GM: run mode comparisons for all raster configs.

gm/tests/outputs/pipe-playback-failure/output-expected/json-summary.txt

 {
    "actual-results" : {
       "failed" : {
-         "comparison/selftest1-pipe.png" : [ "bitmap-64bitMD5", 6140979239232854774 ]
+         "565/selftest1-pipe.png" : [ "bitmap-64bitMD5", 6140979239232854774 ],
+         "8888/selftest1-pipe.png" : [ "bitmap-64bitMD5", 6140979239232854774 ]
       },
       "failure-ignored" : null,
       "no-comparison" : null,
       "succeeded" : {
          "565/selftest1.png" : [ "bitmap-64bitMD5", 12927999507540085554 ],
          "8888/selftest1.png" : [ "bitmap-64bitMD5", 1209453360120438698 ]
       }
    },
    "expected-results" : {
+      "565/selftest1-pipe.png" : {
+         "allowed-digests" : [
+            [ "bitmap-64bitMD5", 12927999507540085554 ]
+         ],
+         "ignore-failure" : false
+      },
       "565/selftest1.png" : {
          "allowed-digests" : [
             [ "bitmap-64bitMD5", 12927999507540085554 ]
          ],
          "ignore-failure" : false
       },
+      "8888/selftest1-pipe.png" : {
+         "allowed-digests" : [
+            [ "bitmap-64bitMD5", 1209453360120438698 ]
+         ],
+         "ignore-failure" : false
+      },
       "8888/selftest1.png" : {
          "allowed-digests" : [
             [ "bitmap-64bitMD5", 1209453360120438698 ]
          ],
-         "ignore-failure" : false
-      },
-      "comparison/selftest1-pipe.png" : {
-         "allowed-digests" : [
-            [ "bitmap-64bitMD5", 1209453360120438698 ]
-         ],
          "ignore-failure" : false
       }
    }
 }