Reland of Improve linearized pdf load/show time.

pdf/pdf_engine.h

Index: pdf/pdf_engine.h
diff --git a/pdf/pdf_engine.h b/pdf/pdf_engine.h
index a394d0271f2d94af72b01fd70c48e7e49150425f..334e2cc5ed54674c69e9d7dd5e9b20c9c68e34a4 100644
--- a/pdf/pdf_engine.h
+++ b/pdf/pdf_engine.h
@@ -186,6 +186,9 @@ class PDFEngine {
     // Get the background color of the PDF.
     virtual uint32_t GetBackgroundColor() = 0;
 
+    // Cancel browser initiated document download.
+    virtual void CancelBrowserDownload() = 0;
+
     // Sets selection status.
     virtual void IsSelectingChanged(bool is_selecting) {}
   };
@@ -298,8 +301,6 @@ class PDFEngine {
   virtual void SetScrollPosition(const pp::Point& position) = 0;
 #endif
 
-  virtual bool IsProgressiveLoad() = 0;
-
   virtual std::string GetMetadata(const std::string& key) = 0;
 };