take gr-context parameter to refEncoded, indicating a desire for only gpu-specific formats

src/images/SkDecodingImageGenerator.cpp

Index: src/images/SkDecodingImageGenerator.cpp
diff --git a/src/images/SkDecodingImageGenerator.cpp b/src/images/SkDecodingImageGenerator.cpp
index 8cfacc3fba10a876eea00cb89d79a2cb8126a00a..8d55bd36c7b07c2aa6cb40bb925f63f1a4af8a1e 100644
--- a/src/images/SkDecodingImageGenerator.cpp
+++ b/src/images/SkDecodingImageGenerator.cpp
@@ -37,7 +37,7 @@ public:
                            bool ditherImage);
 
 protected:
-    SkData* onRefEncodedData() override;
+    SkData* onRefEncodedData(SK_REFENCODEDDATA_CTXPARAM) override;
     bool onGetPixels(const SkImageInfo& info, void* pixels, size_t rowBytes,
                      SkPMColor ctable[], int* ctableCount) override;
     bool onGetYUV8Planes(SkISize sizes[3], void* planes[3], size_t rowBytes[3],
@@ -126,7 +126,7 @@ DecodingImageGenerator::~DecodingImageGenerator() {
     SkSafeUnref(fData);
 }
 
-SkData* DecodingImageGenerator::onRefEncodedData() {
+SkData* DecodingImageGenerator::onRefEncodedData(SK_REFENCODEDDATA_CTXPARAM) {
     // This functionality is used in `gm --serialize`
     // Does not encode options.
     if (nullptr == fData) {