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..fac038c8aad35b8da569ed222674bf2f1c73bfd5 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 +20,27 @@ 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;
+  // Starts conversion of PDF provided as |data|. Calls |start_callback|
+  // with positive |page_count|. |page_count| is 0 if initialization failed.
+  virtual void Start(const scoped_refptr<base::RefCountedMemory>& data,
+                     const PdfRenderSettings& conversion_settings,
+                     const StartCallback& start_callback) = 0;
+
+  // Requests conversion of the page. |page_number| is 0-base page number in
+  // PDF provided in Start() call.
+  // Calls |get_page_callback| after conversion. |emf| of callback in not NULL
+  // if conversion succeeded.
+  virtual void GetPage(int page_number,
+                       const GetPageCallback& get_page_callback) = 0;
 };
 
 }  // namespace printing