Allow SkLazyPixelRef to use SkScaledImageCache

src/lazy/SkLazyPixelRef.h

Index: src/lazy/SkLazyPixelRef.h
diff --git a/src/lazy/SkLazyPixelRef.h b/src/lazy/SkLazyPixelRef.h
index 8f7a751e953693efd0b81cc9e0bafd24dba6154c..c7281d035aa19c4ce8783397931335b201fd73fa 100644
--- a/src/lazy/SkLazyPixelRef.h
+++ b/src/lazy/SkLazyPixelRef.h
@@ -33,8 +33,9 @@ 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.
+     *  @param SkImageCache Object that handles allocating and freeing
+     *         the pixel memory, as needed.  If NULL, use the global
+     *         SkScaledImageCache.
      */
     SkLazyPixelRef(SkData*, SkBitmapFactory::DecodeProc, SkImageCache*);
 
@@ -64,14 +65,25 @@ protected:
     virtual bool onImplementsDecodeInto() SK_OVERRIDE;
     virtual bool onDecodeInto(int pow2, SkBitmap*) SK_OVERRIDE;
 
+    /**
+     *  The allocator is used when (fImageCache==NULL) to allocate
+     *  concrete PixelRefs as needed.  If NULL, use the default allocator.
+     *  This is passed directly into SkBitmap::allocPixels().
+     */
+    virtual void setAllocator(SkBitmap::Allocator * allocator = NULL) {
+        fAllocator = allocator;

[scroggo, 2013/10/23 15:27:49]

SkBitmap::Allocator inherits from SkRefCnt. Typically we would take ownership
via

SkRefCnt_SafeAssign(fAllocator, allocator);

If for some reason we do not want to follow that pattern here, the comment
should explain that ownership of fAllocator is not transferred.

Is this meant to be protected? Are we going to have a subclass of SkLazyPixelRef
that calls it?

[hal.canary, 2013/10/23 16:11:52]

I'll make that change, unless there is any reason that the Allocator shouldn't
bother incrementing itself.
 
Good catch.  I would have (hopefully) caught this after I wrote my unit tests.

+    }
+
 private:
     bool                        fErrorInDecoding;
     SkData*                     fData;
     SkBitmapFactory::DecodeProc fDecodeProc;
     SkImageCache*               fImageCache;
+    // fCacheId is a (SkScaledImageCache::ID*) or a (SkImageCache::ID).
     intptr_t                    fCacheId;
     size_t                      fRowBytes;
     SkImage::Info               fLazilyCachedInfo;
+    SkBitmap::Allocator*        fAllocator;
 
 #if LAZY_CACHE_STATS
     static int32_t              gCacheHits;