DevTools: separate style for error message bubble.

This patch separates style used for error message repeat count bubble
in console. The style is already used in Resources panel, and will be
used later for editor errors.

BUG=397217
R=vsevik, apavlov
NOTRY=true

Review URL: https://codereview.chromium.org/428563002

git-svn-id: svn://svn.chromium.org/blink/trunk@179108 bbb929c8-8fbe-4397-9dbb-9b2b20218538