themes: constrain IncreasedContrastThemeSupplier to refresh-only

The inverted background tab design doesn't work at all with pre-Refresh tabs.

Bug: 870844
Change-Id: I598b92ed8d6e8fa8b586166fb7352df1d13c8360
Reviewed-on: https://chromium-review.googlesource.com/1163316Reviewed-by: Evan Stade <estade@chromium.org>
Commit-Queue: Elly Fong-Jones <ellyjones@chromium.org>
Cr-Commit-Position: refs/heads/master@{#581361}

chrome/browser/themes/theme_service.cc

@@ -340,8 +340,11 @@ void ThemeService::UseDefaultTheme() {
   }
 #endif
   ui::NativeTheme* native_theme = ui::NativeTheme::GetInstanceForNativeUi();
-  if (native_theme && native_theme->UsesHighContrastColors())
+  // IncreasedContrastThemeSupplier is designed for the Refresh UI only.
+  if (native_theme && native_theme->UsesHighContrastColors() &&
+      ui::MaterialDesignController::IsRefreshUi()) {
     SetCustomDefaultTheme(new IncreasedContrastThemeSupplier);
+  }
   ClearAllThemeData();
   NotifyThemeChanged();
 }