nsWidgetsCID.h"
 #include "nsBoxFrame.h"
 #include "nsIURL.h"
@@ -4635,10 +4636,7 @@ nsTreeBodyFrame::FireRowCountChangedEvent(int32_t aIndex, int32_t aCount)
   // Set 'count' data - the number of changed rows.
   propBag->SetPropertyAsInt32(NS_LITERAL_STRING("count"), aCount);
 
-  nsCOMPtr<nsIWritableVariant> detailVariant(
-    do_CreateInstance("@mozilla.org/variant;1"));
-  if (!detailVariant)
-    return;
+  nsRefPtr<nsVariant> detailVariant(new nsVariant());
 
   detailVariant->SetAsISupports(propBag);
   treeEvent->InitCustomEvent(NS_LITERAL_STRING("TreeRowCountChanged"),
@@ -4707,10 +4705,7 @@ nsTreeBodyFrame::FireInvalidateEvent(int32_t aStartRowIdx, int32_t aEndRowIdx,
                                 endColIdx);
   }
 
-  nsCOMPtr<nsIWritableVariant> detailVariant(
-    do_CreateInstance("@mozilla.org/variant;1"));
-  if (!detailVariant)
-    return;
+  nsRefPtr<nsVariant> detailVariant(new nsVariant());
 
   detailVariant->SetAsISupports(propBag);
   treeEvent->InitCustomEvent(NS_LITERAL_STRING("TreeInvalidated"),

toolkit/components/places/Database.cpp

@@ -18,6 +18,7 @@
 #include "nsPlacesIndexes.h"
 #include "nsPlacesTriggers.h"
 #include "nsPlacesMacros.h"
+#include "nsVariant.h"
 #include "SQLFunctions.h"
 #include "Helpers.h"
 
@@ -420,9 +421,7 @@ NS_IMETHODIMP DatabaseShutdown::GetState(nsIPropertyBag** aState)
   if (NS_WARN_IF(NS_FAILED(rv))) return rv;
 
   // Put `mState` in field `progress`
-  nsCOMPtr<nsIWritableVariant> progress =
-    do_CreateInstance(NS_VARIANT_CONTRACTID, &rv);
-  if (NS_WARN_IF(NS_FAILED(rv))) return rv;
+  nsRefPtr<nsVariant> progress = new nsVariant();
 
   rv = progress->SetAsUint8(mState);
   if (NS_WARN_IF(NS_FAILED(rv))) return rv;
@@ -440,9 +439,7 @@ NS_IMETHODIMP DatabaseShutdown::GetState(nsIPropertyBag** aState)
     return NS_OK;
   }
 
-  nsCOMPtr<nsIWritableVariant> barrier =
-    do_CreateInstance(NS_VARIANT_CONTRACTID, &rv);
-  if (NS_WARN_IF(NS_FAILED(rv))) return rv;
+  nsRefPtr<nsVariant> barrier = new nsVariant();
 
   rv = barrier->SetAsInterface(NS_GET_IID(nsIPropertyBag), barrierState);
   if (NS_WARN_IF(NS_FAILED(rv))) return rv;

toolkit/components/places/SQLFunctions.cpp

@@ -16,6 +16,7 @@
 #include "nsPrintfCString.h"
 #include "nsNavHistory.h"
 #include "mozilla/Likely.h"
+#include "nsVariant.h"
 
 using namespace mozilla::storage;
 
@@ -703,9 +704,7 @@ namespace places {
     nsAutoString src;
     aArguments->GetString(0, src);
 
-    nsCOMPtr<nsIWritableVariant> result =
-      do_CreateInstance("@mozilla.org/variant;1");
-    NS_ENSURE_STATE(result);
+    nsRefPtr<nsVariant> result = new nsVariant();
 
     if (src.Length()>1) {
       src.Truncate(src.Length() - 1);
@@ -761,9 +760,7 @@ namespace places {
     nsAutoString src;
     aArguments->GetString(0, src);
 
