add runtime option to provide data->imagegenerator factory

src/ports/SkImageGenerator_skia.cpp

Index: src/ports/SkImageGenerator_skia.cpp
diff --git a/src/ports/SkImageGenerator_skia.cpp b/src/ports/SkImageGenerator_skia.cpp
index f972253306d41c23d124613746eec7d243b91d2c..1dbc9a5f33e491cecc3fbde18f7e60e1e8331194 100644
--- a/src/ports/SkImageGenerator_skia.cpp
+++ b/src/ports/SkImageGenerator_skia.cpp
@@ -108,11 +108,7 @@ private:
     typedef SkImageGenerator INHERITED;
 };
 
-SkImageGenerator* SkImageGenerator::NewFromData(SkData* data) {
-    if (NULL == data) {
-        return NULL;
-    }
-
+SkImageGenerator* SkImageGenerator::NewFromEncodedImpl(SkData* data) {
     SkMemoryStream stream(data->data(), data->size(), false);
     SkImageDecoder* decoder = SkImageDecoder::Factory(&stream);
     if (NULL == decoder) {