Fix bookmark button text directionality and eliding.

Fix bookmark button text directionality and eliding.

r278156 changed these buttons to LabelButton instances.

Make these buttons respect their text directionality.
Add LabelButton::SetDirectionalityMode to fix the Label.
Respect forced directionality in Canvas::DrawFadedString.
(still need to align with UI for text/icon placement)
(I might change this pattern in the future)

Use fade eliding on Linux, but ellipsis eliding on Win.
(the text looks bad faded on Win due to Issue 388084)

See bookmark_fading_and_alignment_fix_PS2b[_linux].png at
http://crbug.com/388086#c3 and http://crbug.com/388086#c4

BUG=388086,388084
TEST=Long RTL bookmarks elide correctly, look good.
R=sky@chromium.org

Review URL: https://codereview.chromium.org/350813002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@279863 0039d316-1c4b-4281-b951-d872f2087c98