return and take SkImageGenerator as unique_ptr

BUG=skia:

Change-Id: I4bc11042dd1dbf1eabd40af206027bc65acc3186
Reviewed-on: https://skia-review.googlesource.com/8444
Commit-Queue: Mike Reed <reed@google.com>
Reviewed-by: Matt Sarett <msarett@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
diff --git a/dm/DMSrcSink.cpp b/dm/DMSrcSink.cpp
index 3b849c1..d28c3a2 100644
--- a/dm/DMSrcSink.cpp
+++ b/dm/DMSrcSink.cpp
@@ -907,7 +907,7 @@
     std::unique_ptr<SkImageGenerator> gen(nullptr);
     switch (fMode) {
         case kCodec_Mode:
-            gen.reset(SkCodecImageGenerator::NewFromEncodedCodec(encoded.get()));
+            gen = SkCodecImageGenerator::MakeFromEncodedCodec(encoded);
             if (!gen) {
                 return "Could not create codec image generator.";
             }
@@ -931,7 +931,7 @@
 
     // Test deferred decoding path on GPU
     if (fIsGpu) {
-        sk_sp<SkImage> image(SkImage::MakeFromGenerator(gen.release(), nullptr));
+        sk_sp<SkImage> image(SkImage::MakeFromGenerator(std::move(gen), nullptr));
         if (!image) {
             return "Could not create image from codec image generator.";
         }