Add a SkPixelSerializer SkImage encode variant

src/image/SkImage.cpp

Index: src/image/SkImage.cpp
diff --git a/src/image/SkImage.cpp b/src/image/SkImage.cpp
index c55d28a177f16c5e075b3aa77113a959ee15cd56..5a67c84caf663cc16cc41f62ccff98cce68201fb 100644
--- a/src/image/SkImage.cpp
+++ b/src/image/SkImage.cpp
@@ -13,6 +13,7 @@
 #include "SkImage_Base.h"
 #include "SkNextID.h"
 #include "SkPixelRef.h"
+#include "SkPixelSerializer.h"
 #include "SkReadPixelsRec.h"
 #include "SkString.h"
 #include "SkSurface.h"
@@ -71,6 +72,40 @@ SkData* SkImage::encode(SkImageEncoder::Type type, int quality) const {
     return nullptr;
 }
 
+namespace {
+
+class DefaultSerializer :  public SkPixelSerializer {
+protected:
+    bool onUseEncodedData(const void *data, size_t len) override {
+        return true;
+    }
+
+    SkData* onEncodePixels(const SkImageInfo& info, const void* pixels, size_t rowBytes) override {
+        return SkImageEncoder::EncodeData(info, pixels, rowBytes, SkImageEncoder::kPNG_Type, 100);
+    }
+};
+
+} // anonymous namespace
+
+SkData* SkImage::encode(SkPixelSerializer* serializer) const {
+    DefaultSerializer defaultSerializer;
+    SkPixelSerializer* effectiveSerializer = serializer ? serializer : &defaultSerializer;
+
+    SkAutoTUnref<SkData> encoded(this->refEncoded());
+    if (encoded && effectiveSerializer->useEncodedData(encoded->data(), encoded->size())) {
+        return encoded.detach();
+    }
+
+    SkBitmap bm;
+    SkAutoPixmapUnlock apu;
+    if (as_IB(this)->getROPixels(&bm) && bm.requestLock(&apu)) {
+        const SkPixmap& pmap = apu.pixmap();
+        return effectiveSerializer->encodePixels(pmap.info(), pmap.addr(), pmap.rowBytes());
+    }
+
+    return nullptr;
+}
+
 SkData* SkImage::refEncoded() const {
     return as_IB(this)->onRefEncoded();
 }