hide Config in SkImageDecoder -- use SkColorType instead

patch from issue 334613003

TBR=scroggo

Author: reed@chromium.org

Review URL: https://codereview.chromium.org/334793002
diff --git a/tools/render_pictures_main.cpp b/tools/render_pictures_main.cpp
index ec21cb7..850053c 100644
--- a/tools/render_pictures_main.cpp
+++ b/tools/render_pictures_main.cpp
@@ -130,7 +130,7 @@
         SkDebugf("Failed to write encoded data to \"%s\"\n", outPath.c_str());
     }
     // Put in a dummy bitmap.
-    return SkImageDecoder::DecodeStream(&memStream, bitmap, SkBitmap::kNo_Config,
+    return SkImageDecoder::DecodeStream(&memStream, bitmap, kUnknown_SkColorType,
                                         SkImageDecoder::kDecodeBounds_Mode);
 }