Reland "Dont use NativeThemeFluent when OverlayScrollbars are on."

This reverts commit 7b9174f6ba.

Reason for revert: Wrongly reverted CL.

Original change's description:
> Revert "Dont use NativeThemeFluent when OverlayScrollbars are on."
>
> This reverts commit 3642e73760.
>
> Reason for revert: Suspecting causing the failure for virtual/percent-based-scrolling/max-percent-delta.html (https://ci.chromium.org/ui/p/chromium/builders/ci/Mac12%20Tests/11844/overview). Regression range: ba38d1639d..0d3dc9c6e9?pretty=fuller&n=
>
> Original change's description:
> > Dont use NativeThemeFluent when OverlayScrollbars are on.
> >
> > Overlay Scrollbars (enabled via chrome://flags or command line argument
> > --enable-features=OverlaySCrollbar) use NativeThemeAura; if they are
> > enabled we shouldn't use Fluent Scrollbar's Native Theme. With this
> > change, if both flags are enabled Overlay Scrollbars take precedence.
> >
> > Bug: 1470404
> > Change-Id: If329bad60daf7b7c2d6115b64de404750b12407e
> > Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4763424
> > Reviewed-by: Peter Kasting <pkasting@chromium.org>
> > Commit-Queue: Peter Kasting <pkasting@chromium.org>
> > Cr-Commit-Position: refs/heads/main@{#1181563}
>
> Bug: 1470404
> Change-Id: I17721e7eadacb1fc29c89b419742c9c4d70fc56e
> No-Presubmit: true
> No-Tree-Checks: true
> No-Try: true
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4765948
> Owners-Override: Jack Hsieh <chengweih@chromium.org>
> Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
> Commit-Queue: Jack Hsieh <chengweih@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#1181714}

Bug: 1470404
Change-Id: I9ca21659681cd5341ae3aa5c291605b6d420ef69
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4766202
Reviewed-by: Peter Kasting <pkasting@chromium.org>
Reviewed-by: Jack Hsieh <chengweih@chromium.org>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Commit-Queue: Gaston Rodriguez <gastonr@microsoft.com>
Owners-Override: Jack Hsieh <chengweih@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1181748}

ui/native_theme/native_theme_aura.cc

@@ -57,8 +57,9 @@ const SkScalar kScrollRadius =
 // static
 NativeTheme* NativeTheme::GetInstanceForWeb() {
 #if BUILDFLAG(IS_WIN)
-  if (IsFluentScrollbarEnabled())
+  if (IsFluentScrollbarEnabled() && !IsOverlayScrollbarEnabled()) {
     return NativeThemeFluent::web_instance();
+  }
 #endif  // BUILDFLAG(IS_WIN)
   return NativeThemeAura::web_instance();
 }