Add isEncoded to SkImageGenerator

src/core/SkImageGenerator.cpp

Index: src/core/SkImageGenerator.cpp
diff --git a/src/core/SkImageGenerator.cpp b/src/core/SkImageGenerator.cpp
index 84d9c743eb4daaab1238c4101b49429b31acdd93..8221ac92b6b77252e5fd74e6b468394a1305fc31 100644
--- a/src/core/SkImageGenerator.cpp
+++ b/src/core/SkImageGenerator.cpp
@@ -109,6 +109,10 @@ bool SkImageGenerator::generateScaledPixels(const SkISize& scaledSize,
 
 /////////////////////////////////////////////////////////////////////////////////////////////
 
+bool SkImageGenerator::onIsEncoded() const {
+    return false;
+}
+
 SkData* SkImageGenerator::onRefEncodedData(SK_REFENCODEDDATA_CTXPARAM) {
     return nullptr;
 }