[chromium] Fat scrollbars on Windows in high-DPI mode.
https://bugs.webkit.org/show_bug.cgi?id=108637

Updates mechanism for retrieving scrollbar metrics on the
Windows port of Chromium.  Previously, GetSystemMetrics calls
were used, which fetches prescaled sizes in pixel rather than
logical units, resulting in a double scaling when a device
scale factor is set.  With the patch, the size is retrieved
from the theme engine in DIP.

Patch by Kevin Ellis <kevers@chromium.org> on 2013-02-01
Reviewed by Adam Barth.

Source/Platform:

* chromium/public/win/WebThemeEngine.h:
(WebThemeEngine):

Source/WebCore:

No new tests.

* platform/chromium/ScrollbarThemeChromiumWin.cpp:
(WebCore::ScrollbarThemeChromiumWin::scrollbarThickness):
(WebCore::ScrollbarThemeChromiumWin::paintTrackPiece):
* rendering/RenderThemeChromiumWin.cpp:
(WebCore):
(WebCore::menuListButtonWidth):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@141652 268f45cc-cd09-0410-ab3c-d52691b4dbfc