Revert of Add blink-side plumbing for ServiceWorker -> Document postMessage (1/3) (https://codereview.chromium.org/263143004/)

Reason for revert:
Speculative revert in order of fixing crashes in content_browsertests

Original issue's description:
> Add blink-side plumbing for ServiceWorker -> Document postMessage
> 
> - Initialize NavigatorServiceWorker and ServiceWorkerContainer earlier, right after a document is available (for Documents)
> - Add public interfaces:
> -- WebServiceWorkerContextClient.postMessageToClient()
> -- WebServiceWorkerProviderClient.dispatchMessageEvent()
> 
> This is the first patch for postMessage plumbing: 
> 1/3: THIS PATCH
> 2/3: https://codereview.chromium.org/246023007/ (chromium) 
> 3/3: https://codereview.chromium.org/264233003/ (blink, adds Layout test)
> 
> BUG=366063
> TEST=to be added after chromium-side change is landed
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=173495

TBR=jsbell@chromium.org,jochen@chromium.org,kinuko@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=366063

Review URL: https://codereview.chromium.org/270303004

git-svn-id: svn://svn.chromium.org/blink/trunk@173523 bbb929c8-8fbe-4397-9dbb-9b2b20218538