Update checks on when to add kColorSetNative in ColorMixer for macOS.

This CL makes the native color set visible if either macOS is running
on versions higher than 10.14 or if we are in light mode.

This fixes the case when secondary windows in Incognito which are
running on macOS versions < 10.14 can result in dark text on dark
background.

Bug: 1253530
Change-Id: I8e3b61a5751ad285d31c8e136c88701b8ed8f0e5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3233101
Commit-Queue: Rohit Agarwal <roagarwal@chromium.org>
Reviewed-by: Elly Fong-Jones <ellyjones@chromium.org>
Reviewed-by: Thomas Lukaszewicz <tluk@chromium.org>
Cr-Commit-Position: refs/heads/main@{#939993}

ui/color/mac/native_color_mixers_mac.mm

@@ -51,11 +51,7 @@ void AddNativeCoreColorMixer(ColorProvider* provider,
                 }});
 }
 
-void AddNativeUiColorMixer(ColorProvider* provider,
-                           bool dark_window,
-                           bool high_contrast) {
-  ScopedCurrentNSAppearance scoped_nsappearance(dark_window, high_contrast);
-  ColorMixer& mixer = provider->AddMixer();
+void AddNativeColorSetInColorMixer(ColorMixer& mixer) {
   mixer.AddSet(
       {kColorSetNative,
        {
@@ -65,6 +61,21 @@ void AddNativeUiColorMixer(ColorProvider* provider,
            {kColorMenuItemForeground,
             skia::NSSystemColorToSkColor([NSColor controlTextColor])},
        }});
+}
+
+void AddNativeUiColorMixer(ColorProvider* provider,
+                           bool dark_window,
+                           bool high_contrast) {
+  ScopedCurrentNSAppearance scoped_nsappearance(dark_window, high_contrast);
+  ColorMixer& mixer = provider->AddMixer();
+
+  // TODO(crbug.com/1268521): Investigate native color set behaviour for dark
+  // windows on macOS versions running < 10.14.
+  if (@available(macOS 10.14, *)) {
+    AddNativeColorSetInColorMixer(mixer);
+  } else if (!dark_window) {
+    AddNativeColorSetInColorMixer(mixer);
+  }
 
   if (@available(macOS 10.14, *)) {
     mixer[kColorTableBackgroundAlternate] = {skia::NSSystemColorToSkColor(