Revert 158684 "Fix creating InjectedScript too early causing ext..."

> Fix creating InjectedScript too early causing extension bindings not to work.
> 
> BUG=263162
> TEST=manual
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=155947
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=156062
> 
> Review URL: https://codereview.chromium.org/22884002

TBR=tengs@chromium.org

Review URL: https://codereview.chromium.org/26063002

git-svn-id: svn://svn.chromium.org/blink/trunk@158963 bbb929c8-8fbe-4397-9dbb-9b2b20218538