Add new tests to presubmit, fix errors

perf/go/trybot/trybot.go

 /** trybot is for loading and serving trybot performance results.
 
   Implementation notes:
 
     Regular files are in:
 
     gs://chromium-skia-gm/nano-json-v1/2014/08/07/01/Perf-...-Release/nanobench_da7a94...8d35a_1407357280.json
 
     while trybots are in:
 
@@ skipping 191 matching lines @@
         for _, b := range benchFilesByIssue {
                 if b.IssueName != lastIssue {
                         // Write out the current TryBotResults to the datastore and create a fresh new TryBotResults.
                         if cur != nil {
                                 if err := Write(lastIssue, cur); err != nil {
                                         return fmt.Errorf("Update failed to write trybot results: %s", err)
                                 }
                         }
                         if cur, err = Get(b.IssueName); err != nil {
                                 return fmt.Errorf("Failed to load existing trybot data for issue %s: %s", b.IssueName, err)
-                                continue
                         }
                         lastIssue = b.IssueName
                         glog.Infof("Switched to issue: %s", lastIssue)
                 }
                 addTryData(cur, b.ResultsFileLocation, counter)
         }
         if cur != nil {
                 if err := Write(lastIssue, cur); err != nil {
                         return fmt.Errorf("Update failed to write trybot results: %s", err)
                 }
         }
 
         glog.Infof("Finished trybot ingestion.")
 
         return nil
 }