use colortype instead of config

patch from issue 172063004

BUG=skia:
R=scroggo@google.com

Review URL: https://codereview.chromium.org/173893002

git-svn-id: http://skia.googlecode.com/svn/trunk@13520 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/utils/SkPictureUtils.cpp b/src/utils/SkPictureUtils.cpp
index a7ec7ae..cda6405 100644
--- a/src/utils/SkPictureUtils.cpp
+++ b/src/utils/SkPictureUtils.cpp
@@ -54,7 +54,7 @@
 
     GatherPixelRefDevice(int width, int height, PixelRefSet* prset) {
         fSize.set(width, height);
-        fEmptyBitmap.setConfig(SkBitmap::kNo_Config, width, height);
+        fEmptyBitmap.setConfig(SkImageInfo::MakeUnknown(width, height));
         fPRSet = prset;
     }