Revert of Start EmbeddedWorker during registration - take 2 (https://codereview.chromium.org/140743012/)

Reason for revert:
Makes virtual/serviceworker/http/tests/serviceworker/registration.html crash.
See http://build.chromium.org/p/chromium.webkit/builders/WebKit%20Linux/builds/26615

Original issue's description:
> 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

TBR=kinuko@chromium.org,alecflett@chromium.org
NOTREECHECKS=true
NOTRY=true

Review URL: https://codereview.chromium.org/137233019

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@249674 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 249674