Initialize NativeThemeWin web instance with the system color info

This CL resolves a bug that prevents some users from seeing web
contents in High Contrast themes. Prior to CL:5081941, which improved
the way the web native theme is updated, the web instance for
NativeThemeWin was initialized with the system color info
unconditionally. The CL introduced conditions that resulted in the
NativeThemeWin web instance not picking up the right states when those
conditions are not met.

This CL fixes this by reverting back to the previous behavior of
unconditionally initializing the Windows native theme web instance
with the system color info.

Bug: 323898907
Change-Id: I1af3585f8787819a36025678c00f8b8d5dc0141d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5270616
Reviewed-by: Peter Kasting <pkasting@chromium.org>
Reviewed-by: Benjamin Beaudry <benjamin.beaudry@microsoft.com>
Commit-Queue: Sam Davis Omekara <samomekarajr@microsoft.com>
Cr-Commit-Position: refs/heads/main@{#1257578}