GM: create GmResultDigest that encapsulates digest type ("bitmap-64bitMD5") and value (12345)

tools/skimage_main.cpp

Index: tools/skimage_main.cpp
===================================================================
--- tools/skimage_main.cpp	(revision 9256)
+++ tools/skimage_main.cpp	(working copy)
@@ -180,7 +180,7 @@
 static Json::Value gExpectationsToWrite;
 
 /**
- *  If expectations are to be recorded, record the expected checksum of bitmap into global
+ *  If expectations are to be recorded, record the bitmap expectations into global
  *  expectations array.
  */
 static void write_expectations(const SkBitmap& bitmap, const char* filename) {
@@ -219,16 +219,8 @@
         return false;
     }
 
-    SkHashDigest checksum;
-    if (!SkBitmapHasher::ComputeDigest(bitmap, &checksum)) {
-        if (failureArray != NULL) {
-            failureArray->push_back().printf("decoded %s, but could not create a checksum.",
-                                             filename);
-        }
-        return false;
-    }
-
-    if (jsExpectation.match(checksum)) {
+    skiagm::GmResultDigest resultDigest(bitmap);
+    if (jsExpectation.match(resultDigest)) {
         return true;
     }