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

gm/tests/outputs/compared-against-different-pixels-images/output-expected/json-summary.txt

Index: gm/tests/outputs/compared-against-different-pixels-images/output-expected/json-summary.txt
===================================================================
--- gm/tests/outputs/compared-against-different-pixels-images/output-expected/json-summary.txt	(revision 9256)
+++ gm/tests/outputs/compared-against-different-pixels-images/output-expected/json-summary.txt	(working copy)
@@ -1,12 +1,8 @@
 {
    "actual-results" : {
       "failed" : {
-         "565/selftest1.png" : {
-            "bitmap-64bitMD5" : 12927999507540085554
-         },
-         "8888/selftest1.png" : {
-            "bitmap-64bitMD5" : 1209453360120438698
-         }
+         "565/selftest1.png" : [ "bitmap-64bitMD5", 12927999507540085554 ],
+         "8888/selftest1.png" : [ "bitmap-64bitMD5", 1209453360120438698 ]
       },
       "failure-ignored" : null,
       "no-comparison" : null,
@@ -14,11 +10,15 @@
    },
    "expected-results" : {
       "565/selftest1.png" : {
-         "allowed-bitmap-64bitMD5s" : [ 8863920166200910451 ],
+         "allowed-digests" : [
+            [ "bitmap-64bitMD5", 8863920166200910451 ]

[epoger, 2013/05/23 19:18:31]

Note the newly symmetrical actual and expectation formats.  For each possible
result, a type/value pair.

+         ],
          "ignore-failure" : false
       },
       "8888/selftest1.png" : {
-         "allowed-bitmap-64bitMD5s" : [ 13451349865803053525 ],
+         "allowed-digests" : [
+            [ "bitmap-64bitMD5", 13451349865803053525 ]
+         ],
          "ignore-failure" : false
       }
    }