Add a dedicated Result for skipped tests.

json_reporter.schema.json

 {
   "$schema": "http://json-schema.org/draft-04/schema#",
   "description": "An event emitted by the test package's JSON reporter",
 
   "definitions": {
     "GroupEntry": {
       "required": [
         "id",
         "suiteID",
         "metadata",
@@ skipping 147 matching lines @@
         "type": {"enum": ["error"]},
         "testID": {"type": "integer", "minimum": 0},
         "error": {"type": "string"},
         "stackTrace": {"type": "string"},
         "isFailure": {"type": "boolean"}
       }
     },
 
     {
       "title": "TestDoneEvent",
-      "required": ["testID", "result", "hidden"],
+      "required": ["testID", "result", "hidden", "skipped"],
       "properties": {
         "type": {"enum": ["testDone"]},
         "testID": {"type": "integer", "minimum": 0},
         "result": {"type": "string", "enum": ["success", "failure", "error"]},
-        "hidden": {"type": "boolean"}
+        "hidden": {"type": "boolean"},
+        "skipped": {"type": "boolean"}
       }
     },
 
     {
       "title": "DoneEvent",
       "required": ["success"],
       "properties": {
         "type": {"enum": ["done"]},
         "success": {"type": "boolean"}
       }
     },
 
     {
       "title": "FutureEvent",
       "description":
         "A placeholder event to allow new events to be added in the future.",
       "properties": {
         "type": {
           "not": {
             "enum": [
               "start", "testStart", "allSuites", "suite", "group", "print",
               "error", "testDone", "done"
             ]
           }
         }
       }
     }
   ]
 }