Use SkTransferFunctionBehavior in SkImageGenerator

This fixes SkColorSpaceXformCanvas gms that expect
non-linear premuls from the codec.

BUG=skia:

Change-Id: I5dc236d0cd760c23605a26e9c33ddb18955f9231
Reviewed-on: https://skia-review.googlesource.com/10164
Reviewed-by: Mike Klein <mtklein@chromium.org>
Commit-Queue: Matt Sarett <msarett@google.com>
diff --git a/src/codec/SkCodecImageGenerator.h b/src/codec/SkCodecImageGenerator.h
index 727a747..a435205 100644
--- a/src/codec/SkCodecImageGenerator.h
+++ b/src/codec/SkCodecImageGenerator.h
@@ -24,7 +24,9 @@
     SkData* onRefEncodedData(GrContext* ctx) override;
 
     bool onGetPixels(const SkImageInfo& info, void* pixels, size_t rowBytes, SkPMColor ctable[],
-            int* ctableCount) override;
+                     int* ctableCount) override;
+    bool onGetPixels(const SkImageInfo& info, void* pixels, size_t rowBytes, const Options& opts)
+                     override;
 
     bool onQueryYUV8(SkYUVSizeInfo*, SkYUVColorSpace*) const override;