Fix two leaks & improve leak tracking

include/lazy/SkPurgeableImageCache.h

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkPurgeableImageCache_DEFINED
 #define SkPurgeableImageCache_DEFINED
 
 #include "SkImageCache.h"
 
 #ifdef SK_DEBUG
     #include "SkTDArray.h"
 #endif
 
 /**
  *  Implementation for SkImageCache that uses system defined purgeable memory.
  */
 class SkPurgeableImageCache : public SkImageCache {
 
 public:
+    SK_DECLARE_INST_COUNT(SkPurgeableImageCache)
+
     static SkImageCache* Create();
 
     virtual void* allocAndPinCache(size_t bytes, ID*) SK_OVERRIDE;
     virtual void* pinCache(ID, SkImageCache::DataStatus*) SK_OVERRIDE;
     virtual void releaseCache(ID) SK_OVERRIDE;
     virtual void throwAwayCache(ID) SK_OVERRIDE;
 
 #ifdef SK_DEBUG
     virtual MemoryStatus getMemoryStatus(ID) const SK_OVERRIDE;
     virtual void purgeAllUnpinnedCaches() SK_OVERRIDE;
     virtual ~SkPurgeableImageCache();
 #endif
 
 private:
     SkPurgeableImageCache();
 
 #ifdef SK_DEBUG
     SkTDArray<ID> fRecs;
     int findRec(ID) const;
 #endif
     void removeRec(ID);
 };
 #endif // SkPurgeableImageCache_DEFINED