Use 10 threads instead of 1 while uploading screenshots

Bug: 842913
Change-Id: I834c962a21faeb53cb64acb4a4202cf7cfe0af9e
Reviewed-on: https://chromium-review.googlesource.com/1149185
Commit-Queue: Mustafa Emre Acer <meacer@chromium.org>
Reviewed-by: anthonyvd <anthonyvd@chromium.org>
Cr-Commit-Position: refs/heads/master@{#579457}

tools/translation/upload_screenshots.py

@@ -176,7 +176,7 @@ def main():
         gsutil=gsutil,
         force=False,
         use_md5=False,
-        num_threads=1,
+        num_threads=10,
         skip_hashing=False,
         gzip=None) != 0:
       print 'Error uploading screenshots, exiting.'