Track another orphan from CPWL_AppStream

Bug: chromium:956947
Change-Id: I7ade6c0b3f1cb9e0df50e14d772b601d1eee3845
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/53670
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Tom Sepez <tsepez@chromium.org>
diff --git a/fpdfsdk/pwl/cpwl_appstream.cpp b/fpdfsdk/pwl/cpwl_appstream.cpp
index 670bda6..fc1e6f1 100644
--- a/fpdfsdk/pwl/cpwl_appstream.cpp
+++ b/fpdfsdk/pwl/cpwl_appstream.cpp
@@ -1944,7 +1944,8 @@
 }
 
 void CPWL_AppStream::Remove(const ByteString& sAPType) {
-  dict_->RemoveFor(sAPType);
+  CPDF_Document* doc = widget_->GetPageView()->GetPDFDocument();
+  doc->AddOrphan(dict_->RemoveFor(sAPType));
 }
 
 ByteString CPWL_AppStream::GetBackgroundAppStream() const {