Implement PrintPageAsJPEG feature for Print Preview

src/chrome/renderer/print_web_view_helper.h

Index: src/chrome/renderer/print_web_view_helper.h
===================================================================
--- src/chrome/renderer/print_web_view_helper.h	(revision 25428)
+++ src/chrome/renderer/print_web_view_helper.h	(working copy)
@@ -75,6 +75,14 @@
   // Notification when printing is done - signal teardown
   void DidFinishPrinting(bool success);
 
+  // Prints the page listed in |params| as a JPEG image. The width and height of
+  // the image will scale propotionally given the |zoom_factor| multiplier. The
+  // encoded JPEG data will be written into the supplied vector |image_data|.
+  void PrintPageAsJPEG(const ViewMsg_PrintPage_Params& params,
+                       WebKit::WebFrame* frame,
+                       float zoom_factor,
+                       std::vector<unsigned char>* image_data);
+
  protected:
   bool CopyAndPrint(const ViewMsg_PrintPages_Params& params,
                     WebKit::WebFrame* web_frame);