move SkBitmapProvider to its own file

src/core/SkBitmapProvider.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 SkBitmapProvider_DEFINED
+#define SkBitmapProvider_DEFINED
+
+#include "SkBitmap.h"
+#include "SkImage.h"
+#include "SkBitmapCache.h"
+
+class SkBitmapProvider {
+public:
+    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;
+    void notifyAddedToCache() const;
+
+    // Only call this if you're sure you need the bits, since it maybe expensive
+    // ... cause a decode and cache, or gpu-readback
+    bool asBitmap(SkBitmap*) const;
+
+private:
+    SkBitmap fBitmap;
+    SkAutoTUnref<const SkImage> fImage;
+};
+
+#endif