Fix potential leak. r=attinasi a=waterson

content/html/style/src/nsCSSLoader.cpp

@@ -1270,6 +1270,7 @@ CSSLoaderImpl::LoadSheet(URLKey& aKey, SheetLoadData* aData)
             if (NS_SUCCEEDED(result) && equals)
             {
               mPendingAlternateSheets.RemoveElementAt(index);
+              NS_IF_RELEASE(loadingData->mNext);
               loadingData->mNext = data;
               loadingData = data;
             }

layout/html/style/src/nsCSSLoader.cpp

@@ -1270,6 +1270,7 @@ CSSLoaderImpl::LoadSheet(URLKey& aKey, SheetLoadData* aData)
             if (NS_SUCCEEDED(result) && equals)
             {
               mPendingAlternateSheets.RemoveElementAt(index);
+              NS_IF_RELEASE(loadingData->mNext);
               loadingData->mNext = data;
               loadingData = data;
             }

layout/style/nsCSSLoader.cpp

@@ -1270,6 +1270,7 @@ CSSLoaderImpl::LoadSheet(URLKey& aKey, SheetLoadData* aData)
             if (NS_SUCCEEDED(result) && equals)
             {
               mPendingAlternateSheets.RemoveElementAt(index);
+              NS_IF_RELEASE(loadingData->mNext);
               loadingData->mNext = data;
               loadingData = data;
             }