Create a hash table from id<-->key in SkImageFilter::CacheImpl

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 @@
     // (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() {}
+        virtual void purgeByImageFilterId(uint32_t) {}
     };
 
     enum SizeConstraint {
         kExact_SizeConstraint,
         kApprox_SizeConstraint,
     };
 
     class Context {
     public:
         Context(const SkMatrix& ctm, const SkIRect& clipBounds, Cache* cache,
@@ skipping 396 matching lines @@
  */
 #define SK_IMAGEFILTER_UNFLATTEN_COMMON(localVar, expectedCount)    \
     Common localVar;                                                \
     do {                                                            \
         if (!localVar.unflatten(buffer, expectedCount)) {           \
             return NULL;                                            \
         }                                                           \
     } while (0)
 
 #endif