all code
update
update
continue waiting 1s if urlfetch over quota in 1 min
Add X-Range Header if range fetch failed
Add 'src/' from commit 'fa885b38337d91064da3a804ea54a9e934db5215'

git-subtree-dir: src
git-subtree-mainline: 7afe8fce09f9bd4fb3f261622abcf563ed22891a
git-subtree-split: fa885b38337d91064da3a804ea54a9e934db5215
initial rearrangement