Add ability to only upload a single Chromium build and check for patch existence

ct/go/master_scripts/run_chromium_perf_on_workers/main.go

 // run_chromium_perf_on_workers is an application that runs the specified telemetry
 // benchmark on all CT workers and uploads the results to Google Storage. The
 // requester is emailed when the task is done.
 package main
 
 import (
         "bytes"
         "database/sql"
         "flag"
         "fmt"
@@ skipping 147 matching lines @@
                 if err := gs.UploadFile(patchName, os.TempDir(), remoteOutputDir); err != nil {
                         glog.Errorf("Could not upload %s to %s: %s", patchName, remoteOutputDir, err)
                         return
                 }
         }
         skiaPatchLink = util.GS_HTTP_LINK + filepath.Join(util.GSBucketName, remoteOutputDir, skiaPatchName)
         chromiumPatchLink = util.GS_HTTP_LINK + filepath.Join(util.GSBucketName, remoteOutputDir, chromiumPatchName)
         benchmarkPatchLink = util.GS_HTTP_LINK + filepath.Join(util.GSBucketName, remoteOutputDir, benchmarkPatchName)
 
         // Create the two required chromium builds (with patch and without the patch).
-        chromiumHash, skiaHash, err := util.CreateChromiumBuild(*runID, *targetPlatform, "", "", true)
+        chromiumHash, skiaHash, err := util.CreateChromiumBuild(*runID, *targetPlatform, "", "", true, false)
         if err != nil {
                 glog.Errorf("Could not create chromium build: %s", err)
                 return
         }
 
         // Reboot all workers to start from a clean slate.
         if !*master_common.Local {
                 util.RebootWorkers()
         }
 
@@ skipping 182 matching lines @@
         if err != nil {
                 return noOutputSlaves, fmt.Errorf("Error running csv_merger.py: %s", err)
         }
         // Copy the output file to Google Storage.
         remoteOutputDir := filepath.Join(util.BenchmarkRunsDir, runID, "consolidated_outputs")
         if err := gs.UploadFile(outputFileName, localOutputDir, remoteOutputDir); err != nil {
                 return noOutputSlaves, fmt.Errorf("Unable to upload %s to %s: %s", outputFileName, remoteOutputDir, err)
         }
         return noOutputSlaves, nil
 }