call derived ~ from GrIORef

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 85 matching lines @@
     void completedWrite() const {
         this->validate();
         --fPendingWrites;
         this->didUnref();
     }
 
 private:
     void didUnref() const {
         if (0 == fPendingReads && 0 == fPendingWrites) {
             if (0 == fRefCnt) {
-                SkDELETE(this);
+                // Must call derived destructor since this is not a virtual class.
+                SkDELETE(static_cast<const DERIVED*>(this));
             } else if (1 == fRefCnt) {
                 // The one ref is the cache's
                 static_cast<const DERIVED*>(this)->notifyIsPurgable();
             }
         }
     }
 
     mutable int32_t fRefCnt;
     mutable int32_t fPendingReads;
     mutable int32_t fPendingWrites;
@@ skipping 142 matching lines @@
     GrResourceCacheEntry*   fCacheEntry;  // NULL if not in cache
     const uint32_t          fUniqueID;
 
     GrResourceKey           fScratchKey;
 
     typedef GrIORef<GrGpuResource> INHERITED;
     friend class GrIORef<GrGpuResource>; // to access notifyIsPurgable.
 };
 
 #endif