Make RenderTextWin fallback match original font heights.

ABANDONED: THIS SHRINKS I18N FONTS UNREASONABLY; SEE BUG.

Make RenderTextWin fallback match original font heights.

Fixes browser UI Hindi text clipping in EN-US locales, etc.
(if the system's default font doesn't support Hindi glyphs)
(fallback previously yielded text too tall for UI controls)
(shouldn't affect Chrome on Hindi Windows installations)

See before/after pics at http://crbug.com/404999#c17

BUG=404999
TEST=Chrome --lang=hi on EN-US Win, etc. looks okay.
R=sky@chromium.org,asvitkine@chromium.org

[msw, 2014-08-25 18:58:54]

msw@chromium.org changed reviewers:
+ sky@chromium.org

[msw, 2014-08-25 19:08:28]

msw@chromium.org changed reviewers:
+ asvitkine@chromium.org

[msw, 2014-08-25 19:10:11]

Hey Scott and Alexei, please take a look; thanks!

[Alexei Svitkine (slow), 2014-08-25 22:39:37]

The code itself looks good.

Two questions, though:

1. Back when I implemented the original logic, I distinctly remember non-XP
needing to derive based on size, otherwise the results wouldn't match the
original GDI code. Is this not the case? Have you checked it doesn't result in
incorrect size in other contexts? e.g. CJK languages

2. The non-XP path had a performance optimization where it wouldn't do anything
if the requested values already matched. Have you checked that this doesn't
cause a noticeable performance regression?