browser: reset the "content" color via `color: inherit`
browser: reset the "content" color via `color: inherit`

Necessary for Firefox v31, which seems to retain the previous
color from a previous %c color formatter when an empty string
is given.

visionmedia/debug,elliottsj/debug,CantemoInternal/debug,jabaz/debug,jabaz/debug,zacronos/debug,zacronos/debug,CantemoInternal/debug,elliottsj/debug