Use correct font for label in a drag image

The drag image, generated when dragging a link from web contents is
using the same font for both the title and its link, even though
different fonts (bold and regular) are created for those two elements
(accordingly). This change makes the title use the bold font as it is
supposed to do.

R=eae@chromium.org

Review URL: https://codereview.chromium.org/517193002

git-svn-id: svn://svn.chromium.org/blink/trunk@181293 bbb929c8-8fbe-4397-9dbb-9b2b20218538