unify peekPixels around pixmap parameter

src/image/SkImage_Generator.cpp

Index: src/image/SkImage_Generator.cpp
diff --git a/src/image/SkImage_Generator.cpp b/src/image/SkImage_Generator.cpp
index 688b4ffe3ba393c2f5871d605ac1263768ea8610..95cc426a43225d8819a107ddf50ae40bbabb0bb1 100644
--- a/src/image/SkImage_Generator.cpp
+++ b/src/image/SkImage_Generator.cpp
@@ -22,7 +22,6 @@ public:
     {}
 
     bool onReadPixels(const SkImageInfo&, void*, size_t, int srcX, int srcY, CachingHint) const override;
-    const void* onPeekPixels(SkImageInfo*, size_t* /*rowBytes*/) const override;
     SkImageCacherator* peekCacherator() const override { return fCache; }
     SkData* onRefEncoded(GrContext*) const override;
     bool isOpaque() const override { return fCache->info().isOpaque(); }
@@ -62,10 +61,6 @@ bool SkImage_Generator::onReadPixels(const SkImageInfo& dstInfo, void* dstPixels
     return false;
 }
 
-const void* SkImage_Generator::onPeekPixels(SkImageInfo* infoPtr, size_t* rowBytesPtr) const {
-    return NULL;
-}
-
 SkData* SkImage_Generator::onRefEncoded(GrContext* ctx) const {
     return fCache->refEncoded(ctx);
 }