Use file handles to interact with utility process.

chrome/browser/printing/pdf_to_emf_converter.h

Index: chrome/browser/printing/pdf_to_emf_converter.h
diff --git a/chrome/browser/printing/pdf_to_emf_converter.h b/chrome/browser/printing/pdf_to_emf_converter.h
index ca7adc41bedfbdfb3501d0624f363873a920d9e0..902618ebfddbe4d072ac0f19fbbf4fa22067e4e9 100644
--- a/chrome/browser/printing/pdf_to_emf_converter.h
+++ b/chrome/browser/printing/pdf_to_emf_converter.h
@@ -7,7 +7,7 @@
 
 #include "base/callback.h"
 #include "base/memory/ref_counted_memory.h"
-#include "base/memory/scoped_vector.h"
+#include "base/memory/scoped_ptr.h"
 
 namespace base {
 class FilePath;
@@ -20,18 +20,21 @@ class PdfRenderSettings;
 
 class PdfToEmfConverter {
  public:
-  // Callback for when the PDF is converted to an EMF.
-  // Takes ownership of metafiles.
-  typedef base::Callback<void(double /*scale_factor*/,
-                              ScopedVector<MetafilePlayer>* /*emf_files*/)>
-      ResultCallback;
-  virtual ~PdfToEmfConverter() {}
+  typedef base::Callback<void(int page_count)> StartCallback;
+  typedef base::Callback<void(int page_number,
+                              double scale_factor,
+                              scoped_ptr<MetafilePlayer> emf)> GetPageCallback;
+
+  virtual ~PdfToEmfConverter();
 
   static scoped_ptr<PdfToEmfConverter> CreateDefault();
 
-  virtual void Start(base::RefCountedMemory* data,
-                     const printing::PdfRenderSettings& conversion_settings,
-                     const ResultCallback& callback) = 0;
+  virtual void Start(const scoped_refptr<base::RefCountedMemory>& data,

[Lei Zhang, 2014/09/16 03:36:54]

nit: document the abstract methods.

[Vitaly Buka (NO REVIEWS), 2014/09/16 07:50:36]

Done.

+                     const PdfRenderSettings& conversion_settings,
+                     const StartCallback& start_callback) = 0;
+
+  virtual void GetPage(int page_number,
+                       const GetPageCallback& get_page_callback) = 0;
 };
 
 }  // namespace printing