Implement SkImageFilter::Cache with SkResourceCache.

include/core/SkImageFilter.h

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkImageFilter_DEFINED
 #define SkImageFilter_DEFINED
 
@@ skipping 24 matching lines @@
     // This cache maps from (filter's unique ID + CTM + clipBounds + src bitmap generation ID) to
     // (result, offset).
     class Cache : public SkRefCnt {
     public:
         struct Key;
         virtual ~Cache() {}
         static Cache* Create(size_t maxBytes);
         static Cache* Get();
         virtual bool get(const Key& key, SkBitmap* result, SkIPoint* offset) const = 0;
         virtual void set(const Key& key, const SkBitmap& result, const SkIPoint& offset) = 0;
-        virtual void purge() {}
     };
 
     class Context {
     public:
         Context(const SkMatrix& ctm, const SkIRect& clipBounds, Cache* cache) :
             fCTM(ctm), fClipBounds(clipBounds), fCache(cache) {
         }
         const SkMatrix& ctm() const { return fCTM; }
         const SkIRect& clipBounds() const { return fClipBounds; }
         Cache* cache() const { return fCache; }
@@ skipping 312 matching lines @@
 
     /**
      * Returns true if this filter can cause transparent black pixels to become
      * visible (ie., alpha > 0). The default implementation returns false. This
      * function is non-recursive, i.e., only queries this filter and not its
      * inputs.
      */
     virtual bool affectsTransparentBlack() const;
 
 private:
-    friend class SkGraphics;
-    static void PurgeCache();
-
     bool usesSrcInput() const { return fUsesSrcInput; }
 
     typedef SkFlattenable INHERITED;
     int fInputCount;
     SkImageFilter** fInputs;
     bool fUsesSrcInput;
     CropRect fCropRect;
     uint32_t fUniqueID; // Globally unique
 };
 
 /**
  *  Helper to unflatten the common data, and return NULL if we fail.
  */
 #define SK_IMAGEFILTER_UNFLATTEN_COMMON(localVar, expectedCount)    \
     Common localVar;                                                \
     do {                                                            \
         if (!localVar.unflatten(buffer, expectedCount)) {           \
             return NULL;                                            \
         }                                                           \
     } while (0)
 
 #endif