Fix dark mode colors being used for alert icons in light mode.

The ternary operator here was backwards, with light mode colors being used
when the system is in dark mode, and vice versa.

Change-Id: Id6788f601a4cd741fb6ddce6ebe1aeb8fb44f1eb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1933386
Auto-Submit: Daniel Rubery <drubery@chromium.org>
Reviewed-by: Thomas Anderson <thomasanderson@chromium.org>
Commit-Queue: Thomas Anderson <thomasanderson@chromium.org>
Cr-Commit-Position: refs/heads/master@{#718800}

chrome/browser/ui/libgtkui/native_theme_gtk.cc

@@ -295,8 +295,8 @@ SkColor SkColorFromColorId(ui::NativeTheme::ColorId color_id) {
       // theme should be used.
       ui::NativeTheme* fallback_theme =
           color_utils::IsDark(GetBgColor(""))
-              ? ui::NativeTheme::GetInstanceForNativeUi()
-              : ui::NativeThemeDarkAura::instance();
+              ? ui::NativeThemeDarkAura::instance()
+              : ui::NativeTheme::GetInstanceForNativeUi();
       return fallback_theme->GetSystemColor(color_id);
     }