Clean-up: Replaces Font with FontList in TooltipManager.

Clean-up: Replaces Font with FontList in TooltipManager.

This is a part of refactoring to replace all use of gfx::Font with gfx::FontList.  Also this replacement solves a possible vertical alignment issue of text rendering.

See "Background & Problem" section in the following doc why this refactoring is needed.
https://docs.google.com/a/chromium.org/document/d/1D_25fp9B8b9aZJORfAjDIFq61NWvUquZ5xmKH-VcC4k/edit#heading=h.olbd4u4vk3h6

NOTE:
a) Existing Font::GetStringWidth() is now obsolete and should be replaced by gfx::GetStringWidth() in ui/gfx/text_utils.h .
b) 'const' has internal linkage so it doesn't require anonymous namespace (in ui/views/widget/tooltip_manager.cc).

BUG=265485
TEST=Run unittests.

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=220509

[Yuki, 2013-08-29 12:32:40]

Could you guys review this CL as owners of ui/views/ and
chrome/browser/ui/views/bookmarks/ ?

Thanks in advance,
Yuki Shiino

[sky, 2013-08-29 15:44:29]

LGTM

[sadrul, 2013-08-29 16:54:59]

LGTM

[commit-bot: I haz the power, 2013-08-30 02:05:04]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/yukishiino@chromium.org/23483015/1

[commit-bot: I haz the power, 2013-08-30 05:36:52]

Change committed as 220509