-    nsCOMPtr<nsIWritableVariant> result =
-      do_CreateInstance("@mozilla.org/variant;1");
-    NS_ENSURE_STATE(result);
+    nsRefPtr<nsVariant> result = new nsVariant();
 
     if (StringBeginsWith(src, NS_LITERAL_STRING("http://")))
       src.Cut(0, 7);
@@ -835,9 +832,7 @@ namespace places {
     navHistory->DispatchFrecencyChangedNotification(spec, newFrecency, guid,
                                                     hidden, lastVisitDate);
 
-    nsCOMPtr<nsIWritableVariant> result =
-      do_CreateInstance("@mozilla.org/variant;1");
-    NS_ENSURE_STATE(result);
+    nsRefPtr<nsVariant> result = new nsVariant();
     rv = result->SetAsInt32(newFrecency);
     NS_ENSURE_SUCCESS(rv, rv);
     result.forget(_result);

toolkit/components/places/nsNavHistoryQuery.cpp

@@ -18,6 +18,7 @@
 #include "nsNetUtil.h"
 #include "nsTArray.h"
 #include "prprf.h"
+#include "nsVariant.h"
 
 using namespace mozilla;
 
@@ -1130,13 +1131,11 @@ NS_IMETHODIMP nsNavHistoryQuery::GetTags(nsIVariant **aTags)
 {
   NS_ENSURE_ARG_POINTER(aTags);
 
-  nsresult rv;
-  nsCOMPtr<nsIWritableVariant> out = do_CreateInstance(NS_VARIANT_CONTRACTID,
-                                                       &rv);
-  NS_ENSURE_SUCCESS(rv, rv);
+  nsRefPtr<nsVariant> out = new nsVariant();
 
   uint32_t arrayLen = mTags.Length();
 
+  nsresult rv;
   if (arrayLen == 0)
     rv = out->SetAsEmptyArray();
   else {

toolkit/xre/nsUpdateDriver.cpp

@@ -11,7 +11,7 @@
 #include "nsAppRunner.h"
 #include "nsIWritablePropertyBag.h"
 #include "nsIFile.h"
-#include "nsIVariant.h"
+#include "nsVariant.h"
 #include "nsCOMPtr.h"
 #include "nsString.h"
 #include "prproces.h"
@@ -691,12 +691,7 @@ SetOSApplyToDir(nsIUpdate* update, const nsACString& osApplyToDir)
     return;
   }
 
-  nsCOMPtr<nsIWritableVariant> variant =
-    do_CreateInstance("@mozilla.org/variant;1", &rv);
-  if (NS_FAILED(rv)) {
-    return;
-  }
-
+  nsRefPtr<nsVariant> variant = new nsVariant();
   rv = variant->SetAsACString(osApplyToDir);
   if (NS_FAILED(rv)) {
     return;

uriloader/exthandler/win/nsMIMEInfoWin.cpp

@@ -7,7 +7,6 @@
 #include "nsArrayEnumerator.h"
 #include "nsCOMArray.h"
 #include "nsIFile.h"
-#include "nsIVariant.h"
 #include "nsMIMEInfoWin.h"
 #include "nsNetUtil.h"
 #include <windows.h>
@@ -22,6 +21,7 @@
 #include "nsOSHelperAppService.h"
 #include "nsUnicharUtils.h"
 #include "nsITextToSubURI.h"
+#include "nsVariant.h"
 
 #define RUNDLL32_EXE L"\\rundll32.exe"
 
@@ -172,15 +172,13 @@ nsMIMEInfoWin::GetEnumerator(nsISimpleEnumerator* *_retval)
 
 static nsresult GetIconURLVariant(nsIFile* aApplication, nsIVariant* *_retval)
 {
-  nsresult rv = CallCreateInstance("@mozilla.org/variant;1", _retval);
-  if (NS_FAILED(rv))
-    return rv;
   nsAutoCString fileURLSpec;
   NS_GetURLSpecFromFile(aApplication, fileURLSpec);
   nsAutoCString iconURLSpec; iconURLSpec.AssignLiteral("moz-icon://");
   iconURLSpec += fileURLSpec;
-  nsCOMPtr<nsIWritableVariant> writable(do_QueryInterface(*_retval));
+  nsRefPtr<nsVariant> writable(new nsVariant());
   writable->SetAsAUTF8String(iconURLSpec);
+  writable.forget(_retval);
   return NS_OK;
 }