add schema version to rebaseline_server intermediate JSON

gm/rebaseline_server/testdata/outputs/expected/results_test.ResultsTest.test_gm/gm.json

 {
   "extraColumnHeaders": {
     "builder": {
       "headerText": "builder", 
       "isFilterable": true, 
       "isSortable": true, 
       "valuesAndCounts": {
         "Test-Android-GalaxyNexus-SGX540-Arm7-Release": 13, 
         "Test-Mac10.7-MacMini4.1-GeForce320M-x86_64-Debug": 15
       }
@@ skipping 30 matching lines @@
         "aaclip": 2, 
         "bigblurs": 7, 
         "bitmapsource": 2, 
         "displacement": 5, 
         "filterbitmap_checkerboard_192_192": 2, 
         "filterbitmap_checkerboard_32_2": 2, 
         "texdata": 1
       }
     }
   }, 
+  "header": {
+    "dataHash": "2099241024256114776", 
+    "isEditable": false, 
+    "isExported": true, 
+    "schemaVersion": 1, 
+    "timeNextUpdateAvailable": null, 
+    "timeUpdated": 12345678, 
+    "type": "all"
+  }, 
   "imagePairs": [
     {
       "differenceData": {
         "maxDiffPerChannel": [
           128, 
           128, 
           128
         ], 
         "numDifferingPixels": 120000, 
         "percentDifferingPixels": 75.0, 
@@ skipping 475 matching lines @@
     {
       "baseUrl": "http://chromium-skia-gm.commondatastorage.googleapis.com/gm", 
       "description": "expected image"
     }, 
     {
       "baseUrl": "http://chromium-skia-gm.commondatastorage.googleapis.com/gm", 
       "description": "actual image"
     }
   ]
 }