SkData to SkStreamAsset to avoid unneeded copying

dm/DMPDFRasterizeTask.h

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef DMPDFRasterizeTask_DEFINED
 #define DMPDFRasterizeTask_DEFINED
 
 #include "DMTask.h"
 #include "SkBitmap.h"
 #include "SkData.h"
 #include "SkStream.h"
 #include "SkString.h"
 #include "SkTemplates.h"
 
 namespace DM {
 
 typedef bool (*RasterizePdfProc)(SkStream* pdf, SkBitmap* output);
 
 class PDFRasterizeTask : public CpuTask {
 public:
+    // takes ownership of SkStreamAsset.
     PDFRasterizeTask(const Task& parent,
-                     SkData* pdf,
+                     SkStreamAsset* pdf,
                      RasterizePdfProc);
 
     virtual void draw() SK_OVERRIDE;
     virtual bool shouldSkip() const SK_OVERRIDE { return NULL == fRasterize; }
     virtual SkString name()   const SK_OVERRIDE { return fName; }
 
 private:
     const SkString fName;
-    SkAutoTUnref<SkData> fPdf;
+    SkAutoTDelete<SkStreamAsset> fPdf;
     RasterizePdfProc fRasterize;
 };
 
 }  // namespace DM
 
 #endif  // DMPDFRasterizeTask_DEFINED