add mipmaps to scaledimagecache

src/core/SkMipMap.h

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkMipMap_DEFINED
 #define SkMipMap_DEFINED
 
 #include "SkRefCnt.h"
 #include "SkScalar.h"
 
 class SkBitmap;
 
 class SkMipMap : public SkRefCnt {
 public:
     static SkMipMap* Build(const SkBitmap& src);
 
     struct Level {
         void*       fPixels;
         uint32_t    fRowBytes;
         uint32_t    fWidth, fHeight;
+        float       fScale; // < 1.0
     };
 
     bool extractLevel(SkScalar scale, Level*) const;
 
+    size_t getSize() const { return fSize; }
+
 private:
+    size_t  fSize;
     Level*  fLevels;
     int     fCount;
 
     // we take ownership of levels, and will free it with sk_free()
-    SkMipMap(Level* levels, int count) : fLevels(levels), fCount(count) {
-        SkASSERT(levels);
-        SkASSERT(count > 0);
-    }
-
-    virtual ~SkMipMap() {
-        sk_free(fLevels);
-    }
+    SkMipMap(Level* levels, int count, size_t size);
+    virtual ~SkMipMap();
 
     static Level* AllocLevels(int levelCount, size_t pixelSize);
 };
 
 #endif