PDF: Put back removed SetScrollPosition().

pdf/pdf_engine.h

Index: pdf/pdf_engine.h
diff --git a/pdf/pdf_engine.h b/pdf/pdf_engine.h
index 5e1e2647b3a387399a563dcae4e76a1118446048..673a27c420ce0c2cb58c245d80c4fe87a62ea646 100644
--- a/pdf/pdf_engine.h
+++ b/pdf/pdf_engine.h
@@ -282,6 +282,13 @@ class PDFEngine {
   // document at page |index|.
   virtual void AppendPage(PDFEngine* engine, int index) = 0;
 
+#if defined(PDF_USE_XFA)
+  // Allow client to set scroll positions in document coordinates. Note that
+  // this is meant for cases where the device scale factor changes, and not for
+  // general scrolling - the engine will not repaint due to this.
+  virtual void SetScrollPosition(const pp::Point& position) = 0;
+#endif
+
   virtual bool IsProgressiveLoad() = 0;
 
   virtual std::string GetMetadata(const std::string& key) = 0;