Move kAssociatedNetworkFontStyle out of browser_defaults

defaults.h defines various defaults whose values varies depending upon
the OS. kAssociatedNetworkFontStyle is only used in one file, on
ChromeOS, so doesn't belong.

(It was added in r89427 when there was a TOUCH_UI #ifdef, but that's
gone now).

BUG=None

Review URL: https://codereview.chromium.org/1379523002

Cr-Commit-Position: refs/heads/master@{#351432}
7 files changed