Add a way to monitor cache hits and misses for deferred decoding.

src/lazy/SkLazyPixelRef.h

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkLazyPixelRef_DEFINED
 #define SkLazyPixelRef_DEFINED
 
 #include "SkBitmapFactory.h"
 #include "SkImage.h"
 #include "SkPixelRef.h"
 #include "SkFlattenable.h"
 
 class SkColorTable;
 class SkData;
 class SkImageCache;
 
+#ifdef SK_DEBUG
+    #define LAZY_CACHE_STATS 1
+#elif !defined(LAZY_CACHE_STATS)
+    #define LAZY_CACHE_STATS 0
+#endif
+
 /**
  *  PixelRef which defers decoding until SkBitmap::lockPixels() is called.
  */
 class SkLazyPixelRef : public SkPixelRef {
 
 public:
     /**
      *  Create a new SkLazyPixelRef.
      *  @param SkData Encoded data representing the pixels.
      *  @param DecodeProc Called to decode the pixels when needed. Must be non-NULL.
      *  @param SkImageCache Object that handles allocating and freeing the pixel memory, as needed.
      *         Must not be NULL.
      */
     SkLazyPixelRef(SkData*, SkBitmapFactory::DecodeProc, SkImageCache*);
 
     virtual ~SkLazyPixelRef();
 
 #ifdef SK_DEBUG
     intptr_t getCacheId() const { return fCacheId; }
 #endif
 
+#if LAZY_CACHE_STATS
+    static int32_t GetCacheHits() { return gCacheHits; }
+    static int32_t GetCacheMisses() { return gCacheMisses; }
+    static void ResetCacheStats() { gCacheHits = gCacheMisses = 0; }
+#endif
+
     // No need to flatten this object. When flattening an SkBitmap, SkOrderedWriteBuffer will check
     // the encoded data and write that instead.
     // Future implementations of SkFlattenableWriteBuffer will need to special case for
     // onRefEncodedData as well.
     SK_DECLARE_UNFLATTENABLE_OBJECT()
 
 protected:
     virtual void* onLockPixels(SkColorTable**) SK_OVERRIDE;
     virtual void onUnlockPixels() SK_OVERRIDE;
     virtual bool onLockPixelsAreWritable() const SK_OVERRIDE { return false; }
     virtual SkData* onRefEncodedData() SK_OVERRIDE;
 
 private:
     bool                        fErrorInDecoding;
     SkData*                     fData;
     SkBitmapFactory::DecodeProc fDecodeProc;
     SkImageCache*               fImageCache;
     intptr_t                    fCacheId;
 
+#if LAZY_CACHE_STATS
+    static int32_t              gCacheHits;
+    static int32_t              gCacheMisses;
+#endif
+
     typedef SkPixelRef INHERITED;
 };
 
 #endif  // SkLazyPixelRef_DEFINED