Adds url to gclient json (try 2)
Adds url to gclient json (try 2)

Reland of https://codereview.chromium.org/268373003/ with a fix (wraps the
url with str())
https://codereview.chromium.org/268393002/ (bot_update root@revision support) is dependent on this

BUG=370503
TEST= gclient sync --output-json ~/tmp/asdfasdf.json on both an SVN and Git checkout

Review URL: https://codereview.chromium.org/277553002

git-svn-id: bd64dd6fa6f3f0ed0c0666d1018379882b742947@269469 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

svn2github/chromium-depot-tools,svn2github/chromium-depot-tools,svn2github/chromium-depot-tools