SkDocument: remove unused fDoneProc

Change-Id: I9a0739992e90a0a6d44a75b0b570097553343f1d
Reviewed-on: https://skia-review.googlesource.com/92141
Commit-Queue: Hal Canary <halcanary@google.com>
Reviewed-by: Ben Wagner <bungeman@google.com>
diff --git a/src/xps/SkXPSDocument.cpp b/src/xps/SkXPSDocument.cpp
index ac62c62..05bb280 100644
--- a/src/xps/SkXPSDocument.cpp
+++ b/src/xps/SkXPSDocument.cpp
@@ -16,7 +16,7 @@
 SkXPSDocument::SkXPSDocument(SkWStream* stream,
                    SkScalar dpi,
                    SkTScopedComPtr<IXpsOMObjectFactory> xpsFactory)
-        : SkDocument(stream, nullptr)
+        : SkDocument(stream)
         , fXpsFactory(std::move(xpsFactory))
         , fDevice(SkISize{10000, 10000})
 {