[MD] Implement incognito colors as a NativeTheme (for Aura).

ui/views/widget/widget.cc

Index: ui/views/widget/widget.cc
diff --git a/ui/views/widget/widget.cc b/ui/views/widget/widget.cc
index c3c0252a7f91fe0a645dfa7be4deed08055e4bd7..a770f0f029167ee60d4675e82ea65ceb1997a307 100644
--- a/ui/views/widget/widget.cc
+++ b/ui/views/widget/widget.cc
@@ -766,6 +766,12 @@ ui::ThemeProvider* Widget::GetThemeProvider() const {
 }
 
 const ui::NativeTheme* Widget::GetNativeTheme() const {
+  if (ViewsDelegate::GetInstance()) {
+    ui::NativeTheme* theme =
+        ViewsDelegate::GetInstance()->GetNativeThemeOverride(this);

[sky, 2015/11/12 21:58:29]

Can we cache this rather than querying the delegate every time?

[Evan Stade, 2015/11/12 22:11:11]

I suppose we could as long as we call NativeTheme::NotifyObservers whenever the
theme changes.

+    if (theme)
+      return theme;
+  }
   return native_widget_->GetNativeTheme();
 }