Revert of Wire InstallFinished and add some InstallEvent.waitUntil tests (https://codereview.chromium.org/153553008/)

Reason for revert:
Suspect cause for failing content_browsertests:ServiceWorkerVersionBrowserTests

Original issue's description:
> Wire InstallFinished and add some InstallEvent.waitUntil tests
> 
> BUG=285976
> TEST=content_browsertests:ServiceWorkerVersionBrowserTest.Install*
> 
> Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=250804

TBR=alecflett@chromium.org,kinuko@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=285976

Review URL: https://codereview.chromium.org/147903008

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@250886 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 250886