Fix color of "i" on message level icon.

Fix show/hide sidebar icons alignment.
Remove empty text spans.
Cleanup SVG file.

BUG=

Review URL: https://codereview.chromium.org/107353006

git-svn-id: svn://svn.chromium.org/blink/trunk@164079 bbb929c8-8fbe-4397-9dbb-9b2b20218538