Enable generating SkImage with the same uniqueID in SkImageGenerator subclass

src/core/SkImageGenerator.cpp

Index: src/core/SkImageGenerator.cpp
diff --git a/src/core/SkImageGenerator.cpp b/src/core/SkImageGenerator.cpp
index c8c94c22707fe1dc5a57a8f54da7de24729665bf..84d9c743eb4daaab1238c4101b49429b31acdd93 100644
--- a/src/core/SkImageGenerator.cpp
+++ b/src/core/SkImageGenerator.cpp
@@ -8,9 +8,9 @@
 #include "SkImageGenerator.h"
 #include "SkNextID.h"
 
-SkImageGenerator::SkImageGenerator(const SkImageInfo& info)
+SkImageGenerator::SkImageGenerator(const SkImageInfo& info, uint32_t uniqueID)
     : fInfo(info)
-    , fUniqueID(SkNextID::ImageID())
+    , fUniqueID(kNeedNewImageUniqueID == uniqueID ? SkNextID::ImageID() : uniqueID)
 {}
 
 bool SkImageGenerator::getPixels(const SkImageInfo& info, void* pixels, size_t rowBytes,