Make GrResourceCache dynamically change between LRU and random replacement strategies.

include/gpu/GrGpuResource.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 GrGpuResource_DEFINED
 #define GrGpuResource_DEFINED
 
@@ skipping 40 matching lines @@
     // not intended to cross thread boundaries.
     void ref() const {
         this->validate();
         ++fRefCnt;
     }
 
     void unref() const {
         this->validate();
 
         if (!(--fRefCnt)) {
+            SkASSERT(fRefCnt >= 0);
             if (!static_cast<const DERIVED*>(this)->notifyRefCountIsZero()) {
                 return;
             }
         }
 
         this->didRemoveRefOrPendingIO(kRef_CntType);
     }
 
     void validate() const {
 #ifdef SK_DEBUG
@@ skipping 39 matching lines @@
     }
 
     void completedWrite() const {
         this->validate();
         --fPendingWrites;
         this->didRemoveRefOrPendingIO(kPendingWrite_CntType);
     }
 
 private:
     void didRemoveRefOrPendingIO(CntType cntTypeRemoved) const {
+        this->validate();
         if (0 == fPendingReads && 0 == fPendingWrites && 0 == fRefCnt) {
             static_cast<const DERIVED*>(this)->notifyAllCntsAreZero(cntTypeRemoved);
         }
     }
 
     mutable int32_t fRefCnt;
     mutable int32_t fPendingReads;
     mutable int32_t fPendingWrites;
 
     // This class is used to manage conversion of refs to pending reads/writes.
@@ skipping 170 matching lines @@
 
     SkBudgeted                  fBudgeted;
     bool                        fRefsWrappedObjects;
     const uint32_t              fUniqueID;
 
     typedef GrIORef<GrGpuResource> INHERITED;
     friend class GrIORef<GrGpuResource>; // to access notifyAllCntsAreZero and notifyRefCntIsZero.
 };
 
 #endif