SkImage doesn't use props, so don't need to store it

src/image/SkImage_Generator.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkImage_Base.h"
 #include "SkBitmap.h"
 #include "SkCanvas.h"
 #include "SkData.h"
 #include "SkImageCacherator.h"
 #include "SkImagePriv.h"
 #include "SkPixelRef.h"
 #include "SkSurface.h"
 
 class SkImage_Generator : public SkImage_Base {
 public:
     SkImage_Generator(SkImageCacherator* cache)
-        : INHERITED(cache->info().width(), cache->info().height(), cache->uniqueID(), NULL)
+        : INHERITED(cache->info().width(), cache->info().height(), cache->uniqueID())
         , fCache(cache) // take ownership
     {}
 
     bool onReadPixels(const SkImageInfo&, void*, size_t, int srcX, int srcY) const override;
     const void* onPeekPixels(SkImageInfo*, size_t* /*rowBytes*/) const override;
     SkData* onRefEncoded() const override;
     bool isOpaque() const override { return fCache->info().isOpaque(); }
     SkImage* onNewSubset(const SkIRect&) const override;
     bool getROPixels(SkBitmap*) const override;
     GrTexture* asTextureRef(GrContext*, SkImageUsageType) const override;
@@ skipping 48 matching lines @@
     return surface->newImageSnapshot();
 }
 
 SkImage* SkImage::NewFromGenerator(SkImageGenerator* generator, const SkIRect* subset) {
     SkImageCacherator* cache = SkImageCacherator::NewFromGenerator(generator, subset);
     if (!cache) {
         return nullptr;
     }
     return new SkImage_Generator(cache);
 }