More work to integrate skimage with rebaseline tools.

gm/gm_expectations.h

Index: gm/gm_expectations.h
diff --git a/gm/gm_expectations.h b/gm/gm_expectations.h
index 401af0dab5aefa28fb9ed4760eb48c65909b99dc..5ff009e1677e30bb782a00ff4b486427920171e9 100644
--- a/gm/gm_expectations.h
+++ b/gm/gm_expectations.h
@@ -116,7 +116,12 @@ namespace skiagm {
          * Expect exactly one image (appropriate for the case when we
          * are comparing against a single PNG file).
          */
-        Expectations(const SkBitmap& bitmap, bool ignoreFailure=kDefaultIgnoreFailure);
+        explicit Expectations(const SkBitmap& bitmap, bool ignoreFailure=kDefaultIgnoreFailure);
+
+        /**
+         * Expect exactly one image, whose digest has already been computed.
+         */
+        explicit Expectations(const BitmapAndDigest& bitmapAndDigest);
 
         /**
          * Create Expectations from a JSON element as found within the