Revert of DevTools: [CodeMirrro] defer autocomplete controller initialization (patchset #2 id:20001 of https://codereview.chromium.org/670163002/)

Reason for revert:
Breaks autocomplete (only ctrl+space works)

Original issue's description:
> DevTools: [CodeMirrro] defer autocomplete controller initialization
> 
> Autocompletion controller intialization makes almost half of the time
> of SourceFrame initialization.
> 
> In order to render editor as fast as possible, this patch defers
> autocompletion initialization until the first need.
> 
> BUG=425550
> R=vsevik
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=184263

TBR=lushnikov@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=425550

Review URL: https://codereview.chromium.org/676393003

git-svn-id: svn://svn.chromium.org/blink/trunk@184451 bbb929c8-8fbe-4397-9dbb-9b2b20218538