use SkBitmapProvider for shader-context

src/core/SkBitmapController.h

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkBitmapController_DEFINED
 #define SkBitmapController_DEFINED
 
 #include "SkBitmap.h"
 #include "SkBitmapCache.h"
 #include "SkFilterQuality.h"
 #include "SkImage.h"
 #include "SkMatrix.h"
 
 class SkBitmapProvider {
 public:
-    SkBitmapProvider(const SkBitmap& bm) : fBitmap(bm) {}
-    SkBitmapProvider(const SkImage* img) : fImage(SkRef(img)) {}
+    explicit SkBitmapProvider(const SkBitmap& bm) : fBitmap(bm) {}
+    explicit SkBitmapProvider(const SkImage* img) : fImage(SkSafeRef(img)) {}
+    SkBitmapProvider(const SkBitmapProvider& other)
+        : fBitmap(other.fBitmap)
+        , fImage(SkSafeRef(other.fImage.get()))
+    {}
 
     int width() const;
     int height() const;
     uint32_t getID() const;
 
     bool validForDrawing() const;
     SkImageInfo info() const;
 
     SkBitmapCacheDesc makeCacheDesc(int w, int h) const;
     SkBitmapCacheDesc makeCacheDesc() const;
@@ skipping 49 matching lines @@
 class SkDefaultBitmapController : public SkBitmapController {
 public:
     SkDefaultBitmapController() {}
     
 protected:
     State* onRequestBitmap(const SkBitmapProvider&, const SkMatrix& inverse, SkFilterQuality,
                            void* storage, size_t storageSize) override;
 };
 
 #endif