Change implementation of flush-count based GrGpuResource purging

src/gpu/GrGpuResourceCacheAccess.h

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrGpuResourceCacheAccess_DEFINED
 #define GrGpuResourceCacheAccess_DEFINED
 
@@ skipping 40 matching lines @@
 
     /** Called by the cache to assign a new unique key. */
     void setUniqueKey(const GrUniqueKey& key) { fResource->fUniqueKey = key; }
 
     /** Called by the cache to make the unique key invalid. */
     void removeUniqueKey() { fResource->fUniqueKey.reset(); }
 
     uint32_t timestamp() const { return fResource->fTimestamp; }
     void setTimestamp(uint32_t ts) { fResource->fTimestamp = ts; }
 
+    /** Called by the cache to record when this became purgeable. */
+    void setFlushCntWhenResourceBecamePurgeable(uint32_t cnt) {
+        SkASSERT(fResource->isPurgeable());
+        fResource->fExternalFlushCntWhenBecamePurgeable = cnt;
+    }
+    /**
+     * Called by the cache to determine whether this resource has been puregable for more than
+     * a threshold number of external flushes.
+     */
+    uint32_t flushCntWhenResourceBecamePurgeable() {
+        SkASSERT(fResource->isPurgeable());
+        return fResource->fExternalFlushCntWhenBecamePurgeable;
+    }
+
     int* accessCacheIndex() const { return &fResource->fCacheArrayIndex; }
 
     CacheAccess(GrGpuResource* resource) : fResource(resource) {}
     CacheAccess(const CacheAccess& that) : fResource(that.fResource) {}
     CacheAccess& operator=(const CacheAccess&); // unimpl
 
     // No taking addresses of this type.
     const CacheAccess* operator&() const;
     CacheAccess* operator&();
 
     GrGpuResource* fResource;
 
     friend class GrGpuResource; // to construct/copy this type.
     friend class GrResourceCache; // to use this type
     friend void test_unbudgeted_to_scratch(skiatest::Reporter* reporter); // for unit testing
 };
 
 inline GrGpuResource::CacheAccess GrGpuResource::cacheAccess() { return CacheAccess(this); }
 
 inline const GrGpuResource::CacheAccess GrGpuResource::cacheAccess() const {
     return CacheAccess(const_cast<GrGpuResource*>(this));
 }
 
 #endif