DevTools: [SSP] bring autocompletion instantly for properties editing

This patch removes the 250ms delay before running autocompletion for
properties.

BUG=411021
R=vsevik, apavlov

Review URL: https://codereview.chromium.org/602493004

git-svn-id: svn://svn.chromium.org/blink/trunk@182960 bbb929c8-8fbe-4397-9dbb-9b2b20218538