Start EmbeddedWorker during registration - take 2

This adds the starting of the server worker to the registration
job pipeline. Eventually this will also dispatch the 'install'
event.

A second version of this, based on kinuko's work

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=249544

Review URL: https://codereview.chromium.org/140743012

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@249828 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 249828