Update callers of httputils.ReportError to specify message

ct/go/ctfe/chromium_builds/chromium_builds.go

 /*
         Handlers and types specific to Chromium builds.
 */
 
 package chromium_builds
 
 import (
         "bufio"
         "bytes"
         "database/sql"
@@ skipping 140 matching lines @@
 }
 
 func addTaskHandler(w http.ResponseWriter, r *http.Request) {
         task_common.AddTaskHandler(w, r, &AddTaskVars{})
 }
 
 func getRevDataHandler(getLkgr func() (string, error), gitRepoUrl string, w http.ResponseWriter, r *http.Request) {
         w.Header().Set("Content-Type", "application/json")
         revString := r.FormValue("rev")
         if revString == "" {
-                httputils.ReportError(w, r, fmt.Errorf("No revision specified"), "")
+                httputils.ReportError(w, r, nil, "No revision specified")
                 return
         }
 
         if strings.EqualFold(revString, "LKGR") {
                 lkgr, err := getLkgr()
                 if err != nil {
-                        httputils.ReportError(w, r, fmt.Errorf("Unable to retrieve LKGR revision"), "")
+                        httputils.ReportError(w, r, nil, "Unable to retrieve LKGR revision")
                 }
                 glog.Infof("Retrieved LKGR commit hash: %s", lkgr)
                 revString = lkgr
         }
         commitUrl := gitRepoUrl + revString + "?format=JSON"
         glog.Infof("Reading revision detail from %s", commitUrl)
         resp, err := httpClient.Get(commitUrl)
         if err != nil {
                 httputils.ReportError(w, r, err, "Unable to retrieve revision detail")
                 return
         }
         defer skutil.Close(resp.Body)
         if resp.StatusCode == 404 {
                 // Return successful empty response, since the user could be typing.
                 if err := json.NewEncoder(w).Encode(map[string]interface{}{}); err != nil {
                         httputils.ReportError(w, r, err, fmt.Sprintf("Failed to encode JSON: %v", err))
                         return
                 }
                 return
         }
         if resp.StatusCode != 200 {
-                httputils.ReportError(w, r, fmt.Errorf("Unable to retrieve revision detail"), "")
+                httputils.ReportError(w, r, nil, "Unable to retrieve revision detail")
                 return
         }
         // Remove junk in the first line. https://code.google.com/p/gitiles/issues/detail?id=31
         bufBody := bufio.NewReader(resp.Body)
         if _, err = bufBody.ReadString('\n'); err != nil {
                 httputils.ReportError(w, r, err, "Unable to retrieve revision detail")
                 return
         }
         if _, err = io.Copy(w, bufBody); err != nil {
                 httputils.ReportError(w, r, err, "Unable to retrieve revision detail")
@@ skipping 94 matching lines @@
         r.HandleFunc("/"+ctfeutil.CHROMIUM_BUILD_URI, addTaskView).Methods("GET")
         r.HandleFunc("/"+ctfeutil.CHROMIUM_BUILD_RUNS_URI, runsHistoryView).Methods("GET")
         r.HandleFunc("/"+ctfeutil.CHROMIUM_REV_DATA_POST_URI, getChromiumRevDataHandler).Methods("POST")
         r.HandleFunc("/"+ctfeutil.SKIA_REV_DATA_POST_URI, getSkiaRevDataHandler).Methods("POST")
         r.HandleFunc("/"+ctfeutil.ADD_CHROMIUM_BUILD_TASK_POST_URI, addTaskHandler).Methods("POST")
         r.HandleFunc("/"+ctfeutil.GET_CHROMIUM_BUILD_TASKS_POST_URI, getTasksHandler).Methods("POST")
         r.HandleFunc("/"+ctfeutil.UPDATE_CHROMIUM_BUILD_TASK_POST_URI, updateTaskHandler).Methods("POST")
         r.HandleFunc("/"+ctfeutil.DELETE_CHROMIUM_BUILD_TASK_POST_URI, deleteTaskHandler).Methods("POST")
         r.HandleFunc("/"+ctfeutil.REDO_CHROMIUM_BUILD_TASK_POST_URI, redoTaskHandler).Methods("POST")
 }