Make AndroidOptions const

Make the struct passed to SkAndroidCodec::getAndroidPixels const. This
matches SkCodec, and makes sense, since it is not used as an output.

Brought up in crrev.com/1417583009

Review URL: https://codereview.chromium.org/1411693005
diff --git a/src/codec/SkSampledCodec.h b/src/codec/SkSampledCodec.h
index bbd7d35..b3a5912 100644
--- a/src/codec/SkSampledCodec.h
+++ b/src/codec/SkSampledCodec.h
@@ -30,7 +30,7 @@
     bool onGetSupportedSubset(SkIRect* desiredSubset) const override { return true; }
 
     SkCodec::Result onGetAndroidPixels(const SkImageInfo& info, void* pixels, size_t rowBytes,
-            AndroidOptions& options) override;
+            const AndroidOptions& options) override;
 
 private:
     /**
@@ -55,7 +55,7 @@
      *  provide the scale by sampling.
      */
     SkCodec::Result sampledDecode(const SkImageInfo& info, void* pixels, size_t rowBytes,
-            AndroidOptions& options);
+            const AndroidOptions& options);
 
     SkAutoTDelete<SkCodec> fCodec;