BUG=168676 (part 2 of comment 0)
TEST=have enough bookmarks that the overflow chevron shows up.
observer it's now centered vertically.
TBR=sail

Review URL: https://codereview.chromium.org/11820007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@175610 0039d316-1c4b-4281-b951-d872f2087c98