cache SkImage::Info calculation in lazypixelref

src/lazy/SkLazyPixelRef.h

Index: src/lazy/SkLazyPixelRef.h
diff --git a/src/lazy/SkLazyPixelRef.h b/src/lazy/SkLazyPixelRef.h
index c51675dd5f301e648e20db0daa40db3a1d7faae6..8f7a751e953693efd0b81cc9e0bafd24dba6154c 100644
--- a/src/lazy/SkLazyPixelRef.h
+++ b/src/lazy/SkLazyPixelRef.h
@@ -71,12 +71,16 @@ private:
     SkImageCache*               fImageCache;
     intptr_t                    fCacheId;
     size_t                      fRowBytes;
+    SkImage::Info               fLazilyCachedInfo;
 
 #if LAZY_CACHE_STATS
     static int32_t              gCacheHits;
     static int32_t              gCacheMisses;
 #endif
 
+    // lazily initialized our cached info. Returns NULL on failure.
+    const SkImage::Info* getCachedInfo();
+
     typedef SkPixelRef INHERITED;
 };