Devtools tests: inspector/* times out when run after inspector-protocol/*

BUG=305027
TBR=vsevik

Review URL: https://codereview.chromium.org/26476004

git-svn-id: svn://svn.chromium.org/blink/trunk@159140 bbb929c8-8fbe-4397-9dbb-9b2b20218538