DM: add --multiPage option

dm/DMSrcSink.h

Index: dm/DMSrcSink.h
diff --git a/dm/DMSrcSink.h b/dm/DMSrcSink.h
index 0807cb664454e173cfc3cc3d5848d2aac5f85d7d..65ab4a6d1c4ade846be0dc636237ab64884b724d 100644
--- a/dm/DMSrcSink.h
+++ b/dm/DMSrcSink.h
@@ -166,20 +166,26 @@ private:
 
 class PDFSink : public Sink {
 public:
-    PDFSink();
+    PDFSink(bool multiPage = false);
 
     Error draw(const Src&, SkBitmap*, SkWStream*, SkString*) const override;
     int enclave() const override { return kAnyThread_Enclave; }
     const char* fileExtension() const override { return "pdf"; }
+
+private:
+    bool fMultiPage;
 };
 
 class XPSSink : public Sink {
 public:
-    XPSSink();
+    XPSSink(bool multiPage = false);
 
     Error draw(const Src&, SkBitmap*, SkWStream*, SkString*) const override;
     int enclave() const override { return kAnyThread_Enclave; }
     const char* fileExtension() const override { return "xps"; }
+
+private:
+    bool fMultiPage;
 };
 
 class RasterSink : public Sink {