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

ct/go/master_scripts/build_chromium/main.go

 // Application that builds chromium with or without patches and uploads the build
 // to Google Storage.
 package main
 
 import (
         "flag"
         "fmt"
         "time"
 
         "github.com/skia-dev/glog"
@@ skipping 72 matching lines @@
 
         if *chromiumHash == "" {
                 glog.Error("Must specify --chromium_hash")
                 return
         }
         if *skiaHash == "" {
                 glog.Error("Must specify --skia_hash")
                 return
         }
 
-        if _, _, err := util.CreateChromiumBuild("", *targetPlatform, *chromiumHash, *skiaHash, *applyPatches); err != nil {
+        if _, _, err := util.CreateChromiumBuild("", *targetPlatform, *chromiumHash, *skiaHash, *applyPatches, false); err != nil {

[dogben, 2016/05/18 14:29:37]

Seems like this always would want to upload just a single build with patches?

So, would it make sense for CreateChromiumBuild to not build the unpatched
version if both applyPatches and uploadSingleBuild are true?

[rmistry, 2016/05/19 11:21:00]

The (applyPatches && !uploadSingleBuild) was confusing so I now just check for
!uploadSingleBuild. This means that if applyPatches is false and
uploadSingleBuild is false then two patchless builds will be created and
uploaded, we do not have a usecase for this yet but does not hurt to have the
ability to do that.

[dogben, 2016/05/19 14:09:08]

Oh, I see. I was confused, but the new code is less confusing. :-)

                 glog.Errorf("Error while creating the Chromium build: %s", err)
                 return
         }
 
         taskCompletedSuccessfully = true
 }