GitLab

This CL:
- Moves background.js to background.html
- Introduces remoting.appLauncher that allows the caller to launch and close the webapp without knowing the implementation difference between a v1 app and a v2 app.

NOTRY=true
R=jamiewalch@chromium.org

Review URL: https://codereview.chromium.org/450383003

Cr-Commit-Position: refs/heads/master@{#289096}
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@289096 0039d316-1c4b-4281-b951-d872f2087c98