Reset chromium checkout before syncing

ct/go/worker_scripts/capture_archives/main.go

 // Application that captures webpage archives on a CT worker and uploads it to
 // Google Storage.
 package main
 
 import (
         "flag"
         "fmt"
         "io/ioutil"
         "path/filepath"
 
@@ skipping 20 matching lines @@
 
         // Create the task file so that the master knows this worker is still busy.
         skutil.LogErr(util.CreateTaskFile(util.ACTIVITY_CAPTURING_ARCHIVES))
         defer util.DeleteTaskFile(util.ACTIVITY_CAPTURING_ARCHIVES)
 
         if *chromiumBuild == "" {
                 glog.Error("Must specify --chromium_build")
                 return
         }
 
+        // Reset the local chromium checkout.
+        if err := util.ResetCheckout(util.ChromiumSrcDir); err != nil {
+                glog.Errorf("Could not reset %s: %s", util.ChromiumSrcDir, err)
+                return
+        }
         // Sync the local chromium checkout.
         if err := util.SyncDir(util.ChromiumSrcDir); err != nil {
                 glog.Errorf("Could not gclient sync %s: %s", util.ChromiumSrcDir, err)
                 return
         }
 
         // Delete and remake the local webpage archives directory.
         pathToArchives := filepath.Join(util.WebArchivesDir, *pagesetType)
         skutil.RemoveAll(pathToArchives)
         skutil.MkdirAll(pathToArchives, 0700)
@@ skipping 55 matching lines @@
 
         // Write timestamp to the webpage archives dir.
         skutil.LogErr(util.CreateTimestampFile(pathToArchives))
 
         // Upload webpage archives dir to Google Storage.
         if err := gs.UploadWorkerArtifacts(util.WEB_ARCHIVES_DIR_NAME, *pagesetType, *workerNum); err != nil {
                 glog.Error(err)
                 return
         }
 }