Fix BookmarkBarControllerTest.LastBookmarkResizeBehavior on 10.11
Due to font width changes from <=10.9 (Lucida Grande), 10.10 (Helvetica), and 10.11 (San Francisco), different reference widths are used to determine whether the bookmark bar should overflow. San Francisco's font width is close enough to Lucida Grande's so change the logic to only use Yosemite widths for Yosemite and not Yosemite and each subsequent release.
BUG=none
TEST=BookmarkBarControllerTest.LastBookmarkResizeBehavior
Review URL: https://codereview.chromium.org/
1277823004
Cr-Commit-Position: refs/heads/master@{#342250}